diff --git a/llvm/lib/Support/FileCheck.cpp b/llvm/lib/Support/FileCheck.cpp
index fb4bbba..c3f537b 100644
--- a/llvm/lib/Support/FileCheck.cpp
+++ b/llvm/lib/Support/FileCheck.cpp
@@ -1,1990 +1,1985 @@
-//===- FileCheck.cpp - Check that File's Contents match what is expected --===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-//
-// FileCheck does a line-by line check of a file that validates whether it
-// contains the expected content.  This is useful for regression tests etc.
-//
-// This file implements most of the API that will be used by the FileCheck utility
-// as well as various unittests.
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Support/FileCheck.h"
-#include "FileCheckImpl.h"
-#include "llvm/ADT/StringSet.h"
-#include "llvm/ADT/Twine.h"
-#include "llvm/Support/FormatVariadic.h"
-#include <cstdint>
-#include <list>
-#include <tuple>
-#include <utility>
-
-using namespace llvm;
-
-Expected<uint64_t> FileCheckNumericVariableUse::eval() const {
-  Optional<uint64_t> Value = NumericVariable->getValue();
-  if (Value)
-    return *Value;
-
-  return make_error<FileCheckUndefVarError>(Name);
-}
-
-Expected<uint64_t> FileCheckASTBinop::eval() const {
-  Expected<uint64_t> LeftOp = LeftOperand->eval();
-  Expected<uint64_t> RightOp = RightOperand->eval();
-
-  // Bubble up any error (e.g. undefined variables) in the recursive
-  // evaluation.
-  if (!LeftOp || !RightOp) {
-    Error Err = Error::success();
-    if (!LeftOp)
-      Err = joinErrors(std::move(Err), LeftOp.takeError());
-    if (!RightOp)
-      Err = joinErrors(std::move(Err), RightOp.takeError());
-    return std::move(Err);
-  }
-
-  return EvalBinop(*LeftOp, *RightOp);
-}
-
-Expected<std::string> FileCheckNumericSubstitution::getResult() const {
-  Expected<uint64_t> EvaluatedValue = ExpressionAST->eval();
-  if (!EvaluatedValue)
-    return EvaluatedValue.takeError();
-  return utostr(*EvaluatedValue);
-}
-
-Expected<std::string> FileCheckStringSubstitution::getResult() const {
-  // Look up the value and escape it so that we can put it into the regex.
-  Expected<StringRef> VarVal = Context->getPatternVarValue(FromStr);
-  if (!VarVal)
-    return VarVal.takeError();
-  return Regex::escape(*VarVal);
-}
-
-bool FileCheckPattern::isValidVarNameStart(char C) {
-  return C == '_' || isalpha(C);
-}
-
-Expected<FileCheckPattern::VariableProperties>
-FileCheckPattern::parseVariable(StringRef &Str, const SourceMgr &SM) {
-  if (Str.empty())
-    return FileCheckErrorDiagnostic::get(SM, Str, "empty variable name");
-
-  bool ParsedOneChar = false;
-  unsigned I = 0;
-  bool IsPseudo = Str[0] == '@';
-
-  // Global vars start with '$'.
-  if (Str[0] == '$' || IsPseudo)
-    ++I;
-
-  for (unsigned E = Str.size(); I != E; ++I) {
-    if (!ParsedOneChar && !isValidVarNameStart(Str[I]))
-      return FileCheckErrorDiagnostic::get(SM, Str, "invalid variable name");
-
-    // Variable names are composed of alphanumeric characters and underscores.
-    if (Str[I] != '_' && !isalnum(Str[I]))
-      break;
-    ParsedOneChar = true;
-  }
-
-  StringRef Name = Str.take_front(I);
-  Str = Str.substr(I);
-  return VariableProperties {Name, IsPseudo};
-}
-
-// StringRef holding all characters considered as horizontal whitespaces by
-// FileCheck input canonicalization.
-constexpr StringLiteral SpaceChars = " \t";
-
-// Parsing helper function that strips the first character in S and returns it.
-static char popFront(StringRef &S) {
-  char C = S.front();
-  S = S.drop_front();
-  return C;
-}
-
-char FileCheckUndefVarError::ID = 0;
-char FileCheckErrorDiagnostic::ID = 0;
-char FileCheckNotFoundError::ID = 0;
-
-Expected<FileCheckNumericVariable *>
-FileCheckPattern::parseNumericVariableDefinition(
-    StringRef &Expr, FileCheckPatternContext *Context,
-    Optional<size_t> LineNumber, const SourceMgr &SM) {
-  Expected<VariableProperties> ParseVarResult = parseVariable(Expr, SM);
-  if (!ParseVarResult)
-    return ParseVarResult.takeError();
-  StringRef Name = ParseVarResult->Name;
-
-  if (ParseVarResult->IsPseudo)
-    return FileCheckErrorDiagnostic::get(
-        SM, Name, "definition of pseudo numeric variable unsupported");
-
-  // Detect collisions between string and numeric variables when the latter
-  // is created later than the former.
-  if (Context->DefinedVariableTable.find(Name) !=
-      Context->DefinedVariableTable.end())
-    return FileCheckErrorDiagnostic::get(
-        SM, Name, "string variable with name '" + Name + "' already exists");
-
-  Expr = Expr.ltrim(SpaceChars);
-  if (!Expr.empty())
-    return FileCheckErrorDiagnostic::get(
-        SM, Expr, "unexpected characters after numeric variable name");
-
-  FileCheckNumericVariable *DefinedNumericVariable;
-  auto VarTableIter = Context->GlobalNumericVariableTable.find(Name);
-  if (VarTableIter != Context->GlobalNumericVariableTable.end())
-    DefinedNumericVariable = VarTableIter->second;
-  else
-    DefinedNumericVariable = Context->makeNumericVariable(Name, LineNumber);
-
-  return DefinedNumericVariable;
-}
-
-Expected<std::unique_ptr<FileCheckNumericVariableUse>>
-FileCheckPattern::parseNumericVariableUse(StringRef Name, bool IsPseudo,
-                                          Optional<size_t> LineNumber,
-                                          FileCheckPatternContext *Context,
-                                          const SourceMgr &SM) {
-  if (IsPseudo && !Name.equals("@LINE"))
-    return FileCheckErrorDiagnostic::get(
-        SM, Name, "invalid pseudo numeric variable '" + Name + "'");
-
-  // Numeric variable definitions and uses are parsed in the order in which
-  // they appear in the CHECK patterns. For each definition, the pointer to the
-  // class instance of the corresponding numeric variable definition is stored
-  // in GlobalNumericVariableTable in parsePattern. Therefore, if the pointer
-  // we get below is null, it means no such variable was defined before. When
-  // that happens, we create a dummy variable so that parsing can continue. All
-  // uses of undefined variables, whether string or numeric, are then diagnosed
-  // in printSubstitutions() after failing to match.
-  auto VarTableIter = Context->GlobalNumericVariableTable.find(Name);
-  FileCheckNumericVariable *NumericVariable;
-  if (VarTableIter != Context->GlobalNumericVariableTable.end())
-    NumericVariable = VarTableIter->second;
-  else {
-    NumericVariable = Context->makeNumericVariable(Name);
-    Context->GlobalNumericVariableTable[Name] = NumericVariable;
-  }
-
-  Optional<size_t> DefLineNumber = NumericVariable->getDefLineNumber();
-  if (DefLineNumber && LineNumber && *DefLineNumber == *LineNumber)
-    return FileCheckErrorDiagnostic::get(
-        SM, Name,
-        "numeric variable '" + Name +
-            "' defined earlier in the same CHECK directive");
-
-  return std::make_unique<FileCheckNumericVariableUse>(Name, NumericVariable);
-}
-
-Expected<std::unique_ptr<FileCheckExpressionAST>>
-FileCheckPattern::parseNumericOperand(StringRef &Expr, AllowedOperand AO,
-                                      Optional<size_t> LineNumber,
-                                      FileCheckPatternContext *Context,
-                                      const SourceMgr &SM) {
-  if (AO == AllowedOperand::LineVar || AO == AllowedOperand::Any) {
-    // Try to parse as a numeric variable use.
-    Expected<FileCheckPattern::VariableProperties> ParseVarResult =
-        parseVariable(Expr, SM);
-    if (ParseVarResult)
-      return parseNumericVariableUse(ParseVarResult->Name,
-                                     ParseVarResult->IsPseudo, LineNumber,
-                                     Context, SM);
-    if (AO == AllowedOperand::LineVar)
-      return ParseVarResult.takeError();
-    // Ignore the error and retry parsing as a literal.
-    consumeError(ParseVarResult.takeError());
-  }
-
-  // Otherwise, parse it as a literal.
-  uint64_t LiteralValue;
-  if (!Expr.consumeInteger(/*Radix=*/10, LiteralValue))
-    return std::make_unique<FileCheckExpressionLiteral>(LiteralValue);
-
-  return FileCheckErrorDiagnostic::get(SM, Expr,
-                                       "invalid operand format '" + Expr + "'");
-}
-
-static uint64_t add(uint64_t LeftOp, uint64_t RightOp) {
-  return LeftOp + RightOp;
-}
-
-static uint64_t sub(uint64_t LeftOp, uint64_t RightOp) {
-  return LeftOp - RightOp;
-}
-
-Expected<std::unique_ptr<FileCheckExpressionAST>> FileCheckPattern::parseBinop(
-    StringRef &Expr, std::unique_ptr<FileCheckExpressionAST> LeftOp,
-    bool IsLegacyLineExpr, Optional<size_t> LineNumber,
-    FileCheckPatternContext *Context, const SourceMgr &SM) {
-  Expr = Expr.ltrim(SpaceChars);
-  if (Expr.empty())
-    return std::move(LeftOp);
-
-  // Check if this is a supported operation and select a function to perform
-  // it.
-  SMLoc OpLoc = SMLoc::getFromPointer(Expr.data());
-  char Operator = popFront(Expr);
-  binop_eval_t EvalBinop;
-  switch (Operator) {
-  case '+':
-    EvalBinop = add;
-    break;
-  case '-':
-    EvalBinop = sub;
-    break;
-  default:
-    return FileCheckErrorDiagnostic::get(
-        SM, OpLoc, Twine("unsupported operation '") + Twine(Operator) + "'");
-  }
-
-  // Parse right operand.
-  Expr = Expr.ltrim(SpaceChars);
-  if (Expr.empty())
-    return FileCheckErrorDiagnostic::get(SM, Expr,
-                                         "missing operand in expression");
-  // The second operand in a legacy @LINE expression is always a literal.
-  AllowedOperand AO =
-      IsLegacyLineExpr ? AllowedOperand::Literal : AllowedOperand::Any;
-  Expected<std::unique_ptr<FileCheckExpressionAST>> RightOpResult =
-      parseNumericOperand(Expr, AO, LineNumber, Context, SM);
-  if (!RightOpResult)
-    return RightOpResult;
-
-  Expr = Expr.ltrim(SpaceChars);
-  return std::make_unique<FileCheckASTBinop>(EvalBinop, std::move(LeftOp),
-                                              std::move(*RightOpResult));
-}
-
-Expected<std::unique_ptr<FileCheckExpressionAST>>
-FileCheckPattern::parseNumericSubstitutionBlock(
-    StringRef Expr,
-    Optional<FileCheckNumericVariable *> &DefinedNumericVariable,
-    bool IsLegacyLineExpr, Optional<size_t> LineNumber,
-    FileCheckPatternContext *Context, const SourceMgr &SM) {
-  std::unique_ptr<FileCheckExpressionAST> ExpressionAST = nullptr;
-  StringRef DefExpr = StringRef();
-  DefinedNumericVariable = None;
-  // Save variable definition expression if any.
-  size_t DefEnd = Expr.find(':');
-  if (DefEnd != StringRef::npos) {
-    DefExpr = Expr.substr(0, DefEnd);
-    Expr = Expr.substr(DefEnd + 1);
-  }
-
-  // Parse the expression itself.
-  Expr = Expr.ltrim(SpaceChars);
-  if (!Expr.empty()) {
-    // The first operand in a legacy @LINE expression is always the @LINE
-    // pseudo variable.
-    AllowedOperand AO =
-        IsLegacyLineExpr ? AllowedOperand::LineVar : AllowedOperand::Any;
-    Expected<std::unique_ptr<FileCheckExpressionAST>> ParseResult =
-        parseNumericOperand(Expr, AO, LineNumber, Context, SM);
-    while (ParseResult && !Expr.empty()) {
-      ParseResult = parseBinop(Expr, std::move(*ParseResult), IsLegacyLineExpr,
-                               LineNumber, Context, SM);
-      // Legacy @LINE expressions only allow 2 operands.
-      if (ParseResult && IsLegacyLineExpr && !Expr.empty())
-        return FileCheckErrorDiagnostic::get(
-            SM, Expr,
-            "unexpected characters at end of expression '" + Expr + "'");
-    }
-    if (!ParseResult)
-      return ParseResult;
-    ExpressionAST = std::move(*ParseResult);
-  }
-
-  // Parse the numeric variable definition.
-  if (DefEnd != StringRef::npos) {
-    DefExpr = DefExpr.ltrim(SpaceChars);
-    Expected<FileCheckNumericVariable *> ParseResult =
-        parseNumericVariableDefinition(DefExpr, Context, LineNumber, SM);
-
-    if (!ParseResult)
-      return ParseResult.takeError();
-    DefinedNumericVariable = *ParseResult;
-  }
-
-  return std::move(ExpressionAST);
-}
-
-bool FileCheckPattern::parsePattern(StringRef PatternStr, StringRef Prefix,
-                                    SourceMgr &SM,
-                                    const FileCheckRequest &Req) {
-  bool MatchFullLinesHere = Req.MatchFullLines && CheckTy != Check::CheckNot;
-  IgnoreCase = Req.IgnoreCase;
-
-  PatternLoc = SMLoc::getFromPointer(PatternStr.data());
-
-  if (!(Req.NoCanonicalizeWhiteSpace && Req.MatchFullLines))
-    // Ignore trailing whitespace.
-    while (!PatternStr.empty() &&
-           (PatternStr.back() == ' ' || PatternStr.back() == '\t'))
-      PatternStr = PatternStr.substr(0, PatternStr.size() - 1);
-
-  // Check that there is something on the line.
-  if (PatternStr.empty() && CheckTy != Check::CheckEmpty) {
-    SM.PrintMessage(PatternLoc, SourceMgr::DK_Error,
-                    "found empty check string with prefix '" + Prefix + ":'");
-    return true;
-  }
-
-  if (!PatternStr.empty() && CheckTy == Check::CheckEmpty) {
-    SM.PrintMessage(
-        PatternLoc, SourceMgr::DK_Error,
-        "found non-empty check string for empty check with prefix '" + Prefix +
-            ":'");
-    return true;
-  }
-
-  if (CheckTy == Check::CheckEmpty) {
-    RegExStr = "(\n$)";
-    return false;
-  }
-
-  // Check to see if this is a fixed string, or if it has regex pieces.
-  if (!MatchFullLinesHere &&
-      (PatternStr.size() < 2 || (PatternStr.find("{{") == StringRef::npos &&
-                                 PatternStr.find("[[") == StringRef::npos))) {
-    FixedStr = PatternStr;
-    return false;
-  }
-
-  if (MatchFullLinesHere) {
-    RegExStr += '^';
-    if (!Req.NoCanonicalizeWhiteSpace)
-      RegExStr += " *";
-  }
-
-  // Paren value #0 is for the fully matched string.  Any new parenthesized
-  // values add from there.
-  unsigned CurParen = 1;
-
-  // Otherwise, there is at least one regex piece.  Build up the regex pattern
-  // by escaping scary characters in fixed strings, building up one big regex.
-  while (!PatternStr.empty()) {
-    // RegEx matches.
-    if (PatternStr.startswith("{{")) {
-      // This is the start of a regex match.  Scan for the }}.
-      size_t End = PatternStr.find("}}");
-      if (End == StringRef::npos) {
-        SM.PrintMessage(SMLoc::getFromPointer(PatternStr.data()),
-                        SourceMgr::DK_Error,
-                        "found start of regex string with no end '}}'");
-        return true;
-      }
-
-      // Enclose {{}} patterns in parens just like [[]] even though we're not
-      // capturing the result for any purpose.  This is required in case the
-      // expression contains an alternation like: CHECK:  abc{{x|z}}def.  We
-      // want this to turn into: "abc(x|z)def" not "abcx|zdef".
-      RegExStr += '(';
-      ++CurParen;
-
-      if (AddRegExToRegEx(PatternStr.substr(2, End - 2), CurParen, SM))
-        return true;
-      RegExStr += ')';
-
-      PatternStr = PatternStr.substr(End + 2);
-      continue;
-    }
-
-    // String and numeric substitution blocks. Pattern substitution blocks come
-    // in two forms: [[foo:.*]] and [[foo]]. The former matches .* (or some
-    // other regex) and assigns it to the string variable 'foo'. The latter
-    // substitutes foo's value. Numeric substitution blocks recognize the same
-    // form as string ones, but start with a '#' sign after the double
-    // brackets. They also accept a combined form which sets a numeric variable
-    // to the evaluation of an expression. Both string and numeric variable
-    // names must satisfy the regular expression "[a-zA-Z_][0-9a-zA-Z_]*" to be
-    // valid, as this helps catch some common errors.
-    if (PatternStr.startswith("[[")) {
-      StringRef UnparsedPatternStr = PatternStr.substr(2);
-      // Find the closing bracket pair ending the match.  End is going to be an
-      // offset relative to the beginning of the match string.
-      size_t End = FindRegexVarEnd(UnparsedPatternStr, SM);
-      StringRef MatchStr = UnparsedPatternStr.substr(0, End);
-      bool IsNumBlock = MatchStr.consume_front("#");
-
-      if (End == StringRef::npos) {
-        SM.PrintMessage(SMLoc::getFromPointer(PatternStr.data()),
-                        SourceMgr::DK_Error,
-                        "Invalid substitution block, no ]] found");
-        return true;
-      }
-      // Strip the substitution block we are parsing. End points to the start
-      // of the "]]" closing the expression so account for it in computing the
-      // index of the first unparsed character.
-      PatternStr = UnparsedPatternStr.substr(End + 2);
-
-      bool IsDefinition = false;
-      bool SubstNeeded = false;
-      // Whether the substitution block is a legacy use of @LINE with string
-      // substitution block syntax.
-      bool IsLegacyLineExpr = false;
-      StringRef DefName;
-      StringRef SubstStr;
-      StringRef MatchRegexp;
-      size_t SubstInsertIdx = RegExStr.size();
-
-      // Parse string variable or legacy @LINE expression.
-      if (!IsNumBlock) {
-        size_t VarEndIdx = MatchStr.find(":");
-        size_t SpacePos = MatchStr.substr(0, VarEndIdx).find_first_of(" \t");
-        if (SpacePos != StringRef::npos) {
-          SM.PrintMessage(SMLoc::getFromPointer(MatchStr.data() + SpacePos),
-                          SourceMgr::DK_Error, "unexpected whitespace");
-          return true;
-        }
-
-        // Get the name (e.g. "foo") and verify it is well formed.
-        StringRef OrigMatchStr = MatchStr;
-        Expected<FileCheckPattern::VariableProperties> ParseVarResult =
-            parseVariable(MatchStr, SM);
-        if (!ParseVarResult) {
-          logAllUnhandledErrors(ParseVarResult.takeError(), errs());
-          return true;
-        }
-        StringRef Name = ParseVarResult->Name;
-        bool IsPseudo = ParseVarResult->IsPseudo;
-
-        IsDefinition = (VarEndIdx != StringRef::npos);
-        SubstNeeded = !IsDefinition;
-        if (IsDefinition) {
-          if ((IsPseudo || !MatchStr.consume_front(":"))) {
-            SM.PrintMessage(SMLoc::getFromPointer(Name.data()),
-                            SourceMgr::DK_Error,
-                            "invalid name in string variable definition");
-            return true;
-          }
-
-          // Detect collisions between string and numeric variables when the
-          // former is created later than the latter.
-          if (Context->GlobalNumericVariableTable.find(Name) !=
-              Context->GlobalNumericVariableTable.end()) {
-            SM.PrintMessage(
-                SMLoc::getFromPointer(Name.data()), SourceMgr::DK_Error,
-                "numeric variable with name '" + Name + "' already exists");
-            return true;
-          }
-          DefName = Name;
-          MatchRegexp = MatchStr;
-        } else {
-          if (IsPseudo) {
-            MatchStr = OrigMatchStr;
-            IsLegacyLineExpr = IsNumBlock = true;
-          } else
-            SubstStr = Name;
-        }
-      }
-
-      // Parse numeric substitution block.
-      std::unique_ptr<FileCheckExpressionAST> ExpressionAST;
-      Optional<FileCheckNumericVariable *> DefinedNumericVariable;
-      if (IsNumBlock) {
-        Expected<std::unique_ptr<FileCheckExpressionAST>> ParseResult =
-            parseNumericSubstitutionBlock(MatchStr, DefinedNumericVariable,
-                                          IsLegacyLineExpr, LineNumber, Context,
-                                          SM);
-        if (!ParseResult) {
-          logAllUnhandledErrors(ParseResult.takeError(), errs());
-          return true;
-        }
-        ExpressionAST = std::move(*ParseResult);
-        SubstNeeded = ExpressionAST != nullptr;
-        if (DefinedNumericVariable) {
-          IsDefinition = true;
-          DefName = (*DefinedNumericVariable)->getName();
-        }
-        if (SubstNeeded)
-          SubstStr = MatchStr;
-        else
-          MatchRegexp = "[0-9]+";
-      }
-
-      // Handle variable definition: [[<def>:(...)]] and [[#(...)<def>:(...)]].
-      if (IsDefinition) {
-        RegExStr += '(';
-        ++SubstInsertIdx;
-
-        if (IsNumBlock) {
-          FileCheckNumericVariableMatch NumericVariableDefinition = {
-              *DefinedNumericVariable, CurParen};
-          NumericVariableDefs[DefName] = NumericVariableDefinition;
-          // This store is done here rather than in match() to allow
-          // parseNumericVariableUse() to get the pointer to the class instance
-          // of the right variable definition corresponding to a given numeric
-          // variable use.
-          Context->GlobalNumericVariableTable[DefName] =
-              *DefinedNumericVariable;
-        } else {
-          VariableDefs[DefName] = CurParen;
-          // Mark string variable as defined to detect collisions between
-          // string and numeric variables in parseNumericVariableUse() and
-          // defineCmdlineVariables() when the latter is created later than the
-          // former. We cannot reuse GlobalVariableTable for this by populating
-          // it with an empty string since we would then lose the ability to
-          // detect the use of an undefined variable in match().
-          Context->DefinedVariableTable[DefName] = true;
-        }
-
-        ++CurParen;
-      }
-
-      if (!MatchRegexp.empty() && AddRegExToRegEx(MatchRegexp, CurParen, SM))
-        return true;
-
-      if (IsDefinition)
-        RegExStr += ')';
-
-      // Handle substitutions: [[foo]] and [[#<foo expr>]].
-      if (SubstNeeded) {
-        // Handle substitution of string variables that were defined earlier on
-        // the same line by emitting a backreference. Expressions do not
-        // support substituting a numeric variable defined on the same line.
-        if (!IsNumBlock && VariableDefs.find(SubstStr) != VariableDefs.end()) {
-          unsigned CaptureParenGroup = VariableDefs[SubstStr];
-          if (CaptureParenGroup < 1 || CaptureParenGroup > 9) {
-            SM.PrintMessage(SMLoc::getFromPointer(SubstStr.data()),
-                            SourceMgr::DK_Error,
-                            "Can't back-reference more than 9 variables");
-            return true;
-          }
-          AddBackrefToRegEx(CaptureParenGroup);
-        } else {
-          // Handle substitution of string variables ([[<var>]]) defined in
-          // previous CHECK patterns, and substitution of expressions.
-          FileCheckSubstitution *Substitution =
-              IsNumBlock
-                  ? Context->makeNumericSubstitution(
-                        SubstStr, std::move(ExpressionAST), SubstInsertIdx)
-                  : Context->makeStringSubstitution(SubstStr, SubstInsertIdx);
-          Substitutions.push_back(Substitution);
-        }
-      }
-    }
-
-    // Handle fixed string matches.
-    // Find the end, which is the start of the next regex.
-    size_t FixedMatchEnd = PatternStr.find("{{");
-    FixedMatchEnd = std::min(FixedMatchEnd, PatternStr.find("[["));
-    RegExStr += Regex::escape(PatternStr.substr(0, FixedMatchEnd));
-    PatternStr = PatternStr.substr(FixedMatchEnd);
-  }
-
-  if (MatchFullLinesHere) {
-    if (!Req.NoCanonicalizeWhiteSpace)
-      RegExStr += " *";
-    RegExStr += '$';
-  }
-
-  return false;
-}
-
-bool FileCheckPattern::AddRegExToRegEx(StringRef RS, unsigned &CurParen, SourceMgr &SM) {
-  Regex R(RS);
-  std::string Error;
-  if (!R.isValid(Error)) {
-    SM.PrintMessage(SMLoc::getFromPointer(RS.data()), SourceMgr::DK_Error,
-                    "invalid regex: " + Error);
-    return true;
-  }
-
-  RegExStr += RS.str();
-  CurParen += R.getNumMatches();
-  return false;
-}
-
-void FileCheckPattern::AddBackrefToRegEx(unsigned BackrefNum) {
-  assert(BackrefNum >= 1 && BackrefNum <= 9 && "Invalid backref number");
-  std::string Backref = std::string("\\") + std::string(1, '0' + BackrefNum);
-  RegExStr += Backref;
-}
-
-Expected<size_t> FileCheckPattern::match(StringRef Buffer, size_t &MatchLen,
-                                         const SourceMgr &SM) const {
-  // If this is the EOF pattern, match it immediately.
-  if (CheckTy == Check::CheckEOF) {
-    MatchLen = 0;
-    return Buffer.size();
-  }
-
-  // If this is a fixed string pattern, just match it now.
-  if (!FixedStr.empty()) {
-    MatchLen = FixedStr.size();
-    size_t Pos = IgnoreCase ? Buffer.find_lower(FixedStr)
-                            : Buffer.find(FixedStr);
-    if (Pos == StringRef::npos)
-      return make_error<FileCheckNotFoundError>();
-    return Pos;
-  }
-
-  // Regex match.
-
-  // If there are substitutions, we need to create a temporary string with the
-  // actual value.
-  StringRef RegExToMatch = RegExStr;
-  std::string TmpStr;
-  if (!Substitutions.empty()) {
-    TmpStr = RegExStr;
-    if (LineNumber)
-      Context->LineVariable->setValue(*LineNumber);
-
-    size_t InsertOffset = 0;
-    // Substitute all string variables and expressions whose values are only
-    // now known. Use of string variables defined on the same line are handled
-    // by back-references.
-    for (const auto &Substitution : Substitutions) {
-      // Substitute and check for failure (e.g. use of undefined variable).
-      Expected<std::string> Value = Substitution->getResult();
-      if (!Value)
-        return Value.takeError();
-
-      // Plop it into the regex at the adjusted offset.
-      TmpStr.insert(TmpStr.begin() + Substitution->getIndex() + InsertOffset,
-                    Value->begin(), Value->end());
-      InsertOffset += Value->size();
-    }
-
-    // Match the newly constructed regex.
-    RegExToMatch = TmpStr;
-  }
-
-  SmallVector<StringRef, 4> MatchInfo;
-  unsigned int Flags = Regex::Newline;
-  if (IgnoreCase)
-    Flags |= Regex::IgnoreCase;
-  if (!Regex(RegExToMatch, Flags).match(Buffer, &MatchInfo))
-    return make_error<FileCheckNotFoundError>();
-
-  // Successful regex match.
-  assert(!MatchInfo.empty() && "Didn't get any match");
-  StringRef FullMatch = MatchInfo[0];
-
-  // If this defines any string variables, remember their values.
-  for (const auto &VariableDef : VariableDefs) {
-    assert(VariableDef.second < MatchInfo.size() && "Internal paren error");
-    Context->GlobalVariableTable[VariableDef.first] =
-        MatchInfo[VariableDef.second];
-  }
-
-  // If this defines any numeric variables, remember their values.
-  for (const auto &NumericVariableDef : NumericVariableDefs) {
-    const FileCheckNumericVariableMatch &NumericVariableMatch =
-        NumericVariableDef.getValue();
-    unsigned CaptureParenGroup = NumericVariableMatch.CaptureParenGroup;
-    assert(CaptureParenGroup < MatchInfo.size() && "Internal paren error");
-    FileCheckNumericVariable *DefinedNumericVariable =
-        NumericVariableMatch.DefinedNumericVariable;
-
-    StringRef MatchedValue = MatchInfo[CaptureParenGroup];
-    uint64_t Val;
-    if (MatchedValue.getAsInteger(10, Val))
-      return FileCheckErrorDiagnostic::get(SM, MatchedValue,
-                                           "Unable to represent numeric value");
-    DefinedNumericVariable->setValue(Val);
-  }
-
-  // Like CHECK-NEXT, CHECK-EMPTY's match range is considered to start after
-  // the required preceding newline, which is consumed by the pattern in the
-  // case of CHECK-EMPTY but not CHECK-NEXT.
-  size_t MatchStartSkip = CheckTy == Check::CheckEmpty;
-  MatchLen = FullMatch.size() - MatchStartSkip;
-  return FullMatch.data() - Buffer.data() + MatchStartSkip;
-}
-
-unsigned FileCheckPattern::computeMatchDistance(StringRef Buffer) const {
-  // Just compute the number of matching characters. For regular expressions, we
-  // just compare against the regex itself and hope for the best.
-  //
-  // FIXME: One easy improvement here is have the regex lib generate a single
-  // example regular expression which matches, and use that as the example
-  // string.
-  StringRef ExampleString(FixedStr);
-  if (ExampleString.empty())
-    ExampleString = RegExStr;
-
-  // Only compare up to the first line in the buffer, or the string size.
-  StringRef BufferPrefix = Buffer.substr(0, ExampleString.size());
-  BufferPrefix = BufferPrefix.split('\n').first;
-  return BufferPrefix.edit_distance(ExampleString);
-}
-
-void FileCheckPattern::printSubstitutions(const SourceMgr &SM, StringRef Buffer,
-                                          SMRange MatchRange) const {
-  // Print what we know about substitutions.
-  if (!Substitutions.empty()) {
-    for (const auto &Substitution : Substitutions) {
-      SmallString<256> Msg;
-      raw_svector_ostream OS(Msg);
-      Expected<std::string> MatchedValue = Substitution->getResult();
-
-      // Substitution failed or is not known at match time, print the undefined
-      // variables it uses.
-      if (!MatchedValue) {
-        bool UndefSeen = false;
-        handleAllErrors(MatchedValue.takeError(),
-                        [](const FileCheckNotFoundError &E) {},
-                        // Handled in PrintNoMatch().
-                        [](const FileCheckErrorDiagnostic &E) {},
-                        [&](const FileCheckUndefVarError &E) {
-                          if (!UndefSeen) {
-                            OS << "uses undefined variable(s):";
-                            UndefSeen = true;
-                          }
-                          OS << " ";
-                          E.log(OS);
-                        });
-      } else {
-        // Substitution succeeded. Print substituted value.
-        OS << "with \"";
-        OS.write_escaped(Substitution->getFromString()) << "\" equal to \"";
-        OS.write_escaped(*MatchedValue) << "\"";
-      }
-
-      if (MatchRange.isValid())
-        SM.PrintMessage(MatchRange.Start, SourceMgr::DK_Note, OS.str(),
-                        {MatchRange});
-      else
-        SM.PrintMessage(SMLoc::getFromPointer(Buffer.data()),
-                        SourceMgr::DK_Note, OS.str());
-    }
-  }
-}
-
-static SMRange ProcessMatchResult(FileCheckDiag::MatchType MatchTy,
-                                  const SourceMgr &SM, SMLoc Loc,
-                                  Check::FileCheckType CheckTy,
-                                  StringRef Buffer, size_t Pos, size_t Len,
-                                  std::vector<FileCheckDiag> *Diags,
-                                  bool AdjustPrevDiag = false) {
-  SMLoc Start = SMLoc::getFromPointer(Buffer.data() + Pos);
-  SMLoc End = SMLoc::getFromPointer(Buffer.data() + Pos + Len);
-  SMRange Range(Start, End);
-  if (Diags) {
-    if (AdjustPrevDiag)
-      Diags->rbegin()->MatchTy = MatchTy;
-    else
-      Diags->emplace_back(SM, CheckTy, Loc, MatchTy, Range);
-  }
-  return Range;
-}
-
-void FileCheckPattern::printFuzzyMatch(
-    const SourceMgr &SM, StringRef Buffer,
-    std::vector<FileCheckDiag> *Diags) const {
-  // Attempt to find the closest/best fuzzy match.  Usually an error happens
-  // because some string in the output didn't exactly match. In these cases, we
-  // would like to show the user a best guess at what "should have" matched, to
-  // save them having to actually check the input manually.
-  size_t NumLinesForward = 0;
-  size_t Best = StringRef::npos;
-  double BestQuality = 0;
-
-  // Use an arbitrary 4k limit on how far we will search.
-  for (size_t i = 0, e = std::min(size_t(4096), Buffer.size()); i != e; ++i) {
-    if (Buffer[i] == '\n')
-      ++NumLinesForward;
-
-    // Patterns have leading whitespace stripped, so skip whitespace when
-    // looking for something which looks like a pattern.
-    if (Buffer[i] == ' ' || Buffer[i] == '\t')
-      continue;
-
-    // Compute the "quality" of this match as an arbitrary combination of the
-    // match distance and the number of lines skipped to get to this match.
-    unsigned Distance = computeMatchDistance(Buffer.substr(i));
-    double Quality = Distance + (NumLinesForward / 100.);
-
-    if (Quality < BestQuality || Best == StringRef::npos) {
-      Best = i;
-      BestQuality = Quality;
-    }
-  }
-
-  // Print the "possible intended match here" line if we found something
-  // reasonable and not equal to what we showed in the "scanning from here"
-  // line.
-  if (Best && Best != StringRef::npos && BestQuality < 50) {
-    SMRange MatchRange =
-        ProcessMatchResult(FileCheckDiag::MatchFuzzy, SM, getLoc(),
-                           getCheckTy(), Buffer, Best, 0, Diags);
-    SM.PrintMessage(MatchRange.Start, SourceMgr::DK_Note,
-                    "possible intended match here");
-
-    // FIXME: If we wanted to be really friendly we would show why the match
-    // failed, as it can be hard to spot simple one character differences.
-  }
-}
-
-Expected<StringRef>
-FileCheckPatternContext::getPatternVarValue(StringRef VarName) {
-  auto VarIter = GlobalVariableTable.find(VarName);
-  if (VarIter == GlobalVariableTable.end())
-    return make_error<FileCheckUndefVarError>(VarName);
-
-  return VarIter->second;
-}
-
-template <class... Types>
-FileCheckNumericVariable *
-FileCheckPatternContext::makeNumericVariable(Types... args) {
-  NumericVariables.push_back(
-      std::make_unique<FileCheckNumericVariable>(args...));
-  return NumericVariables.back().get();
-}
-
-FileCheckSubstitution *
-FileCheckPatternContext::makeStringSubstitution(StringRef VarName,
-                                                size_t InsertIdx) {
-  Substitutions.push_back(
-      std::make_unique<FileCheckStringSubstitution>(this, VarName, InsertIdx));
-  return Substitutions.back().get();
-}
-
-FileCheckSubstitution *FileCheckPatternContext::makeNumericSubstitution(
-    StringRef ExpressionStr,
-    std::unique_ptr<FileCheckExpressionAST> ExpressionAST, size_t InsertIdx) {
-  Substitutions.push_back(std::make_unique<FileCheckNumericSubstitution>(
-      this, ExpressionStr, std::move(ExpressionAST), InsertIdx));
-  return Substitutions.back().get();
-}
-
-size_t FileCheckPattern::FindRegexVarEnd(StringRef Str, SourceMgr &SM) {
-  // Offset keeps track of the current offset within the input Str
-  size_t Offset = 0;
-  // [...] Nesting depth
-  size_t BracketDepth = 0;
-
-  while (!Str.empty()) {
-    if (Str.startswith("]]") && BracketDepth == 0)
-      return Offset;
-    if (Str[0] == '\\') {
-      // Backslash escapes the next char within regexes, so skip them both.
-      Str = Str.substr(2);
-      Offset += 2;
-    } else {
-      switch (Str[0]) {
-      default:
-        break;
-      case '[':
-        BracketDepth++;
-        break;
-      case ']':
-        if (BracketDepth == 0) {
-          SM.PrintMessage(SMLoc::getFromPointer(Str.data()),
-                          SourceMgr::DK_Error,
-                          "missing closing \"]\" for regex variable");
-          exit(1);
-        }
-        BracketDepth--;
-        break;
-      }
-      Str = Str.substr(1);
-      Offset++;
-    }
-  }
-
-  return StringRef::npos;
-}
-
-StringRef FileCheck::CanonicalizeFile(MemoryBuffer &MB,
-                                      SmallVectorImpl<char> &OutputBuffer) {
-  OutputBuffer.reserve(MB.getBufferSize());
-
-  for (const char *Ptr = MB.getBufferStart(), *End = MB.getBufferEnd();
-       Ptr != End; ++Ptr) {
-    // Eliminate trailing dosish \r.
-    if (Ptr <= End - 2 && Ptr[0] == '\r' && Ptr[1] == '\n') {
-      continue;
-    }
-
-    // If current char is not a horizontal whitespace or if horizontal
-    // whitespace canonicalization is disabled, dump it to output as is.
-    if (Req.NoCanonicalizeWhiteSpace || (*Ptr != ' ' && *Ptr != '\t')) {
-      OutputBuffer.push_back(*Ptr);
-      continue;
-    }
-
-    // Otherwise, add one space and advance over neighboring space.
-    OutputBuffer.push_back(' ');
-    while (Ptr + 1 != End && (Ptr[1] == ' ' || Ptr[1] == '\t'))
-      ++Ptr;
-  }
-
-  // Add a null byte and then return all but that byte.
-  OutputBuffer.push_back('\0');
-  return StringRef(OutputBuffer.data(), OutputBuffer.size() - 1);
-}
-
-FileCheckDiag::FileCheckDiag(const SourceMgr &SM,
-                             const Check::FileCheckType &CheckTy,
-                             SMLoc CheckLoc, MatchType MatchTy,
-                             SMRange InputRange)
-    : CheckTy(CheckTy), MatchTy(MatchTy) {
-  auto Start = SM.getLineAndColumn(InputRange.Start);
-  auto End = SM.getLineAndColumn(InputRange.End);
-  InputStartLine = Start.first;
-  InputStartCol = Start.second;
-  InputEndLine = End.first;
-  InputEndCol = End.second;
-  Start = SM.getLineAndColumn(CheckLoc);
-  CheckLine = Start.first;
-  CheckCol = Start.second;
-}
-
-static bool IsPartOfWord(char c) {
-  return (isalnum(c) || c == '-' || c == '_');
-}
-
-Check::FileCheckType &Check::FileCheckType::setCount(int C) {
-  assert(Count > 0 && "zero and negative counts are not supported");
-  assert((C == 1 || Kind == CheckPlain) &&
-         "count supported only for plain CHECK directives");
-  Count = C;
-  return *this;
-}
-
-std::string Check::FileCheckType::getDescription(StringRef Prefix) const {
-  switch (Kind) {
-  case Check::CheckNone:
-    return "invalid";
-  case Check::CheckPlain:
-    if (Count > 1)
-      return Prefix.str() + "-COUNT";
-    return Prefix;
-  case Check::CheckNext:
-    return Prefix.str() + "-NEXT";
-  case Check::CheckSame:
-    return Prefix.str() + "-SAME";
-  case Check::CheckNot:
-    return Prefix.str() + "-NOT";
-  case Check::CheckDAG:
-    return Prefix.str() + "-DAG";
-  case Check::CheckLabel:
-    return Prefix.str() + "-LABEL";
-  case Check::CheckEmpty:
-    return Prefix.str() + "-EMPTY";
-  case Check::CheckEOF:
-    return "implicit EOF";
-  case Check::CheckBadNot:
-    return "bad NOT";
-  case Check::CheckBadCount:
-    return "bad COUNT";
-  }
-  llvm_unreachable("unknown FileCheckType");
-}
-
-static std::pair<Check::FileCheckType, StringRef>
-FindCheckType(StringRef Buffer, StringRef Prefix) {
-  if (Buffer.size() <= Prefix.size())
-    return {Check::CheckNone, StringRef()};
-
-  char NextChar = Buffer[Prefix.size()];
-
-  StringRef Rest = Buffer.drop_front(Prefix.size() + 1);
-  // Verify that the : is present after the prefix.
-  if (NextChar == ':')
-    return {Check::CheckPlain, Rest};
-
-  if (NextChar != '-')
-    return {Check::CheckNone, StringRef()};
-
-  if (Rest.consume_front("COUNT-")) {
-    int64_t Count;
-    if (Rest.consumeInteger(10, Count))
-      // Error happened in parsing integer.
-      return {Check::CheckBadCount, Rest};
-    if (Count <= 0 || Count > INT32_MAX)
-      return {Check::CheckBadCount, Rest};
-    if (!Rest.consume_front(":"))
-      return {Check::CheckBadCount, Rest};
-    return {Check::FileCheckType(Check::CheckPlain).setCount(Count), Rest};
-  }
-
-  if (Rest.consume_front("NEXT:"))
-    return {Check::CheckNext, Rest};
-
-  if (Rest.consume_front("SAME:"))
-    return {Check::CheckSame, Rest};
-
-  if (Rest.consume_front("NOT:"))
-    return {Check::CheckNot, Rest};
-
-  if (Rest.consume_front("DAG:"))
-    return {Check::CheckDAG, Rest};
-
-  if (Rest.consume_front("LABEL:"))
-    return {Check::CheckLabel, Rest};
-
-  if (Rest.consume_front("EMPTY:"))
-    return {Check::CheckEmpty, Rest};
-
-  // You can't combine -NOT with another suffix.
-  if (Rest.startswith("DAG-NOT:") || Rest.startswith("NOT-DAG:") ||
-      Rest.startswith("NEXT-NOT:") || Rest.startswith("NOT-NEXT:") ||
-      Rest.startswith("SAME-NOT:") || Rest.startswith("NOT-SAME:") ||
-      Rest.startswith("EMPTY-NOT:") || Rest.startswith("NOT-EMPTY:"))
-    return {Check::CheckBadNot, Rest};
-
-  return {Check::CheckNone, Rest};
-}
-
-// From the given position, find the next character after the word.
-static size_t SkipWord(StringRef Str, size_t Loc) {
-  while (Loc < Str.size() && IsPartOfWord(Str[Loc]))
-    ++Loc;
-  return Loc;
-}
-
-/// Searches the buffer for the first prefix in the prefix regular expression.
-///
-/// This searches the buffer using the provided regular expression, however it
-/// enforces constraints beyond that:
-/// 1) The found prefix must not be a suffix of something that looks like
-///    a valid prefix.
-/// 2) The found prefix must be followed by a valid check type suffix using \c
-///    FindCheckType above.
-///
-/// \returns a pair of StringRefs into the Buffer, which combines:
-///   - the first match of the regular expression to satisfy these two is
-///   returned,
-///     otherwise an empty StringRef is returned to indicate failure.
-///   - buffer rewound to the location right after parsed suffix, for parsing
-///     to continue from
-///
-/// If this routine returns a valid prefix, it will also shrink \p Buffer to
-/// start at the beginning of the returned prefix, increment \p LineNumber for
-/// each new line consumed from \p Buffer, and set \p CheckTy to the type of
-/// check found by examining the suffix.
-///
-/// If no valid prefix is found, the state of Buffer, LineNumber, and CheckTy
-/// is unspecified.
-static std::pair<StringRef, StringRef>
-FindFirstMatchingPrefix(Regex &PrefixRE, StringRef &Buffer,
-                        unsigned &LineNumber, Check::FileCheckType &CheckTy) {
-  SmallVector<StringRef, 2> Matches;
-
-  while (!Buffer.empty()) {
-    // Find the first (longest) match using the RE.
-    if (!PrefixRE.match(Buffer, &Matches))
-      // No match at all, bail.
-      return {StringRef(), StringRef()};
-
-    StringRef Prefix = Matches[0];
-    Matches.clear();
-
-    assert(Prefix.data() >= Buffer.data() &&
-           Prefix.data() < Buffer.data() + Buffer.size() &&
-           "Prefix doesn't start inside of buffer!");
-    size_t Loc = Prefix.data() - Buffer.data();
-    StringRef Skipped = Buffer.substr(0, Loc);
-    Buffer = Buffer.drop_front(Loc);
-    LineNumber += Skipped.count('\n');
-
-    // Check that the matched prefix isn't a suffix of some other check-like
-    // word.
-    // FIXME: This is a very ad-hoc check. it would be better handled in some
-    // other way. Among other things it seems hard to distinguish between
-    // intentional and unintentional uses of this feature.
-    if (Skipped.empty() || !IsPartOfWord(Skipped.back())) {
-      // Now extract the type.
-      StringRef AfterSuffix;
-      std::tie(CheckTy, AfterSuffix) = FindCheckType(Buffer, Prefix);
-
-      // If we've found a valid check type for this prefix, we're done.
-      if (CheckTy != Check::CheckNone)
-        return {Prefix, AfterSuffix};
-    }
-
-    // If we didn't successfully find a prefix, we need to skip this invalid
-    // prefix and continue scanning. We directly skip the prefix that was
-    // matched and any additional parts of that check-like word.
-    Buffer = Buffer.drop_front(SkipWord(Buffer, Prefix.size()));
-  }
-
-  // We ran out of buffer while skipping partial matches so give up.
-  return {StringRef(), StringRef()};
-}
-
-void FileCheckPatternContext::createLineVariable() {
-  assert(!LineVariable && "@LINE pseudo numeric variable already created");
-  StringRef LineName = "@LINE";
-  LineVariable = makeNumericVariable(LineName);
-  GlobalNumericVariableTable[LineName] = LineVariable;
-}
-
-FileCheck::FileCheck(FileCheckRequest Req)
-    : Req(Req), PatternContext(std::make_unique<FileCheckPatternContext>()),
-      CheckStrings(std::make_unique<std::vector<FileCheckString>>()) {}
-
-FileCheck::~FileCheck() = default;
-
-bool FileCheck::readCheckFile(SourceMgr &SM, StringRef Buffer,
-                              Regex &PrefixRE) {
-  Error DefineError =
-      PatternContext->defineCmdlineVariables(Req.GlobalDefines, SM);
-  if (DefineError) {
-    logAllUnhandledErrors(std::move(DefineError), errs());
-    return true;
-  }
-
-  PatternContext->createLineVariable();
-
-  std::vector<FileCheckPattern> ImplicitNegativeChecks;
-  for (const auto &PatternString : Req.ImplicitCheckNot) {
-    // Create a buffer with fake command line content in order to display the
-    // command line option responsible for the specific implicit CHECK-NOT.
-    std::string Prefix = "-implicit-check-not='";
-    std::string Suffix = "'";
-    std::unique_ptr<MemoryBuffer> CmdLine = MemoryBuffer::getMemBufferCopy(
-        Prefix + PatternString + Suffix, "command line");
-
-    StringRef PatternInBuffer =
-        CmdLine->getBuffer().substr(Prefix.size(), PatternString.size());
-    SM.AddNewSourceBuffer(std::move(CmdLine), SMLoc());
-
-    ImplicitNegativeChecks.push_back(
-        FileCheckPattern(Check::CheckNot, PatternContext.get()));
-    ImplicitNegativeChecks.back().parsePattern(PatternInBuffer,
-                                               "IMPLICIT-CHECK", SM, Req);
-  }
-
-  std::vector<FileCheckPattern> DagNotMatches = ImplicitNegativeChecks;
-
-  // LineNumber keeps track of the line on which CheckPrefix instances are
-  // found.
-  unsigned LineNumber = 1;
-
-  while (1) {
-    Check::FileCheckType CheckTy;
-
-    // See if a prefix occurs in the memory buffer.
-    StringRef UsedPrefix;
-    StringRef AfterSuffix;
-    std::tie(UsedPrefix, AfterSuffix) =
-        FindFirstMatchingPrefix(PrefixRE, Buffer, LineNumber, CheckTy);
-    if (UsedPrefix.empty())
-      break;
-    assert(UsedPrefix.data() == Buffer.data() &&
-           "Failed to move Buffer's start forward, or pointed prefix outside "
-           "of the buffer!");
-    assert(AfterSuffix.data() >= Buffer.data() &&
-           AfterSuffix.data() < Buffer.data() + Buffer.size() &&
-           "Parsing after suffix doesn't start inside of buffer!");
-
-    // Location to use for error messages.
-    const char *UsedPrefixStart = UsedPrefix.data();
-
-    // Skip the buffer to the end of parsed suffix (or just prefix, if no good
-    // suffix was processed).
-    Buffer = AfterSuffix.empty() ? Buffer.drop_front(UsedPrefix.size())
-                                 : AfterSuffix;
-
-    // Complain about useful-looking but unsupported suffixes.
-    if (CheckTy == Check::CheckBadNot) {
-      SM.PrintMessage(SMLoc::getFromPointer(Buffer.data()), SourceMgr::DK_Error,
-                      "unsupported -NOT combo on prefix '" + UsedPrefix + "'");
-      return true;
-    }
-
-    // Complain about invalid count specification.
-    if (CheckTy == Check::CheckBadCount) {
-      SM.PrintMessage(SMLoc::getFromPointer(Buffer.data()), SourceMgr::DK_Error,
-                      "invalid count in -COUNT specification on prefix '" +
-                          UsedPrefix + "'");
-      return true;
-    }
-
-    // Okay, we found the prefix, yay. Remember the rest of the line, but ignore
-    // leading whitespace.
-    if (!(Req.NoCanonicalizeWhiteSpace && Req.MatchFullLines))
-      Buffer = Buffer.substr(Buffer.find_first_not_of(" \t"));
-
-    // Scan ahead to the end of line.
-    size_t EOL = Buffer.find_first_of("\n\r");
-
-    // Remember the location of the start of the pattern, for diagnostics.
-    SMLoc PatternLoc = SMLoc::getFromPointer(Buffer.data());
-
-    // Parse the pattern.
-    FileCheckPattern P(CheckTy, PatternContext.get(), LineNumber);
-    if (P.parsePattern(Buffer.substr(0, EOL), UsedPrefix, SM, Req))
-      return true;
-
-    // Verify that CHECK-LABEL lines do not define or use variables
-    if ((CheckTy == Check::CheckLabel) && P.hasVariable()) {
-      SM.PrintMessage(
-          SMLoc::getFromPointer(UsedPrefixStart), SourceMgr::DK_Error,
-          "found '" + UsedPrefix + "-LABEL:'"
-                                   " with variable definition or use");
-      return true;
-    }
-
-    Buffer = Buffer.substr(EOL);
-
-    // Verify that CHECK-NEXT/SAME/EMPTY lines have at least one CHECK line before them.
-    if ((CheckTy == Check::CheckNext || CheckTy == Check::CheckSame ||
-         CheckTy == Check::CheckEmpty) &&
-        CheckStrings->empty()) {
-      StringRef Type = CheckTy == Check::CheckNext
-                           ? "NEXT"
-                           : CheckTy == Check::CheckEmpty ? "EMPTY" : "SAME";
-      SM.PrintMessage(SMLoc::getFromPointer(UsedPrefixStart),
-                      SourceMgr::DK_Error,
-                      "found '" + UsedPrefix + "-" + Type +
-                          "' without previous '" + UsedPrefix + ": line");
-      return true;
-    }
-
-    // Handle CHECK-DAG/-NOT.
-    if (CheckTy == Check::CheckDAG || CheckTy == Check::CheckNot) {
-      DagNotMatches.push_back(P);
-      continue;
-    }
-
-    // Okay, add the string we captured to the output vector and move on.
-    CheckStrings->emplace_back(P, UsedPrefix, PatternLoc);
-    std::swap(DagNotMatches, CheckStrings->back().DagNotStrings);
-    DagNotMatches = ImplicitNegativeChecks;
-  }
-
-  // Add an EOF pattern for any trailing CHECK-DAG/-NOTs, and use the first
-  // prefix as a filler for the error message.
-  if (!DagNotMatches.empty()) {
-    CheckStrings->emplace_back(
-        FileCheckPattern(Check::CheckEOF, PatternContext.get(), LineNumber + 1),
-        *Req.CheckPrefixes.begin(), SMLoc::getFromPointer(Buffer.data()));
-    std::swap(DagNotMatches, CheckStrings->back().DagNotStrings);
-  }
-
-  if (CheckStrings->empty()) {
-    errs() << "error: no check strings found with prefix"
-           << (Req.CheckPrefixes.size() > 1 ? "es " : " ");
-    auto I = Req.CheckPrefixes.begin();
-    auto E = Req.CheckPrefixes.end();
-    if (I != E) {
-      errs() << "\'" << *I << ":'";
-      ++I;
-    }
-    for (; I != E; ++I)
-      errs() << ", \'" << *I << ":'";
-
-    errs() << '\n';
-    return true;
-  }
-
-  return false;
-}
-
-static void PrintMatch(bool ExpectedMatch, const SourceMgr &SM,
-                       StringRef Prefix, SMLoc Loc, const FileCheckPattern &Pat,
-                       int MatchedCount, StringRef Buffer, size_t MatchPos,
-                       size_t MatchLen, const FileCheckRequest &Req,
-                       std::vector<FileCheckDiag> *Diags) {
-  bool PrintDiag = true;
-  if (ExpectedMatch) {
-    if (!Req.Verbose)
-      return;
-    if (!Req.VerboseVerbose && Pat.getCheckTy() == Check::CheckEOF)
-      return;
-    // Due to their verbosity, we don't print verbose diagnostics here if we're
-    // gathering them for a different rendering, but we always print other
-    // diagnostics.
-    PrintDiag = !Diags;
-  }
-  SMRange MatchRange = ProcessMatchResult(
-      ExpectedMatch ? FileCheckDiag::MatchFoundAndExpected
-                    : FileCheckDiag::MatchFoundButExcluded,
-      SM, Loc, Pat.getCheckTy(), Buffer, MatchPos, MatchLen, Diags);
-  if (!PrintDiag)
-    return;
-
-  std::string Message = formatv("{0}: {1} string found in input",
-                                Pat.getCheckTy().getDescription(Prefix),
-                                (ExpectedMatch ? "expected" : "excluded"))
-                            .str();
-  if (Pat.getCount() > 1)
-    Message += formatv(" ({0} out of {1})", MatchedCount, Pat.getCount()).str();
-
-  SM.PrintMessage(
-      Loc, ExpectedMatch ? SourceMgr::DK_Remark : SourceMgr::DK_Error, Message);
-  SM.PrintMessage(MatchRange.Start, SourceMgr::DK_Note, "found here",
-                  {MatchRange});
-  Pat.printSubstitutions(SM, Buffer, MatchRange);
-}
-
-static void PrintMatch(bool ExpectedMatch, const SourceMgr &SM,
-                       const FileCheckString &CheckStr, int MatchedCount,
-                       StringRef Buffer, size_t MatchPos, size_t MatchLen,
-                       FileCheckRequest &Req,
-                       std::vector<FileCheckDiag> *Diags) {
-  PrintMatch(ExpectedMatch, SM, CheckStr.Prefix, CheckStr.Loc, CheckStr.Pat,
-             MatchedCount, Buffer, MatchPos, MatchLen, Req, Diags);
-}
-
-static void PrintNoMatch(bool ExpectedMatch, const SourceMgr &SM,
-                         StringRef Prefix, SMLoc Loc,
-                         const FileCheckPattern &Pat, int MatchedCount,
-                         StringRef Buffer, bool VerboseVerbose,
-                         std::vector<FileCheckDiag> *Diags, Error MatchErrors) {
-  assert(MatchErrors && "Called on successful match");
-  bool PrintDiag = true;
-  if (!ExpectedMatch) {
-    if (!VerboseVerbose) {
-      consumeError(std::move(MatchErrors));
-      return;
-    }
-    // Due to their verbosity, we don't print verbose diagnostics here if we're
-    // gathering them for a different rendering, but we always print other
-    // diagnostics.
-    PrintDiag = !Diags;
-  }
-
-  // If the current position is at the end of a line, advance to the start of
-  // the next line.
-  Buffer = Buffer.substr(Buffer.find_first_not_of(" \t\n\r"));
-  SMRange SearchRange = ProcessMatchResult(
-      ExpectedMatch ? FileCheckDiag::MatchNoneButExpected
-                    : FileCheckDiag::MatchNoneAndExcluded,
-      SM, Loc, Pat.getCheckTy(), Buffer, 0, Buffer.size(), Diags);
-  if (!PrintDiag) {
-    consumeError(std::move(MatchErrors));
-    return;
-  }
-
-  MatchErrors =
-      handleErrors(std::move(MatchErrors),
-                   [](const FileCheckErrorDiagnostic &E) { E.log(errs()); });
-
-  // No problem matching the string per se.
-  if (!MatchErrors)
-    return;
-  consumeError(std::move(MatchErrors));
-
-  // Print "not found" diagnostic.
-  std::string Message = formatv("{0}: {1} string not found in input",
-                                Pat.getCheckTy().getDescription(Prefix),
-                                (ExpectedMatch ? "expected" : "excluded"))
-                            .str();
-  if (Pat.getCount() > 1)
-    Message += formatv(" ({0} out of {1})", MatchedCount, Pat.getCount()).str();
-  SM.PrintMessage(
-      Loc, ExpectedMatch ? SourceMgr::DK_Error : SourceMgr::DK_Remark, Message);
-
-  // Print the "scanning from here" line.
-  SM.PrintMessage(SearchRange.Start, SourceMgr::DK_Note, "scanning from here");
-
-  // Allow the pattern to print additional information if desired.
-  Pat.printSubstitutions(SM, Buffer);
-
-  if (ExpectedMatch)
-    Pat.printFuzzyMatch(SM, Buffer, Diags);
-}
-
-static void PrintNoMatch(bool ExpectedMatch, const SourceMgr &SM,
-                         const FileCheckString &CheckStr, int MatchedCount,
-                         StringRef Buffer, bool VerboseVerbose,
-                         std::vector<FileCheckDiag> *Diags, Error MatchErrors) {
-  PrintNoMatch(ExpectedMatch, SM, CheckStr.Prefix, CheckStr.Loc, CheckStr.Pat,
-               MatchedCount, Buffer, VerboseVerbose, Diags,
-               std::move(MatchErrors));
-}
-
-/// Counts the number of newlines in the specified range.
-static unsigned CountNumNewlinesBetween(StringRef Range,
-                                        const char *&FirstNewLine) {
-  unsigned NumNewLines = 0;
-  while (1) {
-    // Scan for newline.
-    Range = Range.substr(Range.find_first_of("\n\r"));
-    if (Range.empty())
-      return NumNewLines;
-
-    ++NumNewLines;
-
-    // Handle \n\r and \r\n as a single newline.
-    if (Range.size() > 1 && (Range[1] == '\n' || Range[1] == '\r') &&
-        (Range[0] != Range[1]))
-      Range = Range.substr(1);
-    Range = Range.substr(1);
-
-    if (NumNewLines == 1)
-      FirstNewLine = Range.begin();
-  }
-}
-
-size_t FileCheckString::Check(const SourceMgr &SM, StringRef Buffer,
-                              bool IsLabelScanMode, size_t &MatchLen,
-                              FileCheckRequest &Req,
-                              std::vector<FileCheckDiag> *Diags) const {
-  size_t LastPos = 0;
-  std::vector<const FileCheckPattern *> NotStrings;
-
-  // IsLabelScanMode is true when we are scanning forward to find CHECK-LABEL
-  // bounds; we have not processed variable definitions within the bounded block
-  // yet so cannot handle any final CHECK-DAG yet; this is handled when going
-  // over the block again (including the last CHECK-LABEL) in normal mode.
-  if (!IsLabelScanMode) {
-    // Match "dag strings" (with mixed "not strings" if any).
-    LastPos = CheckDag(SM, Buffer, NotStrings, Req, Diags);
-    if (LastPos == StringRef::npos)
-      return StringRef::npos;
-  }
-
-  // Match itself from the last position after matching CHECK-DAG.
-  size_t LastMatchEnd = LastPos;
-  size_t FirstMatchPos = 0;
-  // Go match the pattern Count times. Majority of patterns only match with
-  // count 1 though.
-  assert(Pat.getCount() != 0 && "pattern count can not be zero");
-  for (int i = 1; i <= Pat.getCount(); i++) {
-    StringRef MatchBuffer = Buffer.substr(LastMatchEnd);
-    size_t CurrentMatchLen;
-    // get a match at current start point
-    Expected<size_t> MatchResult = Pat.match(MatchBuffer, CurrentMatchLen, SM);
-
-    // report
-    if (!MatchResult) {
-      PrintNoMatch(true, SM, *this, i, MatchBuffer, Req.VerboseVerbose, Diags,
-                   MatchResult.takeError());
-      return StringRef::npos;
-    }
-    size_t MatchPos = *MatchResult;
-    PrintMatch(true, SM, *this, i, MatchBuffer, MatchPos, CurrentMatchLen, Req,
-               Diags);
-    if (i == 1)
-      FirstMatchPos = LastPos + MatchPos;
-
-    // move start point after the match
-    LastMatchEnd += MatchPos + CurrentMatchLen;
-  }
-  // Full match len counts from first match pos.
-  MatchLen = LastMatchEnd - FirstMatchPos;
-
-  // Similar to the above, in "label-scan mode" we can't yet handle CHECK-NEXT
-  // or CHECK-NOT
-  if (!IsLabelScanMode) {
-    size_t MatchPos = FirstMatchPos - LastPos;
-    StringRef MatchBuffer = Buffer.substr(LastPos);
-    StringRef SkippedRegion = Buffer.substr(LastPos, MatchPos);
-
-    // If this check is a "CHECK-NEXT", verify that the previous match was on
-    // the previous line (i.e. that there is one newline between them).
-    if (CheckNext(SM, SkippedRegion)) {
-      ProcessMatchResult(FileCheckDiag::MatchFoundButWrongLine, SM, Loc,
-                         Pat.getCheckTy(), MatchBuffer, MatchPos, MatchLen,
-                         Diags, Req.Verbose);
-      return StringRef::npos;
-    }
-
-    // If this check is a "CHECK-SAME", verify that the previous match was on
-    // the same line (i.e. that there is no newline between them).
-    if (CheckSame(SM, SkippedRegion)) {
-      ProcessMatchResult(FileCheckDiag::MatchFoundButWrongLine, SM, Loc,
-                         Pat.getCheckTy(), MatchBuffer, MatchPos, MatchLen,
-                         Diags, Req.Verbose);
-      return StringRef::npos;
-    }
-
-    // If this match had "not strings", verify that they don't exist in the
-    // skipped region.
-    if (CheckNot(SM, SkippedRegion, NotStrings, Req, Diags))
-      return StringRef::npos;
-  }
-
-  return FirstMatchPos;
-}
-
-bool FileCheckString::CheckNext(const SourceMgr &SM, StringRef Buffer) const {
-  if (Pat.getCheckTy() != Check::CheckNext &&
-      Pat.getCheckTy() != Check::CheckEmpty)
-    return false;
-
-  Twine CheckName =
-      Prefix +
-      Twine(Pat.getCheckTy() == Check::CheckEmpty ? "-EMPTY" : "-NEXT");
-
-  // Count the number of newlines between the previous match and this one.
-  const char *FirstNewLine = nullptr;
-  unsigned NumNewLines = CountNumNewlinesBetween(Buffer, FirstNewLine);
-
-  if (NumNewLines == 0) {
-    SM.PrintMessage(Loc, SourceMgr::DK_Error,
-                    CheckName + ": is on the same line as previous match");
-    SM.PrintMessage(SMLoc::getFromPointer(Buffer.end()), SourceMgr::DK_Note,
-                    "'next' match was here");
-    SM.PrintMessage(SMLoc::getFromPointer(Buffer.data()), SourceMgr::DK_Note,
-                    "previous match ended here");
-    return true;
-  }
-
-  if (NumNewLines != 1) {
-    SM.PrintMessage(Loc, SourceMgr::DK_Error,
-                    CheckName +
-                        ": is not on the line after the previous match");
-    SM.PrintMessage(SMLoc::getFromPointer(Buffer.end()), SourceMgr::DK_Note,
-                    "'next' match was here");
-    SM.PrintMessage(SMLoc::getFromPointer(Buffer.data()), SourceMgr::DK_Note,
-                    "previous match ended here");
-    SM.PrintMessage(SMLoc::getFromPointer(FirstNewLine), SourceMgr::DK_Note,
-                    "non-matching line after previous match is here");
-    return true;
-  }
-
-  return false;
-}
-
-bool FileCheckString::CheckSame(const SourceMgr &SM, StringRef Buffer) const {
-  if (Pat.getCheckTy() != Check::CheckSame)
-    return false;
-
-  // Count the number of newlines between the previous match and this one.
-  const char *FirstNewLine = nullptr;
-  unsigned NumNewLines = CountNumNewlinesBetween(Buffer, FirstNewLine);
-
-  if (NumNewLines != 0) {
-    SM.PrintMessage(Loc, SourceMgr::DK_Error,
-                    Prefix +
-                        "-SAME: is not on the same line as the previous match");
-    SM.PrintMessage(SMLoc::getFromPointer(Buffer.end()), SourceMgr::DK_Note,
-                    "'next' match was here");
-    SM.PrintMessage(SMLoc::getFromPointer(Buffer.data()), SourceMgr::DK_Note,
-                    "previous match ended here");
-    return true;
-  }
-
-  return false;
-}
-
-bool FileCheckString::CheckNot(
-    const SourceMgr &SM, StringRef Buffer,
-    const std::vector<const FileCheckPattern *> &NotStrings,
-    const FileCheckRequest &Req, std::vector<FileCheckDiag> *Diags) const {
-  for (const FileCheckPattern *Pat : NotStrings) {
-    assert((Pat->getCheckTy() == Check::CheckNot) && "Expect CHECK-NOT!");
-
-    size_t MatchLen = 0;
-    Expected<size_t> MatchResult = Pat->match(Buffer, MatchLen, SM);
-
-    if (!MatchResult) {
-      PrintNoMatch(false, SM, Prefix, Pat->getLoc(), *Pat, 1, Buffer,
-                   Req.VerboseVerbose, Diags, MatchResult.takeError());
-      continue;
-    }
-    size_t Pos = *MatchResult;
-
-    PrintMatch(false, SM, Prefix, Pat->getLoc(), *Pat, 1, Buffer, Pos, MatchLen,
-               Req, Diags);
-
-    return true;
-  }
-
-  return false;
-}
-
-size_t
-FileCheckString::CheckDag(const SourceMgr &SM, StringRef Buffer,
-                          std::vector<const FileCheckPattern *> &NotStrings,
-                          const FileCheckRequest &Req,
-                          std::vector<FileCheckDiag> *Diags) const {
-  if (DagNotStrings.empty())
-    return 0;
-
-  // The start of the search range.
-  size_t StartPos = 0;
-
-  struct MatchRange {
-    size_t Pos;
-    size_t End;
-  };
-  // A sorted list of ranges for non-overlapping CHECK-DAG matches.  Match
-  // ranges are erased from this list once they are no longer in the search
-  // range.
-  std::list<MatchRange> MatchRanges;
-
-  // We need PatItr and PatEnd later for detecting the end of a CHECK-DAG
-  // group, so we don't use a range-based for loop here.
-  for (auto PatItr = DagNotStrings.begin(), PatEnd = DagNotStrings.end();
-       PatItr != PatEnd; ++PatItr) {
-    const FileCheckPattern &Pat = *PatItr;
-    assert((Pat.getCheckTy() == Check::CheckDAG ||
-            Pat.getCheckTy() == Check::CheckNot) &&
-           "Invalid CHECK-DAG or CHECK-NOT!");
-
-    if (Pat.getCheckTy() == Check::CheckNot) {
-      NotStrings.push_back(&Pat);
-      continue;
-    }
-
-    assert((Pat.getCheckTy() == Check::CheckDAG) && "Expect CHECK-DAG!");
-
-    // CHECK-DAG always matches from the start.
-    size_t MatchLen = 0, MatchPos = StartPos;
-
-    // Search for a match that doesn't overlap a previous match in this
-    // CHECK-DAG group.
-    for (auto MI = MatchRanges.begin(), ME = MatchRanges.end(); true; ++MI) {
-      StringRef MatchBuffer = Buffer.substr(MatchPos);
-      Expected<size_t> MatchResult = Pat.match(MatchBuffer, MatchLen, SM);
-      // With a group of CHECK-DAGs, a single mismatching means the match on
-      // that group of CHECK-DAGs fails immediately.
-      if (!MatchResult) {
-        PrintNoMatch(true, SM, Prefix, Pat.getLoc(), Pat, 1, MatchBuffer,
-                     Req.VerboseVerbose, Diags, MatchResult.takeError());
-        return StringRef::npos;
-      }
-      size_t MatchPosBuf = *MatchResult;
-      // Re-calc it as the offset relative to the start of the original string.
-      MatchPos += MatchPosBuf;
-      if (Req.VerboseVerbose)
-        PrintMatch(true, SM, Prefix, Pat.getLoc(), Pat, 1, Buffer, MatchPos,
-                   MatchLen, Req, Diags);
-      MatchRange M{MatchPos, MatchPos + MatchLen};
-      if (Req.AllowDeprecatedDagOverlap) {
-        // We don't need to track all matches in this mode, so we just maintain
-        // one match range that encompasses the current CHECK-DAG group's
-        // matches.
-        if (MatchRanges.empty())
-          MatchRanges.insert(MatchRanges.end(), M);
-        else {
-          auto Block = MatchRanges.begin();
-          Block->Pos = std::min(Block->Pos, M.Pos);
-          Block->End = std::max(Block->End, M.End);
-        }
-        break;
-      }
-      // Iterate previous matches until overlapping match or insertion point.
-      bool Overlap = false;
-      for (; MI != ME; ++MI) {
-        if (M.Pos < MI->End) {
-          // !Overlap => New match has no overlap and is before this old match.
-          // Overlap => New match overlaps this old match.
-          Overlap = MI->Pos < M.End;
-          break;
-        }
-      }
-      if (!Overlap) {
-        // Insert non-overlapping match into list.
-        MatchRanges.insert(MI, M);
-        break;
-      }
-      if (Req.VerboseVerbose) {
-        // Due to their verbosity, we don't print verbose diagnostics here if
-        // we're gathering them for a different rendering, but we always print
-        // other diagnostics.
-        if (!Diags) {
-          SMLoc OldStart = SMLoc::getFromPointer(Buffer.data() + MI->Pos);
-          SMLoc OldEnd = SMLoc::getFromPointer(Buffer.data() + MI->End);
-          SMRange OldRange(OldStart, OldEnd);
-          SM.PrintMessage(OldStart, SourceMgr::DK_Note,
-                          "match discarded, overlaps earlier DAG match here",
-                          {OldRange});
-        } else
-          Diags->rbegin()->MatchTy = FileCheckDiag::MatchFoundButDiscarded;
-      }
-      MatchPos = MI->End;
-    }
-    if (!Req.VerboseVerbose)
-      PrintMatch(true, SM, Prefix, Pat.getLoc(), Pat, 1, Buffer, MatchPos,
-                 MatchLen, Req, Diags);
-
-    // Handle the end of a CHECK-DAG group.
-    if (std::next(PatItr) == PatEnd ||
-        std::next(PatItr)->getCheckTy() == Check::CheckNot) {
-      if (!NotStrings.empty()) {
-        // If there are CHECK-NOTs between two CHECK-DAGs or from CHECK to
-        // CHECK-DAG, verify that there are no 'not' strings occurred in that
-        // region.
-        StringRef SkippedRegion =
-            Buffer.slice(StartPos, MatchRanges.begin()->Pos);
-        if (CheckNot(SM, SkippedRegion, NotStrings, Req, Diags))
-          return StringRef::npos;
-        // Clear "not strings".
-        NotStrings.clear();
-      }
-      // All subsequent CHECK-DAGs and CHECK-NOTs should be matched from the
-      // end of this CHECK-DAG group's match range.
-      StartPos = MatchRanges.rbegin()->End;
-      // Don't waste time checking for (impossible) overlaps before that.
-      MatchRanges.clear();
-    }
-  }
-
-  return StartPos;
-}
-
-// A check prefix must contain only alphanumeric, hyphens and underscores.
-static bool ValidateCheckPrefix(StringRef CheckPrefix) {
-  static const Regex Validator("^[a-zA-Z0-9_-]*$");
-  return Validator.match(CheckPrefix);
-}
-
-bool FileCheck::ValidateCheckPrefixes() {
-  StringSet<> PrefixSet;
-
-  for (StringRef Prefix : Req.CheckPrefixes) {
-    // Reject empty prefixes.
-    if (Prefix == "")
-      return false;
-
-    if (!PrefixSet.insert(Prefix).second)
-      return false;
-
-    if (!ValidateCheckPrefix(Prefix))
-      return false;
-  }
-
-  return true;
-}
-
-Regex FileCheck::buildCheckPrefixRegex() {
-  // I don't think there's a way to specify an initial value for cl::list,
-  // so if nothing was specified, add the default
-  if (Req.CheckPrefixes.empty())
-    Req.CheckPrefixes.push_back("CHECK");
-
-  // We already validated the contents of CheckPrefixes so just concatenate
-  // them as alternatives.
-  SmallString<32> PrefixRegexStr;
-  for (StringRef Prefix : Req.CheckPrefixes) {
-    if (Prefix != Req.CheckPrefixes.front())
-      PrefixRegexStr.push_back('|');
-
-    PrefixRegexStr.append(Prefix);
-  }
-
-  return Regex(PrefixRegexStr);
-}
-
-Error FileCheckPatternContext::defineCmdlineVariables(
-    std::vector<std::string> &CmdlineDefines, SourceMgr &SM) {
-  assert(GlobalVariableTable.empty() && GlobalNumericVariableTable.empty() &&
-         "Overriding defined variable with command-line variable definitions");
-
-  if (CmdlineDefines.empty())
-    return Error::success();
-
-  // Create a string representing the vector of command-line definitions. Each
-  // definition is on its own line and prefixed with a definition number to
-  // clarify which definition a given diagnostic corresponds to.
-  unsigned I = 0;
-  Error Errs = Error::success();
-  std::string CmdlineDefsDiag;
-  SmallVector<std::pair<size_t, size_t>, 4> CmdlineDefsIndices;
-  for (StringRef CmdlineDef : CmdlineDefines) {
-    std::string DefPrefix = ("Global define #" + Twine(++I) + ": ").str();
-    size_t EqIdx = CmdlineDef.find('=');
-    if (EqIdx == StringRef::npos) {
-      CmdlineDefsIndices.push_back(std::make_pair(CmdlineDefsDiag.size(), 0));
-      continue;
-    }
-    // Numeric variable definition.
-    if (CmdlineDef[0] == '#') {
-      // Append a copy of the command-line definition adapted to use the same
-      // format as in the input file to be able to reuse
-      // parseNumericSubstitutionBlock.
-      CmdlineDefsDiag += (DefPrefix + CmdlineDef + " (parsed as: [[").str();
-      std::string SubstitutionStr = CmdlineDef;
-      SubstitutionStr[EqIdx] = ':';
-      CmdlineDefsIndices.push_back(
-          std::make_pair(CmdlineDefsDiag.size(), SubstitutionStr.size()));
-      CmdlineDefsDiag += (SubstitutionStr + Twine("]])\n")).str();
-    } else {
-      CmdlineDefsDiag += DefPrefix;
-      CmdlineDefsIndices.push_back(
-          std::make_pair(CmdlineDefsDiag.size(), CmdlineDef.size()));
-      CmdlineDefsDiag += (CmdlineDef + "\n").str();
-    }
-  }
-
-  // Create a buffer with fake command line content in order to display
-  // parsing diagnostic with location information and point to the
-  // global definition with invalid syntax.
-  std::unique_ptr<MemoryBuffer> CmdLineDefsDiagBuffer =
-      MemoryBuffer::getMemBufferCopy(CmdlineDefsDiag, "Global defines");
-  StringRef CmdlineDefsDiagRef = CmdLineDefsDiagBuffer->getBuffer();
-  SM.AddNewSourceBuffer(std::move(CmdLineDefsDiagBuffer), SMLoc());
-
-  for (std::pair<size_t, size_t> CmdlineDefIndices : CmdlineDefsIndices) {
-    StringRef CmdlineDef = CmdlineDefsDiagRef.substr(CmdlineDefIndices.first,
-                                                     CmdlineDefIndices.second);
-    if (CmdlineDef.empty()) {
-      Errs = joinErrors(
-          std::move(Errs),
-          FileCheckErrorDiagnostic::get(
-              SM, CmdlineDef, "missing equal sign in global definition"));
-      continue;
-    }
-
-    // Numeric variable definition.
-    if (CmdlineDef[0] == '#') {
-      // Now parse the definition both to check that the syntax is correct and
-      // to create the necessary class instance.
-      StringRef CmdlineDefExpr = CmdlineDef.substr(1);
-      Optional<FileCheckNumericVariable *> DefinedNumericVariable;
-      Expected<std::unique_ptr<FileCheckExpressionAST>> ExpressionASTResult =
-          FileCheckPattern::parseNumericSubstitutionBlock(
-              CmdlineDefExpr, DefinedNumericVariable, false, None, this, SM);
-      if (!ExpressionASTResult) {
-        Errs = joinErrors(std::move(Errs), ExpressionASTResult.takeError());
-        continue;
-      }
-      std::unique_ptr<FileCheckExpressionAST> ExpressionAST =
-          std::move(*ExpressionASTResult);
-      // Now evaluate the expression whose value this variable should be set
-      // to, since the expression of a command-line variable definition should
-      // only use variables defined earlier on the command-line. If not, this
-      // is an error and we report it.
-      Expected<uint64_t> Value = ExpressionAST->eval();
-      if (!Value) {
-        Errs = joinErrors(std::move(Errs), Value.takeError());
-        continue;
-      }
-
-      assert(DefinedNumericVariable && "No variable defined");
-      (*DefinedNumericVariable)->setValue(*Value);
-
-      // Record this variable definition.
-      GlobalNumericVariableTable[(*DefinedNumericVariable)->getName()] =
-          *DefinedNumericVariable;
-    } else {
-      // String variable definition.
-      std::pair<StringRef, StringRef> CmdlineNameVal = CmdlineDef.split('=');
-      StringRef CmdlineName = CmdlineNameVal.first;
-      StringRef OrigCmdlineName = CmdlineName;
-      Expected<FileCheckPattern::VariableProperties> ParseVarResult =
-          FileCheckPattern::parseVariable(CmdlineName, SM);
-      if (!ParseVarResult) {
-        Errs = joinErrors(std::move(Errs), ParseVarResult.takeError());
-        continue;
-      }
-      // Check that CmdlineName does not denote a pseudo variable is only
-      // composed of the parsed numeric variable. This catches cases like
-      // "FOO+2" in a "FOO+2=10" definition.
-      if (ParseVarResult->IsPseudo || !CmdlineName.empty()) {
-        Errs = joinErrors(std::move(Errs),
-                          FileCheckErrorDiagnostic::get(
-                              SM, OrigCmdlineName,
-                              "invalid name in string variable definition '" +
-                                  OrigCmdlineName + "'"));
-        continue;
-      }
-      StringRef Name = ParseVarResult->Name;
-
-      // Detect collisions between string and numeric variables when the former
-      // is created later than the latter.
-      if (GlobalNumericVariableTable.find(Name) !=
-          GlobalNumericVariableTable.end()) {
-        Errs = joinErrors(std::move(Errs), FileCheckErrorDiagnostic::get(
-                                               SM, Name,
-                                               "numeric variable with name '" +
-                                                   Name + "' already exists"));
-        continue;
-      }
-      GlobalVariableTable.insert(CmdlineNameVal);
-      // Mark the string variable as defined to detect collisions between
-      // string and numeric variables in defineCmdlineVariables when the latter
-      // is created later than the former. We cannot reuse GlobalVariableTable
-      // for this by populating it with an empty string since we would then
-      // lose the ability to detect the use of an undefined variable in
-      // match().
-      DefinedVariableTable[Name] = true;
-    }
-  }
-
-  return Errs;
-}
-
-void FileCheckPatternContext::clearLocalVars() {
-  SmallVector<StringRef, 16> LocalPatternVars, LocalNumericVars;
-  for (const StringMapEntry<StringRef> &Var : GlobalVariableTable)
-    if (Var.first()[0] != '$')
-      LocalPatternVars.push_back(Var.first());
-
-  // Numeric substitution reads the value of a variable directly, not via
-  // GlobalNumericVariableTable. Therefore, we clear local variables by
-  // clearing their value which will lead to a numeric substitution failure. We
-  // also mark the variable for removal from GlobalNumericVariableTable since
-  // this is what defineCmdlineVariables checks to decide that no global
-  // variable has been defined.
-  for (const auto &Var : GlobalNumericVariableTable)
-    if (Var.first()[0] != '$') {
-      Var.getValue()->clearValue();
-      LocalNumericVars.push_back(Var.first());
-    }
-
-  for (const auto &Var : LocalPatternVars)
-    GlobalVariableTable.erase(Var);
-  for (const auto &Var : LocalNumericVars)
-    GlobalNumericVariableTable.erase(Var);
-}
-
-bool FileCheck::checkInput(SourceMgr &SM, StringRef Buffer,
-                           std::vector<FileCheckDiag> *Diags) {
-  bool ChecksFailed = false;
-
-  unsigned i = 0, j = 0, e = CheckStrings->size();
-  while (true) {
-    StringRef CheckRegion;
-    if (j == e) {
-      CheckRegion = Buffer;
-    } else {
-      const FileCheckString &CheckLabelStr = (*CheckStrings)[j];
-      if (CheckLabelStr.Pat.getCheckTy() != Check::CheckLabel) {
-        ++j;
-        continue;
-      }
-
-      // Scan to next CHECK-LABEL match, ignoring CHECK-NOT and CHECK-DAG
-      size_t MatchLabelLen = 0;
-      size_t MatchLabelPos =
-          CheckLabelStr.Check(SM, Buffer, true, MatchLabelLen, Req, Diags);
-      if (MatchLabelPos == StringRef::npos)
-        // Immediately bail if CHECK-LABEL fails, nothing else we can do.
-        return false;
-
-      CheckRegion = Buffer.substr(0, MatchLabelPos + MatchLabelLen);
-      Buffer = Buffer.substr(MatchLabelPos + MatchLabelLen);
-      ++j;
-    }
-
-    // Do not clear the first region as it's the one before the first
-    // CHECK-LABEL and it would clear variables defined on the command-line
-    // before they get used.
-    if (i != 0 && Req.EnableVarScope)
-      PatternContext->clearLocalVars();
-
-    for (; i != j; ++i) {
-      const FileCheckString &CheckStr = (*CheckStrings)[i];
-
-      // Check each string within the scanned region, including a second check
-      // of any final CHECK-LABEL (to verify CHECK-NOT and CHECK-DAG)
-      size_t MatchLen = 0;
-      size_t MatchPos =
-          CheckStr.Check(SM, CheckRegion, false, MatchLen, Req, Diags);
-
-      if (MatchPos == StringRef::npos) {
-        ChecksFailed = true;
-        i = j;
-        break;
-      }
-
-      CheckRegion = CheckRegion.substr(MatchPos + MatchLen);
-    }
-
-    if (j == e)
-      break;
-  }
-
-  // Success if no checks failed.
-  return !ChecksFailed;
-}
+//===- FileCheck.cpp - Check that File's Contents match what is expected --===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// FileCheck does a line-by line check of a file that validates whether it
+// contains the expected content.  This is useful for regression tests etc.
+//
+// This file implements most of the API that will be used by the FileCheck utility
+// as well as various unittests.
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/FileCheck.h"
+#include "FileCheckImpl.h"
+#include "llvm/ADT/StringSet.h"
+#include "llvm/ADT/Twine.h"
+#include "llvm/Support/FormatVariadic.h"
+#include <cstdint>
+#include <list>
+#include <tuple>
+#include <utility>
+
+using namespace llvm;
+
+Expected<uint64_t> FileCheckNumericVariableUse::eval() const {
+  Optional<uint64_t> Value = NumericVariable->getValue();
+  if (Value)
+    return *Value;
+
+  return make_error<FileCheckUndefVarError>(Name);
+}
+
+Expected<uint64_t> FileCheckASTBinop::eval() const {
+  Expected<uint64_t> LeftOp = LeftOperand->eval();
+  Expected<uint64_t> RightOp = RightOperand->eval();
+
+  // Bubble up any error (e.g. undefined variables) in the recursive
+  // evaluation.
+  if (!LeftOp || !RightOp) {
+    Error Err = Error::success();
+    if (!LeftOp)
+      Err = joinErrors(std::move(Err), LeftOp.takeError());
+    if (!RightOp)
+      Err = joinErrors(std::move(Err), RightOp.takeError());
+    return std::move(Err);
+  }
+
+  return EvalBinop(*LeftOp, *RightOp);
+}
+
+Expected<std::string> FileCheckNumericSubstitution::getResult() const {
+  Expected<uint64_t> EvaluatedValue = ExpressionAST->eval();
+  if (!EvaluatedValue)
+    return EvaluatedValue.takeError();
+  return utostr(*EvaluatedValue);
+}
+
+Expected<std::string> FileCheckStringSubstitution::getResult() const {
+  // Look up the value and escape it so that we can put it into the regex.
+  Expected<StringRef> VarVal = Context->getPatternVarValue(FromStr);
+  if (!VarVal)
+    return VarVal.takeError();
+  return Regex::escape(*VarVal);
+}
+
+bool FileCheckPattern::isValidVarNameStart(char C) {
+  return C == '_' || isalpha(C);
+}
+
+Expected<FileCheckPattern::VariableProperties>
+FileCheckPattern::parseVariable(StringRef &Str, const SourceMgr &SM) {
+  if (Str.empty())
+    return FileCheckErrorDiagnostic::get(SM, Str, "empty variable name");
+
+  bool ParsedOneChar = false;
+  unsigned I = 0;
+  bool IsPseudo = Str[0] == '@';
+
+  // Global vars start with '$'.
+  if (Str[0] == '$' || IsPseudo)
+    ++I;
+
+  for (unsigned E = Str.size(); I != E; ++I) {
+    if (!ParsedOneChar && !isValidVarNameStart(Str[I]))
+      return FileCheckErrorDiagnostic::get(SM, Str, "invalid variable name");
+
+    // Variable names are composed of alphanumeric characters and underscores.
+    if (Str[I] != '_' && !isalnum(Str[I]))
+      break;
+    ParsedOneChar = true;
+  }
+
+  StringRef Name = Str.take_front(I);
+  Str = Str.substr(I);
+  return VariableProperties {Name, IsPseudo};
+}
+
+// StringRef holding all characters considered as horizontal whitespaces by
+// FileCheck input canonicalization.
+constexpr StringLiteral SpaceChars = " \t";
+
+// Parsing helper function that strips the first character in S and returns it.
+static char popFront(StringRef &S) {
+  char C = S.front();
+  S = S.drop_front();
+  return C;
+}
+
+char FileCheckUndefVarError::ID = 0;
+char FileCheckErrorDiagnostic::ID = 0;
+char FileCheckNotFoundError::ID = 0;
+
+Expected<FileCheckNumericVariable *>
+FileCheckPattern::parseNumericVariableDefinition(
+    StringRef &Expr, FileCheckPatternContext *Context,
+    Optional<size_t> LineNumber, const SourceMgr &SM) {
+  Expected<VariableProperties> ParseVarResult = parseVariable(Expr, SM);
+  if (!ParseVarResult)
+    return ParseVarResult.takeError();
+  StringRef Name = ParseVarResult->Name;
+
+  if (ParseVarResult->IsPseudo)
+    return FileCheckErrorDiagnostic::get(
+        SM, Name, "definition of pseudo numeric variable unsupported");
+
+  // Detect collisions between string and numeric variables when the latter
+  // is created later than the former.
+  if (Context->DefinedVariableTable.find(Name) !=
+      Context->DefinedVariableTable.end())
+    return FileCheckErrorDiagnostic::get(
+        SM, Name, "string variable with name '" + Name + "' already exists");
+
+  Expr = Expr.ltrim(SpaceChars);
+  if (!Expr.empty())
+    return FileCheckErrorDiagnostic::get(
+        SM, Expr, "unexpected characters after numeric variable name");
+
+  FileCheckNumericVariable *DefinedNumericVariable;
+  auto VarTableIter = Context->GlobalNumericVariableTable.find(Name);
+  if (VarTableIter != Context->GlobalNumericVariableTable.end())
+    DefinedNumericVariable = VarTableIter->second;
+  else
+    DefinedNumericVariable = Context->makeNumericVariable(Name, LineNumber);
+
+  return DefinedNumericVariable;
+}
+
+Expected<std::unique_ptr<FileCheckNumericVariableUse>>
+FileCheckPattern::parseNumericVariableUse(StringRef Name, bool IsPseudo,
+                                          Optional<size_t> LineNumber,
+                                          FileCheckPatternContext *Context,
+                                          const SourceMgr &SM) {
+  if (IsPseudo && !Name.equals("@LINE"))
+    return FileCheckErrorDiagnostic::get(
+        SM, Name, "invalid pseudo numeric variable '" + Name + "'");
+
+  // Numeric variable definitions and uses are parsed in the order in which
+  // they appear in the CHECK patterns. For each definition, the pointer to the
+  // class instance of the corresponding numeric variable definition is stored
+  // in GlobalNumericVariableTable in parsePattern. Therefore, if the pointer
+  // we get below is null, it means no such variable was defined before. When
+  // that happens, we create a dummy variable so that parsing can continue. All
+  // uses of undefined variables, whether string or numeric, are then diagnosed
+  // in printSubstitutions() after failing to match.
+  auto VarTableIter = Context->GlobalNumericVariableTable.find(Name);
+  FileCheckNumericVariable *NumericVariable;
+  if (VarTableIter != Context->GlobalNumericVariableTable.end())
+    NumericVariable = VarTableIter->second;
+  else {
+    NumericVariable = Context->makeNumericVariable(Name);
+    Context->GlobalNumericVariableTable[Name] = NumericVariable;
+  }
+
+  Optional<size_t> DefLineNumber = NumericVariable->getDefLineNumber();
+  if (DefLineNumber && LineNumber && *DefLineNumber == *LineNumber)
+    return FileCheckErrorDiagnostic::get(
+        SM, Name,
+        "numeric variable '" + Name +
+            "' defined earlier in the same CHECK directive");
+
+  return std::make_unique<FileCheckNumericVariableUse>(Name, NumericVariable);
+}
+
+Expected<std::unique_ptr<FileCheckExpressionAST>>
+FileCheckPattern::parseNumericOperand(StringRef &Expr, AllowedOperand AO,
+                                      Optional<size_t> LineNumber,
+                                      FileCheckPatternContext *Context,
+                                      const SourceMgr &SM) {
+  if (AO == AllowedOperand::LineVar || AO == AllowedOperand::Any) {
+    // Try to parse as a numeric variable use.
+    Expected<FileCheckPattern::VariableProperties> ParseVarResult =
+        parseVariable(Expr, SM);
+    if (ParseVarResult)
+      return parseNumericVariableUse(ParseVarResult->Name,
+                                     ParseVarResult->IsPseudo, LineNumber,
+                                     Context, SM);
+    if (AO == AllowedOperand::LineVar)
+      return ParseVarResult.takeError();
+    // Ignore the error and retry parsing as a literal.
+    consumeError(ParseVarResult.takeError());
+  }
+
+  // Otherwise, parse it as a literal.
+  uint64_t LiteralValue;
+  if (!Expr.consumeInteger(/*Radix=*/10, LiteralValue))
+    return std::make_unique<FileCheckExpressionLiteral>(LiteralValue);
+
+  return FileCheckErrorDiagnostic::get(SM, Expr,
+                                       "invalid operand format '" + Expr + "'");
+}
+
+static uint64_t add(uint64_t LeftOp, uint64_t RightOp) {
+  return LeftOp + RightOp;
+}
+
+static uint64_t sub(uint64_t LeftOp, uint64_t RightOp) {
+  return LeftOp - RightOp;
+}
+
+Expected<std::unique_ptr<FileCheckExpressionAST>> FileCheckPattern::parseBinop(
+    StringRef &Expr, std::unique_ptr<FileCheckExpressionAST> LeftOp,
+    bool IsLegacyLineExpr, Optional<size_t> LineNumber,
+    FileCheckPatternContext *Context, const SourceMgr &SM) {
+  Expr = Expr.ltrim(SpaceChars);
+  if (Expr.empty())
+    return std::move(LeftOp);
+
+  // Check if this is a supported operation and select a function to perform
+  // it.
+  SMLoc OpLoc = SMLoc::getFromPointer(Expr.data());
+  char Operator = popFront(Expr);
+  binop_eval_t EvalBinop;
+  switch (Operator) {
+  case '+':
+    EvalBinop = add;
+    break;
+  case '-':
+    EvalBinop = sub;
+    break;
+  default:
+    return FileCheckErrorDiagnostic::get(
+        SM, OpLoc, Twine("unsupported operation '") + Twine(Operator) + "'");
+  }
+
+  // Parse right operand.
+  Expr = Expr.ltrim(SpaceChars);
+  if (Expr.empty())
+    return FileCheckErrorDiagnostic::get(SM, Expr,
+                                         "missing operand in expression");
+  // The second operand in a legacy @LINE expression is always a literal.
+  AllowedOperand AO =
+      IsLegacyLineExpr ? AllowedOperand::Literal : AllowedOperand::Any;
+  Expected<std::unique_ptr<FileCheckExpressionAST>> RightOpResult =
+      parseNumericOperand(Expr, AO, LineNumber, Context, SM);
+  if (!RightOpResult)
+    return RightOpResult;
+
+  Expr = Expr.ltrim(SpaceChars);
+  return std::make_unique<FileCheckASTBinop>(EvalBinop, std::move(LeftOp),
+                                              std::move(*RightOpResult));
+}
+
+Expected<std::unique_ptr<FileCheckExpressionAST>>
+FileCheckPattern::parseNumericSubstitutionBlock(
+    StringRef Expr,
+    Optional<FileCheckNumericVariable *> &DefinedNumericVariable,
+    bool IsLegacyLineExpr, Optional<size_t> LineNumber,
+    FileCheckPatternContext *Context, const SourceMgr &SM) {
+  std::unique_ptr<FileCheckExpressionAST> ExpressionAST = nullptr;
+  StringRef DefExpr = StringRef();
+  DefinedNumericVariable = None;
+  // Save variable definition expression if any.
+  size_t DefEnd = Expr.find(':');
+  if (DefEnd != StringRef::npos) {
+    DefExpr = Expr.substr(0, DefEnd);
+    Expr = Expr.substr(DefEnd + 1);
+  }
+
+  // Parse the expression itself.
+  Expr = Expr.ltrim(SpaceChars);
+  if (!Expr.empty()) {
+    // The first operand in a legacy @LINE expression is always the @LINE
+    // pseudo variable.
+    AllowedOperand AO =
+        IsLegacyLineExpr ? AllowedOperand::LineVar : AllowedOperand::Any;
+    Expected<std::unique_ptr<FileCheckExpressionAST>> ParseResult =
+        parseNumericOperand(Expr, AO, LineNumber, Context, SM);
+    while (ParseResult && !Expr.empty()) {
+      ParseResult = parseBinop(Expr, std::move(*ParseResult), IsLegacyLineExpr,
+                               LineNumber, Context, SM);
+      // Legacy @LINE expressions only allow 2 operands.
+      if (ParseResult && IsLegacyLineExpr && !Expr.empty())
+        return FileCheckErrorDiagnostic::get(
+            SM, Expr,
+            "unexpected characters at end of expression '" + Expr + "'");
+    }
+    if (!ParseResult)
+      return ParseResult;
+    ExpressionAST = std::move(*ParseResult);
+  }
+
+  // Parse the numeric variable definition.
+  if (DefEnd != StringRef::npos) {
+    DefExpr = DefExpr.ltrim(SpaceChars);
+    Expected<FileCheckNumericVariable *> ParseResult =
+        parseNumericVariableDefinition(DefExpr, Context, LineNumber, SM);
+
+    if (!ParseResult)
+      return ParseResult.takeError();
+    DefinedNumericVariable = *ParseResult;
+  }
+
+  return std::move(ExpressionAST);
+}
+
+bool FileCheckPattern::parsePattern(StringRef PatternStr, StringRef Prefix,
+                                    SourceMgr &SM,
+                                    const FileCheckRequest &Req) {
+  bool MatchFullLinesHere = Req.MatchFullLines && CheckTy != Check::CheckNot;
+
+  PatternLoc = SMLoc::getFromPointer(PatternStr.data());
+
+  if (!(Req.NoCanonicalizeWhiteSpace && Req.MatchFullLines))
+    // Ignore trailing whitespace.
+    while (!PatternStr.empty() &&
+           (PatternStr.back() == ' ' || PatternStr.back() == '\t'))
+      PatternStr = PatternStr.substr(0, PatternStr.size() - 1);
+
+  // Check that there is something on the line.
+  if (PatternStr.empty() && CheckTy != Check::CheckEmpty) {
+    SM.PrintMessage(PatternLoc, SourceMgr::DK_Error,
+                    "found empty check string with prefix '" + Prefix + ":'");
+    return true;
+  }
+
+  if (!PatternStr.empty() && CheckTy == Check::CheckEmpty) {
+    SM.PrintMessage(
+        PatternLoc, SourceMgr::DK_Error,
+        "found non-empty check string for empty check with prefix '" + Prefix +
+            ":'");
+    return true;
+  }
+
+  if (CheckTy == Check::CheckEmpty) {
+    RegExStr = "(\n$)";
+    return false;
+  }
+
+  // Check to see if this is a fixed string, or if it has regex pieces.
+  if (!MatchFullLinesHere &&
+      (PatternStr.size() < 2 || (PatternStr.find("{{") == StringRef::npos &&
+                                 PatternStr.find("[[") == StringRef::npos))) {
+    FixedStr = PatternStr;
+    return false;
+  }
+
+  if (MatchFullLinesHere) {
+    RegExStr += '^';
+    if (!Req.NoCanonicalizeWhiteSpace)
+      RegExStr += " *";
+  }
+
+  // Paren value #0 is for the fully matched string.  Any new parenthesized
+  // values add from there.
+  unsigned CurParen = 1;
+
+  // Otherwise, there is at least one regex piece.  Build up the regex pattern
+  // by escaping scary characters in fixed strings, building up one big regex.
+  while (!PatternStr.empty()) {
+    // RegEx matches.
+    if (PatternStr.startswith("{{")) {
+      // This is the start of a regex match.  Scan for the }}.
+      size_t End = PatternStr.find("}}");
+      if (End == StringRef::npos) {
+        SM.PrintMessage(SMLoc::getFromPointer(PatternStr.data()),
+                        SourceMgr::DK_Error,
+                        "found start of regex string with no end '}}'");
+        return true;
+      }
+
+      // Enclose {{}} patterns in parens just like [[]] even though we're not
+      // capturing the result for any purpose.  This is required in case the
+      // expression contains an alternation like: CHECK:  abc{{x|z}}def.  We
+      // want this to turn into: "abc(x|z)def" not "abcx|zdef".
+      RegExStr += '(';
+      ++CurParen;
+
+      if (AddRegExToRegEx(PatternStr.substr(2, End - 2), CurParen, SM))
+        return true;
+      RegExStr += ')';
+
+      PatternStr = PatternStr.substr(End + 2);
+      continue;
+    }
+
+    // String and numeric substitution blocks. Pattern substitution blocks come
+    // in two forms: [[foo:.*]] and [[foo]]. The former matches .* (or some
+    // other regex) and assigns it to the string variable 'foo'. The latter
+    // substitutes foo's value. Numeric substitution blocks recognize the same
+    // form as string ones, but start with a '#' sign after the double
+    // brackets. They also accept a combined form which sets a numeric variable
+    // to the evaluation of an expression. Both string and numeric variable
+    // names must satisfy the regular expression "[a-zA-Z_][0-9a-zA-Z_]*" to be
+    // valid, as this helps catch some common errors.
+    if (PatternStr.startswith("[[")) {
+      StringRef UnparsedPatternStr = PatternStr.substr(2);
+      // Find the closing bracket pair ending the match.  End is going to be an
+      // offset relative to the beginning of the match string.
+      size_t End = FindRegexVarEnd(UnparsedPatternStr, SM);
+      StringRef MatchStr = UnparsedPatternStr.substr(0, End);
+      bool IsNumBlock = MatchStr.consume_front("#");
+
+      if (End == StringRef::npos) {
+        SM.PrintMessage(SMLoc::getFromPointer(PatternStr.data()),
+                        SourceMgr::DK_Error,
+                        "Invalid substitution block, no ]] found");
+        return true;
+      }
+      // Strip the substitution block we are parsing. End points to the start
+      // of the "]]" closing the expression so account for it in computing the
+      // index of the first unparsed character.
+      PatternStr = UnparsedPatternStr.substr(End + 2);
+
+      bool IsDefinition = false;
+      bool SubstNeeded = false;
+      // Whether the substitution block is a legacy use of @LINE with string
+      // substitution block syntax.
+      bool IsLegacyLineExpr = false;
+      StringRef DefName;
+      StringRef SubstStr;
+      StringRef MatchRegexp;
+      size_t SubstInsertIdx = RegExStr.size();
+
+      // Parse string variable or legacy @LINE expression.
+      if (!IsNumBlock) {
+        size_t VarEndIdx = MatchStr.find(":");
+        size_t SpacePos = MatchStr.substr(0, VarEndIdx).find_first_of(" \t");
+        if (SpacePos != StringRef::npos) {
+          SM.PrintMessage(SMLoc::getFromPointer(MatchStr.data() + SpacePos),
+                          SourceMgr::DK_Error, "unexpected whitespace");
+          return true;
+        }
+
+        // Get the name (e.g. "foo") and verify it is well formed.
+        StringRef OrigMatchStr = MatchStr;
+        Expected<FileCheckPattern::VariableProperties> ParseVarResult =
+            parseVariable(MatchStr, SM);
+        if (!ParseVarResult) {
+          logAllUnhandledErrors(ParseVarResult.takeError(), errs());
+          return true;
+        }
+        StringRef Name = ParseVarResult->Name;
+        bool IsPseudo = ParseVarResult->IsPseudo;
+
+        IsDefinition = (VarEndIdx != StringRef::npos);
+        SubstNeeded = !IsDefinition;
+        if (IsDefinition) {
+          if ((IsPseudo || !MatchStr.consume_front(":"))) {
+            SM.PrintMessage(SMLoc::getFromPointer(Name.data()),
+                            SourceMgr::DK_Error,
+                            "invalid name in string variable definition");
+            return true;
+          }
+
+          // Detect collisions between string and numeric variables when the
+          // former is created later than the latter.
+          if (Context->GlobalNumericVariableTable.find(Name) !=
+              Context->GlobalNumericVariableTable.end()) {
+            SM.PrintMessage(
+                SMLoc::getFromPointer(Name.data()), SourceMgr::DK_Error,
+                "numeric variable with name '" + Name + "' already exists");
+            return true;
+          }
+          DefName = Name;
+          MatchRegexp = MatchStr;
+        } else {
+          if (IsPseudo) {
+            MatchStr = OrigMatchStr;
+            IsLegacyLineExpr = IsNumBlock = true;
+          } else
+            SubstStr = Name;
+        }
+      }
+
+      // Parse numeric substitution block.
+      std::unique_ptr<FileCheckExpressionAST> ExpressionAST;
+      Optional<FileCheckNumericVariable *> DefinedNumericVariable;
+      if (IsNumBlock) {
+        Expected<std::unique_ptr<FileCheckExpressionAST>> ParseResult =
+            parseNumericSubstitutionBlock(MatchStr, DefinedNumericVariable,
+                                          IsLegacyLineExpr, LineNumber, Context,
+                                          SM);
+        if (!ParseResult) {
+          logAllUnhandledErrors(ParseResult.takeError(), errs());
+          return true;
+        }
+        ExpressionAST = std::move(*ParseResult);
+        SubstNeeded = ExpressionAST != nullptr;
+        if (DefinedNumericVariable) {
+          IsDefinition = true;
+          DefName = (*DefinedNumericVariable)->getName();
+        }
+        if (SubstNeeded)
+          SubstStr = MatchStr;
+        else
+          MatchRegexp = "[0-9]+";
+      }
+
+      // Handle variable definition: [[<def>:(...)]] and [[#(...)<def>:(...)]].
+      if (IsDefinition) {
+        RegExStr += '(';
+        ++SubstInsertIdx;
+
+        if (IsNumBlock) {
+          FileCheckNumericVariableMatch NumericVariableDefinition = {
+              *DefinedNumericVariable, CurParen};
+          NumericVariableDefs[DefName] = NumericVariableDefinition;
+          // This store is done here rather than in match() to allow
+          // parseNumericVariableUse() to get the pointer to the class instance
+          // of the right variable definition corresponding to a given numeric
+          // variable use.
+          Context->GlobalNumericVariableTable[DefName] =
+              *DefinedNumericVariable;
+        } else {
+          VariableDefs[DefName] = CurParen;
+          // Mark string variable as defined to detect collisions between
+          // string and numeric variables in parseNumericVariableUse() and
+          // defineCmdlineVariables() when the latter is created later than the
+          // former. We cannot reuse GlobalVariableTable for this by populating
+          // it with an empty string since we would then lose the ability to
+          // detect the use of an undefined variable in match().
+          Context->DefinedVariableTable[DefName] = true;
+        }
+
+        ++CurParen;
+      }
+
+      if (!MatchRegexp.empty() && AddRegExToRegEx(MatchRegexp, CurParen, SM))
+        return true;
+
+      if (IsDefinition)
+        RegExStr += ')';
+
+      // Handle substitutions: [[foo]] and [[#<foo expr>]].
+      if (SubstNeeded) {
+        // Handle substitution of string variables that were defined earlier on
+        // the same line by emitting a backreference. Expressions do not
+        // support substituting a numeric variable defined on the same line.
+        if (!IsNumBlock && VariableDefs.find(SubstStr) != VariableDefs.end()) {
+          unsigned CaptureParenGroup = VariableDefs[SubstStr];
+          if (CaptureParenGroup < 1 || CaptureParenGroup > 9) {
+            SM.PrintMessage(SMLoc::getFromPointer(SubstStr.data()),
+                            SourceMgr::DK_Error,
+                            "Can't back-reference more than 9 variables");
+            return true;
+          }
+          AddBackrefToRegEx(CaptureParenGroup);
+        } else {
+          // Handle substitution of string variables ([[<var>]]) defined in
+          // previous CHECK patterns, and substitution of expressions.
+          FileCheckSubstitution *Substitution =
+              IsNumBlock
+                  ? Context->makeNumericSubstitution(
+                        SubstStr, std::move(ExpressionAST), SubstInsertIdx)
+                  : Context->makeStringSubstitution(SubstStr, SubstInsertIdx);
+          Substitutions.push_back(Substitution);
+        }
+      }
+    }
+
+    // Handle fixed string matches.
+    // Find the end, which is the start of the next regex.
+    size_t FixedMatchEnd = PatternStr.find("{{");
+    FixedMatchEnd = std::min(FixedMatchEnd, PatternStr.find("[["));
+    RegExStr += Regex::escape(PatternStr.substr(0, FixedMatchEnd));
+    PatternStr = PatternStr.substr(FixedMatchEnd);
+  }
+
+  if (MatchFullLinesHere) {
+    if (!Req.NoCanonicalizeWhiteSpace)
+      RegExStr += " *";
+    RegExStr += '$';
+  }
+
+  return false;
+}
+
+bool FileCheckPattern::AddRegExToRegEx(StringRef RS, unsigned &CurParen, SourceMgr &SM) {
+  Regex R(RS);
+  std::string Error;
+  if (!R.isValid(Error)) {
+    SM.PrintMessage(SMLoc::getFromPointer(RS.data()), SourceMgr::DK_Error,
+                    "invalid regex: " + Error);
+    return true;
+  }
+
+  RegExStr += RS.str();
+  CurParen += R.getNumMatches();
+  return false;
+}
+
+void FileCheckPattern::AddBackrefToRegEx(unsigned BackrefNum) {
+  assert(BackrefNum >= 1 && BackrefNum <= 9 && "Invalid backref number");
+  std::string Backref = std::string("\\") + std::string(1, '0' + BackrefNum);
+  RegExStr += Backref;
+}
+
+Expected<size_t> FileCheckPattern::match(StringRef Buffer, size_t &MatchLen,
+                                         const SourceMgr &SM) const {
+  // If this is the EOF pattern, match it immediately.
+  if (CheckTy == Check::CheckEOF) {
+    MatchLen = 0;
+    return Buffer.size();
+  }
+
+  // If this is a fixed string pattern, just match it now.
+  if (!FixedStr.empty()) {
+    MatchLen = FixedStr.size();
+    size_t Pos = Buffer.find(FixedStr);
+    if (Pos == StringRef::npos)
+      return make_error<FileCheckNotFoundError>();
+    return Pos;
+  }
+
+  // Regex match.
+
+  // If there are substitutions, we need to create a temporary string with the
+  // actual value.
+  StringRef RegExToMatch = RegExStr;
+  std::string TmpStr;
+  if (!Substitutions.empty()) {
+    TmpStr = RegExStr;
+    if (LineNumber)
+      Context->LineVariable->setValue(*LineNumber);
+
+    size_t InsertOffset = 0;
+    // Substitute all string variables and expressions whose values are only
+    // now known. Use of string variables defined on the same line are handled
+    // by back-references.
+    for (const auto &Substitution : Substitutions) {
+      // Substitute and check for failure (e.g. use of undefined variable).
+      Expected<std::string> Value = Substitution->getResult();
+      if (!Value)
+        return Value.takeError();
+
+      // Plop it into the regex at the adjusted offset.
+      TmpStr.insert(TmpStr.begin() + Substitution->getIndex() + InsertOffset,
+                    Value->begin(), Value->end());
+      InsertOffset += Value->size();
+    }
+
+    // Match the newly constructed regex.
+    RegExToMatch = TmpStr;
+  }
+
+  SmallVector<StringRef, 4> MatchInfo;
+  if (!Regex(RegExToMatch, Regex::Newline).match(Buffer, &MatchInfo))
+    return make_error<FileCheckNotFoundError>();
+
+  // Successful regex match.
+  assert(!MatchInfo.empty() && "Didn't get any match");
+  StringRef FullMatch = MatchInfo[0];
+
+  // If this defines any string variables, remember their values.
+  for (const auto &VariableDef : VariableDefs) {
+    assert(VariableDef.second < MatchInfo.size() && "Internal paren error");
+    Context->GlobalVariableTable[VariableDef.first] =
+        MatchInfo[VariableDef.second];
+  }
+
+  // If this defines any numeric variables, remember their values.
+  for (const auto &NumericVariableDef : NumericVariableDefs) {
+    const FileCheckNumericVariableMatch &NumericVariableMatch =
+        NumericVariableDef.getValue();
+    unsigned CaptureParenGroup = NumericVariableMatch.CaptureParenGroup;
+    assert(CaptureParenGroup < MatchInfo.size() && "Internal paren error");
+    FileCheckNumericVariable *DefinedNumericVariable =
+        NumericVariableMatch.DefinedNumericVariable;
+
+    StringRef MatchedValue = MatchInfo[CaptureParenGroup];
+    uint64_t Val;
+    if (MatchedValue.getAsInteger(10, Val))
+      return FileCheckErrorDiagnostic::get(SM, MatchedValue,
+                                           "Unable to represent numeric value");
+    DefinedNumericVariable->setValue(Val);
+  }
+
+  // Like CHECK-NEXT, CHECK-EMPTY's match range is considered to start after
+  // the required preceding newline, which is consumed by the pattern in the
+  // case of CHECK-EMPTY but not CHECK-NEXT.
+  size_t MatchStartSkip = CheckTy == Check::CheckEmpty;
+  MatchLen = FullMatch.size() - MatchStartSkip;
+  return FullMatch.data() - Buffer.data() + MatchStartSkip;
+}
+
+unsigned FileCheckPattern::computeMatchDistance(StringRef Buffer) const {
+  // Just compute the number of matching characters. For regular expressions, we
+  // just compare against the regex itself and hope for the best.
+  //
+  // FIXME: One easy improvement here is have the regex lib generate a single
+  // example regular expression which matches, and use that as the example
+  // string.
+  StringRef ExampleString(FixedStr);
+  if (ExampleString.empty())
+    ExampleString = RegExStr;
+
+  // Only compare up to the first line in the buffer, or the string size.
+  StringRef BufferPrefix = Buffer.substr(0, ExampleString.size());
+  BufferPrefix = BufferPrefix.split('\n').first;
+  return BufferPrefix.edit_distance(ExampleString);
+}
+
+void FileCheckPattern::printSubstitutions(const SourceMgr &SM, StringRef Buffer,
+                                          SMRange MatchRange) const {
+  // Print what we know about substitutions.
+  if (!Substitutions.empty()) {
+    for (const auto &Substitution : Substitutions) {
+      SmallString<256> Msg;
+      raw_svector_ostream OS(Msg);
+      Expected<std::string> MatchedValue = Substitution->getResult();
+
+      // Substitution failed or is not known at match time, print the undefined
+      // variables it uses.
+      if (!MatchedValue) {
+        bool UndefSeen = false;
+        handleAllErrors(MatchedValue.takeError(),
+                        [](const FileCheckNotFoundError &E) {},
+                        // Handled in PrintNoMatch().
+                        [](const FileCheckErrorDiagnostic &E) {},
+                        [&](const FileCheckUndefVarError &E) {
+                          if (!UndefSeen) {
+                            OS << "uses undefined variable(s):";
+                            UndefSeen = true;
+                          }
+                          OS << " ";
+                          E.log(OS);
+                        });
+      } else {
+        // Substitution succeeded. Print substituted value.
+        OS << "with \"";
+        OS.write_escaped(Substitution->getFromString()) << "\" equal to \"";
+        OS.write_escaped(*MatchedValue) << "\"";
+      }
+
+      if (MatchRange.isValid())
+        SM.PrintMessage(MatchRange.Start, SourceMgr::DK_Note, OS.str(),
+                        {MatchRange});
+      else
+        SM.PrintMessage(SMLoc::getFromPointer(Buffer.data()),
+                        SourceMgr::DK_Note, OS.str());
+    }
+  }
+}
+
+static SMRange ProcessMatchResult(FileCheckDiag::MatchType MatchTy,
+                                  const SourceMgr &SM, SMLoc Loc,
+                                  Check::FileCheckType CheckTy,
+                                  StringRef Buffer, size_t Pos, size_t Len,
+                                  std::vector<FileCheckDiag> *Diags,
+                                  bool AdjustPrevDiag = false) {
+  SMLoc Start = SMLoc::getFromPointer(Buffer.data() + Pos);
+  SMLoc End = SMLoc::getFromPointer(Buffer.data() + Pos + Len);
+  SMRange Range(Start, End);
+  if (Diags) {
+    if (AdjustPrevDiag)
+      Diags->rbegin()->MatchTy = MatchTy;
+    else
+      Diags->emplace_back(SM, CheckTy, Loc, MatchTy, Range);
+  }
+  return Range;
+}
+
+void FileCheckPattern::printFuzzyMatch(
+    const SourceMgr &SM, StringRef Buffer,
+    std::vector<FileCheckDiag> *Diags) const {
+  // Attempt to find the closest/best fuzzy match.  Usually an error happens
+  // because some string in the output didn't exactly match. In these cases, we
+  // would like to show the user a best guess at what "should have" matched, to
+  // save them having to actually check the input manually.
+  size_t NumLinesForward = 0;
+  size_t Best = StringRef::npos;
+  double BestQuality = 0;
+
+  // Use an arbitrary 4k limit on how far we will search.
+  for (size_t i = 0, e = std::min(size_t(4096), Buffer.size()); i != e; ++i) {
+    if (Buffer[i] == '\n')
+      ++NumLinesForward;
+
+    // Patterns have leading whitespace stripped, so skip whitespace when
+    // looking for something which looks like a pattern.
+    if (Buffer[i] == ' ' || Buffer[i] == '\t')
+      continue;
+
+    // Compute the "quality" of this match as an arbitrary combination of the
+    // match distance and the number of lines skipped to get to this match.
+    unsigned Distance = computeMatchDistance(Buffer.substr(i));
+    double Quality = Distance + (NumLinesForward / 100.);
+
+    if (Quality < BestQuality || Best == StringRef::npos) {
+      Best = i;
+      BestQuality = Quality;
+    }
+  }
+
+  // Print the "possible intended match here" line if we found something
+  // reasonable and not equal to what we showed in the "scanning from here"
+  // line.
+  if (Best && Best != StringRef::npos && BestQuality < 50) {
+    SMRange MatchRange =
+        ProcessMatchResult(FileCheckDiag::MatchFuzzy, SM, getLoc(),
+                           getCheckTy(), Buffer, Best, 0, Diags);
+    SM.PrintMessage(MatchRange.Start, SourceMgr::DK_Note,
+                    "possible intended match here");
+
+    // FIXME: If we wanted to be really friendly we would show why the match
+    // failed, as it can be hard to spot simple one character differences.
+  }
+}
+
+Expected<StringRef>
+FileCheckPatternContext::getPatternVarValue(StringRef VarName) {
+  auto VarIter = GlobalVariableTable.find(VarName);
+  if (VarIter == GlobalVariableTable.end())
+    return make_error<FileCheckUndefVarError>(VarName);
+
+  return VarIter->second;
+}
+
+template <class... Types>
+FileCheckNumericVariable *
+FileCheckPatternContext::makeNumericVariable(Types... args) {
+  NumericVariables.push_back(
+      std::make_unique<FileCheckNumericVariable>(args...));
+  return NumericVariables.back().get();
+}
+
+FileCheckSubstitution *
+FileCheckPatternContext::makeStringSubstitution(StringRef VarName,
+                                                size_t InsertIdx) {
+  Substitutions.push_back(
+      std::make_unique<FileCheckStringSubstitution>(this, VarName, InsertIdx));
+  return Substitutions.back().get();
+}
+
+FileCheckSubstitution *FileCheckPatternContext::makeNumericSubstitution(
+    StringRef ExpressionStr,
+    std::unique_ptr<FileCheckExpressionAST> ExpressionAST, size_t InsertIdx) {
+  Substitutions.push_back(std::make_unique<FileCheckNumericSubstitution>(
+      this, ExpressionStr, std::move(ExpressionAST), InsertIdx));
+  return Substitutions.back().get();
+}
+
+size_t FileCheckPattern::FindRegexVarEnd(StringRef Str, SourceMgr &SM) {
+  // Offset keeps track of the current offset within the input Str
+  size_t Offset = 0;
+  // [...] Nesting depth
+  size_t BracketDepth = 0;
+
+  while (!Str.empty()) {
+    if (Str.startswith("]]") && BracketDepth == 0)
+      return Offset;
+    if (Str[0] == '\\') {
+      // Backslash escapes the next char within regexes, so skip them both.
+      Str = Str.substr(2);
+      Offset += 2;
+    } else {
+      switch (Str[0]) {
+      default:
+        break;
+      case '[':
+        BracketDepth++;
+        break;
+      case ']':
+        if (BracketDepth == 0) {
+          SM.PrintMessage(SMLoc::getFromPointer(Str.data()),
+                          SourceMgr::DK_Error,
+                          "missing closing \"]\" for regex variable");
+          exit(1);
+        }
+        BracketDepth--;
+        break;
+      }
+      Str = Str.substr(1);
+      Offset++;
+    }
+  }
+
+  return StringRef::npos;
+}
+
+StringRef FileCheck::CanonicalizeFile(MemoryBuffer &MB,
+                                      SmallVectorImpl<char> &OutputBuffer) {
+  OutputBuffer.reserve(MB.getBufferSize());
+
+  for (const char *Ptr = MB.getBufferStart(), *End = MB.getBufferEnd();
+       Ptr != End; ++Ptr) {
+    // Eliminate trailing dosish \r.
+    if (Ptr <= End - 2 && Ptr[0] == '\r' && Ptr[1] == '\n') {
+      continue;
+    }
+
+    // If current char is not a horizontal whitespace or if horizontal
+    // whitespace canonicalization is disabled, dump it to output as is.
+    if (Req.NoCanonicalizeWhiteSpace || (*Ptr != ' ' && *Ptr != '\t')) {
+      OutputBuffer.push_back(*Ptr);
+      continue;
+    }
+
+    // Otherwise, add one space and advance over neighboring space.
+    OutputBuffer.push_back(' ');
+    while (Ptr + 1 != End && (Ptr[1] == ' ' || Ptr[1] == '\t'))
+      ++Ptr;
+  }
+
+  // Add a null byte and then return all but that byte.
+  OutputBuffer.push_back('\0');
+  return StringRef(OutputBuffer.data(), OutputBuffer.size() - 1);
+}
+
+FileCheckDiag::FileCheckDiag(const SourceMgr &SM,
+                             const Check::FileCheckType &CheckTy,
+                             SMLoc CheckLoc, MatchType MatchTy,
+                             SMRange InputRange)
+    : CheckTy(CheckTy), MatchTy(MatchTy) {
+  auto Start = SM.getLineAndColumn(InputRange.Start);
+  auto End = SM.getLineAndColumn(InputRange.End);
+  InputStartLine = Start.first;
+  InputStartCol = Start.second;
+  InputEndLine = End.first;
+  InputEndCol = End.second;
+  Start = SM.getLineAndColumn(CheckLoc);
+  CheckLine = Start.first;
+  CheckCol = Start.second;
+}
+
+static bool IsPartOfWord(char c) {
+  return (isalnum(c) || c == '-' || c == '_');
+}
+
+Check::FileCheckType &Check::FileCheckType::setCount(int C) {
+  assert(Count > 0 && "zero and negative counts are not supported");
+  assert((C == 1 || Kind == CheckPlain) &&
+         "count supported only for plain CHECK directives");
+  Count = C;
+  return *this;
+}
+
+std::string Check::FileCheckType::getDescription(StringRef Prefix) const {
+  switch (Kind) {
+  case Check::CheckNone:
+    return "invalid";
+  case Check::CheckPlain:
+    if (Count > 1)
+      return Prefix.str() + "-COUNT";
+    return Prefix;
+  case Check::CheckNext:
+    return Prefix.str() + "-NEXT";
+  case Check::CheckSame:
+    return Prefix.str() + "-SAME";
+  case Check::CheckNot:
+    return Prefix.str() + "-NOT";
+  case Check::CheckDAG:
+    return Prefix.str() + "-DAG";
+  case Check::CheckLabel:
+    return Prefix.str() + "-LABEL";
+  case Check::CheckEmpty:
+    return Prefix.str() + "-EMPTY";
+  case Check::CheckEOF:
+    return "implicit EOF";
+  case Check::CheckBadNot:
+    return "bad NOT";
+  case Check::CheckBadCount:
+    return "bad COUNT";
+  }
+  llvm_unreachable("unknown FileCheckType");
+}
+
+static std::pair<Check::FileCheckType, StringRef>
+FindCheckType(StringRef Buffer, StringRef Prefix) {
+  if (Buffer.size() <= Prefix.size())
+    return {Check::CheckNone, StringRef()};
+
+  char NextChar = Buffer[Prefix.size()];
+
+  StringRef Rest = Buffer.drop_front(Prefix.size() + 1);
+  // Verify that the : is present after the prefix.
+  if (NextChar == ':')
+    return {Check::CheckPlain, Rest};
+
+  if (NextChar != '-')
+    return {Check::CheckNone, StringRef()};
+
+  if (Rest.consume_front("COUNT-")) {
+    int64_t Count;
+    if (Rest.consumeInteger(10, Count))
+      // Error happened in parsing integer.
+      return {Check::CheckBadCount, Rest};
+    if (Count <= 0 || Count > INT32_MAX)
+      return {Check::CheckBadCount, Rest};
+    if (!Rest.consume_front(":"))
+      return {Check::CheckBadCount, Rest};
+    return {Check::FileCheckType(Check::CheckPlain).setCount(Count), Rest};
+  }
+
+  if (Rest.consume_front("NEXT:"))
+    return {Check::CheckNext, Rest};
+
+  if (Rest.consume_front("SAME:"))
+    return {Check::CheckSame, Rest};
+
+  if (Rest.consume_front("NOT:"))
+    return {Check::CheckNot, Rest};
+
+  if (Rest.consume_front("DAG:"))
+    return {Check::CheckDAG, Rest};
+
+  if (Rest.consume_front("LABEL:"))
+    return {Check::CheckLabel, Rest};
+
+  if (Rest.consume_front("EMPTY:"))
+    return {Check::CheckEmpty, Rest};
+
+  // You can't combine -NOT with another suffix.
+  if (Rest.startswith("DAG-NOT:") || Rest.startswith("NOT-DAG:") ||
+      Rest.startswith("NEXT-NOT:") || Rest.startswith("NOT-NEXT:") ||
+      Rest.startswith("SAME-NOT:") || Rest.startswith("NOT-SAME:") ||
+      Rest.startswith("EMPTY-NOT:") || Rest.startswith("NOT-EMPTY:"))
+    return {Check::CheckBadNot, Rest};
+
+  return {Check::CheckNone, Rest};
+}
+
+// From the given position, find the next character after the word.
+static size_t SkipWord(StringRef Str, size_t Loc) {
+  while (Loc < Str.size() && IsPartOfWord(Str[Loc]))
+    ++Loc;
+  return Loc;
+}
+
+/// Searches the buffer for the first prefix in the prefix regular expression.
+///
+/// This searches the buffer using the provided regular expression, however it
+/// enforces constraints beyond that:
+/// 1) The found prefix must not be a suffix of something that looks like
+///    a valid prefix.
+/// 2) The found prefix must be followed by a valid check type suffix using \c
+///    FindCheckType above.
+///
+/// \returns a pair of StringRefs into the Buffer, which combines:
+///   - the first match of the regular expression to satisfy these two is
+///   returned,
+///     otherwise an empty StringRef is returned to indicate failure.
+///   - buffer rewound to the location right after parsed suffix, for parsing
+///     to continue from
+///
+/// If this routine returns a valid prefix, it will also shrink \p Buffer to
+/// start at the beginning of the returned prefix, increment \p LineNumber for
+/// each new line consumed from \p Buffer, and set \p CheckTy to the type of
+/// check found by examining the suffix.
+///
+/// If no valid prefix is found, the state of Buffer, LineNumber, and CheckTy
+/// is unspecified.
+static std::pair<StringRef, StringRef>
+FindFirstMatchingPrefix(Regex &PrefixRE, StringRef &Buffer,
+                        unsigned &LineNumber, Check::FileCheckType &CheckTy) {
+  SmallVector<StringRef, 2> Matches;
+
+  while (!Buffer.empty()) {
+    // Find the first (longest) match using the RE.
+    if (!PrefixRE.match(Buffer, &Matches))
+      // No match at all, bail.
+      return {StringRef(), StringRef()};
+
+    StringRef Prefix = Matches[0];
+    Matches.clear();
+
+    assert(Prefix.data() >= Buffer.data() &&
+           Prefix.data() < Buffer.data() + Buffer.size() &&
+           "Prefix doesn't start inside of buffer!");
+    size_t Loc = Prefix.data() - Buffer.data();
+    StringRef Skipped = Buffer.substr(0, Loc);
+    Buffer = Buffer.drop_front(Loc);
+    LineNumber += Skipped.count('\n');
+
+    // Check that the matched prefix isn't a suffix of some other check-like
+    // word.
+    // FIXME: This is a very ad-hoc check. it would be better handled in some
+    // other way. Among other things it seems hard to distinguish between
+    // intentional and unintentional uses of this feature.
+    if (Skipped.empty() || !IsPartOfWord(Skipped.back())) {
+      // Now extract the type.
+      StringRef AfterSuffix;
+      std::tie(CheckTy, AfterSuffix) = FindCheckType(Buffer, Prefix);
+
+      // If we've found a valid check type for this prefix, we're done.
+      if (CheckTy != Check::CheckNone)
+        return {Prefix, AfterSuffix};
+    }
+
+    // If we didn't successfully find a prefix, we need to skip this invalid
+    // prefix and continue scanning. We directly skip the prefix that was
+    // matched and any additional parts of that check-like word.
+    Buffer = Buffer.drop_front(SkipWord(Buffer, Prefix.size()));
+  }
+
+  // We ran out of buffer while skipping partial matches so give up.
+  return {StringRef(), StringRef()};
+}
+
+void FileCheckPatternContext::createLineVariable() {
+  assert(!LineVariable && "@LINE pseudo numeric variable already created");
+  StringRef LineName = "@LINE";
+  LineVariable = makeNumericVariable(LineName);
+  GlobalNumericVariableTable[LineName] = LineVariable;
+}
+
+FileCheck::FileCheck(FileCheckRequest Req)
+    : Req(Req), PatternContext(std::make_unique<FileCheckPatternContext>()),
+      CheckStrings(std::make_unique<std::vector<FileCheckString>>()) {}
+
+FileCheck::~FileCheck() = default;
+
+bool FileCheck::readCheckFile(SourceMgr &SM, StringRef Buffer,
+                              Regex &PrefixRE) {
+  Error DefineError =
+      PatternContext->defineCmdlineVariables(Req.GlobalDefines, SM);
+  if (DefineError) {
+    logAllUnhandledErrors(std::move(DefineError), errs());
+    return true;
+  }
+
+  PatternContext->createLineVariable();
+
+  std::vector<FileCheckPattern> ImplicitNegativeChecks;
+  for (const auto &PatternString : Req.ImplicitCheckNot) {
+    // Create a buffer with fake command line content in order to display the
+    // command line option responsible for the specific implicit CHECK-NOT.
+    std::string Prefix = "-implicit-check-not='";
+    std::string Suffix = "'";
+    std::unique_ptr<MemoryBuffer> CmdLine = MemoryBuffer::getMemBufferCopy(
+        Prefix + PatternString + Suffix, "command line");
+
+    StringRef PatternInBuffer =
+        CmdLine->getBuffer().substr(Prefix.size(), PatternString.size());
+    SM.AddNewSourceBuffer(std::move(CmdLine), SMLoc());
+
+    ImplicitNegativeChecks.push_back(
+        FileCheckPattern(Check::CheckNot, PatternContext.get()));
+    ImplicitNegativeChecks.back().parsePattern(PatternInBuffer,
+                                               "IMPLICIT-CHECK", SM, Req);
+  }
+
+  std::vector<FileCheckPattern> DagNotMatches = ImplicitNegativeChecks;
+
+  // LineNumber keeps track of the line on which CheckPrefix instances are
+  // found.
+  unsigned LineNumber = 1;
+
+  while (1) {
+    Check::FileCheckType CheckTy;
+
+    // See if a prefix occurs in the memory buffer.
+    StringRef UsedPrefix;
+    StringRef AfterSuffix;
+    std::tie(UsedPrefix, AfterSuffix) =
+        FindFirstMatchingPrefix(PrefixRE, Buffer, LineNumber, CheckTy);
+    if (UsedPrefix.empty())
+      break;
+    assert(UsedPrefix.data() == Buffer.data() &&
+           "Failed to move Buffer's start forward, or pointed prefix outside "
+           "of the buffer!");
+    assert(AfterSuffix.data() >= Buffer.data() &&
+           AfterSuffix.data() < Buffer.data() + Buffer.size() &&
+           "Parsing after suffix doesn't start inside of buffer!");
+
+    // Location to use for error messages.
+    const char *UsedPrefixStart = UsedPrefix.data();
+
+    // Skip the buffer to the end of parsed suffix (or just prefix, if no good
+    // suffix was processed).
+    Buffer = AfterSuffix.empty() ? Buffer.drop_front(UsedPrefix.size())
+                                 : AfterSuffix;
+
+    // Complain about useful-looking but unsupported suffixes.
+    if (CheckTy == Check::CheckBadNot) {
+      SM.PrintMessage(SMLoc::getFromPointer(Buffer.data()), SourceMgr::DK_Error,
+                      "unsupported -NOT combo on prefix '" + UsedPrefix + "'");
+      return true;
+    }
+
+    // Complain about invalid count specification.
+    if (CheckTy == Check::CheckBadCount) {
+      SM.PrintMessage(SMLoc::getFromPointer(Buffer.data()), SourceMgr::DK_Error,
+                      "invalid count in -COUNT specification on prefix '" +
+                          UsedPrefix + "'");
+      return true;
+    }
+
+    // Okay, we found the prefix, yay. Remember the rest of the line, but ignore
+    // leading whitespace.
+    if (!(Req.NoCanonicalizeWhiteSpace && Req.MatchFullLines))
+      Buffer = Buffer.substr(Buffer.find_first_not_of(" \t"));
+
+    // Scan ahead to the end of line.
+    size_t EOL = Buffer.find_first_of("\n\r");
+
+    // Remember the location of the start of the pattern, for diagnostics.
+    SMLoc PatternLoc = SMLoc::getFromPointer(Buffer.data());
+
+    // Parse the pattern.
+    FileCheckPattern P(CheckTy, PatternContext.get(), LineNumber);
+    if (P.parsePattern(Buffer.substr(0, EOL), UsedPrefix, SM, Req))
+      return true;
+
+    // Verify that CHECK-LABEL lines do not define or use variables
+    if ((CheckTy == Check::CheckLabel) && P.hasVariable()) {
+      SM.PrintMessage(
+          SMLoc::getFromPointer(UsedPrefixStart), SourceMgr::DK_Error,
+          "found '" + UsedPrefix + "-LABEL:'"
+                                   " with variable definition or use");
+      return true;
+    }
+
+    Buffer = Buffer.substr(EOL);
+
+    // Verify that CHECK-NEXT/SAME/EMPTY lines have at least one CHECK line before them.
+    if ((CheckTy == Check::CheckNext || CheckTy == Check::CheckSame ||
+         CheckTy == Check::CheckEmpty) &&
+        CheckStrings->empty()) {
+      StringRef Type = CheckTy == Check::CheckNext
+                           ? "NEXT"
+                           : CheckTy == Check::CheckEmpty ? "EMPTY" : "SAME";
+      SM.PrintMessage(SMLoc::getFromPointer(UsedPrefixStart),
+                      SourceMgr::DK_Error,
+                      "found '" + UsedPrefix + "-" + Type +
+                          "' without previous '" + UsedPrefix + ": line");
+      return true;
+    }
+
+    // Handle CHECK-DAG/-NOT.
+    if (CheckTy == Check::CheckDAG || CheckTy == Check::CheckNot) {
+      DagNotMatches.push_back(P);
+      continue;
+    }
+
+    // Okay, add the string we captured to the output vector and move on.
+    CheckStrings->emplace_back(P, UsedPrefix, PatternLoc);
+    std::swap(DagNotMatches, CheckStrings->back().DagNotStrings);
+    DagNotMatches = ImplicitNegativeChecks;
+  }
+
+  // Add an EOF pattern for any trailing CHECK-DAG/-NOTs, and use the first
+  // prefix as a filler for the error message.
+  if (!DagNotMatches.empty()) {
+    CheckStrings->emplace_back(
+        FileCheckPattern(Check::CheckEOF, PatternContext.get(), LineNumber + 1),
+        *Req.CheckPrefixes.begin(), SMLoc::getFromPointer(Buffer.data()));
+    std::swap(DagNotMatches, CheckStrings->back().DagNotStrings);
+  }
+
+  if (CheckStrings->empty()) {
+    errs() << "error: no check strings found with prefix"
+           << (Req.CheckPrefixes.size() > 1 ? "es " : " ");
+    auto I = Req.CheckPrefixes.begin();
+    auto E = Req.CheckPrefixes.end();
+    if (I != E) {
+      errs() << "\'" << *I << ":'";
+      ++I;
+    }
+    for (; I != E; ++I)
+      errs() << ", \'" << *I << ":'";
+
+    errs() << '\n';
+    return true;
+  }
+
+  return false;
+}
+
+static void PrintMatch(bool ExpectedMatch, const SourceMgr &SM,
+                       StringRef Prefix, SMLoc Loc, const FileCheckPattern &Pat,
+                       int MatchedCount, StringRef Buffer, size_t MatchPos,
+                       size_t MatchLen, const FileCheckRequest &Req,
+                       std::vector<FileCheckDiag> *Diags) {
+  bool PrintDiag = true;
+  if (ExpectedMatch) {
+    if (!Req.Verbose)
+      return;
+    if (!Req.VerboseVerbose && Pat.getCheckTy() == Check::CheckEOF)
+      return;
+    // Due to their verbosity, we don't print verbose diagnostics here if we're
+    // gathering them for a different rendering, but we always print other
+    // diagnostics.
+    PrintDiag = !Diags;
+  }
+  SMRange MatchRange = ProcessMatchResult(
+      ExpectedMatch ? FileCheckDiag::MatchFoundAndExpected
+                    : FileCheckDiag::MatchFoundButExcluded,
+      SM, Loc, Pat.getCheckTy(), Buffer, MatchPos, MatchLen, Diags);
+  if (!PrintDiag)
+    return;
+
+  std::string Message = formatv("{0}: {1} string found in input",
+                                Pat.getCheckTy().getDescription(Prefix),
+                                (ExpectedMatch ? "expected" : "excluded"))
+                            .str();
+  if (Pat.getCount() > 1)
+    Message += formatv(" ({0} out of {1})", MatchedCount, Pat.getCount()).str();
+
+  SM.PrintMessage(
+      Loc, ExpectedMatch ? SourceMgr::DK_Remark : SourceMgr::DK_Error, Message);
+  SM.PrintMessage(MatchRange.Start, SourceMgr::DK_Note, "found here",
+                  {MatchRange});
+  Pat.printSubstitutions(SM, Buffer, MatchRange);
+}
+
+static void PrintMatch(bool ExpectedMatch, const SourceMgr &SM,
+                       const FileCheckString &CheckStr, int MatchedCount,
+                       StringRef Buffer, size_t MatchPos, size_t MatchLen,
+                       FileCheckRequest &Req,
+                       std::vector<FileCheckDiag> *Diags) {
+  PrintMatch(ExpectedMatch, SM, CheckStr.Prefix, CheckStr.Loc, CheckStr.Pat,
+             MatchedCount, Buffer, MatchPos, MatchLen, Req, Diags);
+}
+
+static void PrintNoMatch(bool ExpectedMatch, const SourceMgr &SM,
+                         StringRef Prefix, SMLoc Loc,
+                         const FileCheckPattern &Pat, int MatchedCount,
+                         StringRef Buffer, bool VerboseVerbose,
+                         std::vector<FileCheckDiag> *Diags, Error MatchErrors) {
+  assert(MatchErrors && "Called on successful match");
+  bool PrintDiag = true;
+  if (!ExpectedMatch) {
+    if (!VerboseVerbose) {
+      consumeError(std::move(MatchErrors));
+      return;
+    }
+    // Due to their verbosity, we don't print verbose diagnostics here if we're
+    // gathering them for a different rendering, but we always print other
+    // diagnostics.
+    PrintDiag = !Diags;
+  }
+
+  // If the current position is at the end of a line, advance to the start of
+  // the next line.
+  Buffer = Buffer.substr(Buffer.find_first_not_of(" \t\n\r"));
+  SMRange SearchRange = ProcessMatchResult(
+      ExpectedMatch ? FileCheckDiag::MatchNoneButExpected
+                    : FileCheckDiag::MatchNoneAndExcluded,
+      SM, Loc, Pat.getCheckTy(), Buffer, 0, Buffer.size(), Diags);
+  if (!PrintDiag) {
+    consumeError(std::move(MatchErrors));
+    return;
+  }
+
+  MatchErrors =
+      handleErrors(std::move(MatchErrors),
+                   [](const FileCheckErrorDiagnostic &E) { E.log(errs()); });
+
+  // No problem matching the string per se.
+  if (!MatchErrors)
+    return;
+  consumeError(std::move(MatchErrors));
+
+  // Print "not found" diagnostic.
+  std::string Message = formatv("{0}: {1} string not found in input",
+                                Pat.getCheckTy().getDescription(Prefix),
+                                (ExpectedMatch ? "expected" : "excluded"))
+                            .str();
+  if (Pat.getCount() > 1)
+    Message += formatv(" ({0} out of {1})", MatchedCount, Pat.getCount()).str();
+  SM.PrintMessage(
+      Loc, ExpectedMatch ? SourceMgr::DK_Error : SourceMgr::DK_Remark, Message);
+
+  // Print the "scanning from here" line.
+  SM.PrintMessage(SearchRange.Start, SourceMgr::DK_Note, "scanning from here");
+
+  // Allow the pattern to print additional information if desired.
+  Pat.printSubstitutions(SM, Buffer);
+
+  if (ExpectedMatch)
+    Pat.printFuzzyMatch(SM, Buffer, Diags);
+}
+
+static void PrintNoMatch(bool ExpectedMatch, const SourceMgr &SM,
+                         const FileCheckString &CheckStr, int MatchedCount,
+                         StringRef Buffer, bool VerboseVerbose,
+                         std::vector<FileCheckDiag> *Diags, Error MatchErrors) {
+  PrintNoMatch(ExpectedMatch, SM, CheckStr.Prefix, CheckStr.Loc, CheckStr.Pat,
+               MatchedCount, Buffer, VerboseVerbose, Diags,
+               std::move(MatchErrors));
+}
+
+/// Counts the number of newlines in the specified range.
+static unsigned CountNumNewlinesBetween(StringRef Range,
+                                        const char *&FirstNewLine) {
+  unsigned NumNewLines = 0;
+  while (1) {
+    // Scan for newline.
+    Range = Range.substr(Range.find_first_of("\n\r"));
+    if (Range.empty())
+      return NumNewLines;
+
+    ++NumNewLines;
+
+    // Handle \n\r and \r\n as a single newline.
+    if (Range.size() > 1 && (Range[1] == '\n' || Range[1] == '\r') &&
+        (Range[0] != Range[1]))
+      Range = Range.substr(1);
+    Range = Range.substr(1);
+
+    if (NumNewLines == 1)
+      FirstNewLine = Range.begin();
+  }
+}
+
+size_t FileCheckString::Check(const SourceMgr &SM, StringRef Buffer,
+                              bool IsLabelScanMode, size_t &MatchLen,
+                              FileCheckRequest &Req,
+                              std::vector<FileCheckDiag> *Diags) const {
+  size_t LastPos = 0;
+  std::vector<const FileCheckPattern *> NotStrings;
+
+  // IsLabelScanMode is true when we are scanning forward to find CHECK-LABEL
+  // bounds; we have not processed variable definitions within the bounded block
+  // yet so cannot handle any final CHECK-DAG yet; this is handled when going
+  // over the block again (including the last CHECK-LABEL) in normal mode.
+  if (!IsLabelScanMode) {
+    // Match "dag strings" (with mixed "not strings" if any).
+    LastPos = CheckDag(SM, Buffer, NotStrings, Req, Diags);
+    if (LastPos == StringRef::npos)
+      return StringRef::npos;
+  }
+
+  // Match itself from the last position after matching CHECK-DAG.
+  size_t LastMatchEnd = LastPos;
+  size_t FirstMatchPos = 0;
+  // Go match the pattern Count times. Majority of patterns only match with
+  // count 1 though.
+  assert(Pat.getCount() != 0 && "pattern count can not be zero");
+  for (int i = 1; i <= Pat.getCount(); i++) {
+    StringRef MatchBuffer = Buffer.substr(LastMatchEnd);
+    size_t CurrentMatchLen;
+    // get a match at current start point
+    Expected<size_t> MatchResult = Pat.match(MatchBuffer, CurrentMatchLen, SM);
+
+    // report
+    if (!MatchResult) {
+      PrintNoMatch(true, SM, *this, i, MatchBuffer, Req.VerboseVerbose, Diags,
+                   MatchResult.takeError());
+      return StringRef::npos;
+    }
+    size_t MatchPos = *MatchResult;
+    PrintMatch(true, SM, *this, i, MatchBuffer, MatchPos, CurrentMatchLen, Req,
+               Diags);
+    if (i == 1)
+      FirstMatchPos = LastPos + MatchPos;
+
+    // move start point after the match
+    LastMatchEnd += MatchPos + CurrentMatchLen;
+  }
+  // Full match len counts from first match pos.
+  MatchLen = LastMatchEnd - FirstMatchPos;
+
+  // Similar to the above, in "label-scan mode" we can't yet handle CHECK-NEXT
+  // or CHECK-NOT
+  if (!IsLabelScanMode) {
+    size_t MatchPos = FirstMatchPos - LastPos;
+    StringRef MatchBuffer = Buffer.substr(LastPos);
+    StringRef SkippedRegion = Buffer.substr(LastPos, MatchPos);
+
+    // If this check is a "CHECK-NEXT", verify that the previous match was on
+    // the previous line (i.e. that there is one newline between them).
+    if (CheckNext(SM, SkippedRegion)) {
+      ProcessMatchResult(FileCheckDiag::MatchFoundButWrongLine, SM, Loc,
+                         Pat.getCheckTy(), MatchBuffer, MatchPos, MatchLen,
+                         Diags, Req.Verbose);
+      return StringRef::npos;
+    }
+
+    // If this check is a "CHECK-SAME", verify that the previous match was on
+    // the same line (i.e. that there is no newline between them).
+    if (CheckSame(SM, SkippedRegion)) {
+      ProcessMatchResult(FileCheckDiag::MatchFoundButWrongLine, SM, Loc,
+                         Pat.getCheckTy(), MatchBuffer, MatchPos, MatchLen,
+                         Diags, Req.Verbose);
+      return StringRef::npos;
+    }
+
+    // If this match had "not strings", verify that they don't exist in the
+    // skipped region.
+    if (CheckNot(SM, SkippedRegion, NotStrings, Req, Diags))
+      return StringRef::npos;
+  }
+
+  return FirstMatchPos;
+}
+
+bool FileCheckString::CheckNext(const SourceMgr &SM, StringRef Buffer) const {
+  if (Pat.getCheckTy() != Check::CheckNext &&
+      Pat.getCheckTy() != Check::CheckEmpty)
+    return false;
+
+  Twine CheckName =
+      Prefix +
+      Twine(Pat.getCheckTy() == Check::CheckEmpty ? "-EMPTY" : "-NEXT");
+
+  // Count the number of newlines between the previous match and this one.
+  const char *FirstNewLine = nullptr;
+  unsigned NumNewLines = CountNumNewlinesBetween(Buffer, FirstNewLine);
+
+  if (NumNewLines == 0) {
+    SM.PrintMessage(Loc, SourceMgr::DK_Error,
+                    CheckName + ": is on the same line as previous match");
+    SM.PrintMessage(SMLoc::getFromPointer(Buffer.end()), SourceMgr::DK_Note,
+                    "'next' match was here");
+    SM.PrintMessage(SMLoc::getFromPointer(Buffer.data()), SourceMgr::DK_Note,
+                    "previous match ended here");
+    return true;
+  }
+
+  if (NumNewLines != 1) {
+    SM.PrintMessage(Loc, SourceMgr::DK_Error,
+                    CheckName +
+                        ": is not on the line after the previous match");
+    SM.PrintMessage(SMLoc::getFromPointer(Buffer.end()), SourceMgr::DK_Note,
+                    "'next' match was here");
+    SM.PrintMessage(SMLoc::getFromPointer(Buffer.data()), SourceMgr::DK_Note,
+                    "previous match ended here");
+    SM.PrintMessage(SMLoc::getFromPointer(FirstNewLine), SourceMgr::DK_Note,
+                    "non-matching line after previous match is here");
+    return true;
+  }
+
+  return false;
+}
+
+bool FileCheckString::CheckSame(const SourceMgr &SM, StringRef Buffer) const {
+  if (Pat.getCheckTy() != Check::CheckSame)
+    return false;
+
+  // Count the number of newlines between the previous match and this one.
+  const char *FirstNewLine = nullptr;
+  unsigned NumNewLines = CountNumNewlinesBetween(Buffer, FirstNewLine);
+
+  if (NumNewLines != 0) {
+    SM.PrintMessage(Loc, SourceMgr::DK_Error,
+                    Prefix +
+                        "-SAME: is not on the same line as the previous match");
+    SM.PrintMessage(SMLoc::getFromPointer(Buffer.end()), SourceMgr::DK_Note,
+                    "'next' match was here");
+    SM.PrintMessage(SMLoc::getFromPointer(Buffer.data()), SourceMgr::DK_Note,
+                    "previous match ended here");
+    return true;
+  }
+
+  return false;
+}
+
+bool FileCheckString::CheckNot(
+    const SourceMgr &SM, StringRef Buffer,
+    const std::vector<const FileCheckPattern *> &NotStrings,
+    const FileCheckRequest &Req, std::vector<FileCheckDiag> *Diags) const {
+  for (const FileCheckPattern *Pat : NotStrings) {
+    assert((Pat->getCheckTy() == Check::CheckNot) && "Expect CHECK-NOT!");
+
+    size_t MatchLen = 0;
+    Expected<size_t> MatchResult = Pat->match(Buffer, MatchLen, SM);
+
+    if (!MatchResult) {
+      PrintNoMatch(false, SM, Prefix, Pat->getLoc(), *Pat, 1, Buffer,
+                   Req.VerboseVerbose, Diags, MatchResult.takeError());
+      continue;
+    }
+    size_t Pos = *MatchResult;
+
+    PrintMatch(false, SM, Prefix, Pat->getLoc(), *Pat, 1, Buffer, Pos, MatchLen,
+               Req, Diags);
+
+    return true;
+  }
+
+  return false;
+}
+
+size_t
+FileCheckString::CheckDag(const SourceMgr &SM, StringRef Buffer,
+                          std::vector<const FileCheckPattern *> &NotStrings,
+                          const FileCheckRequest &Req,
+                          std::vector<FileCheckDiag> *Diags) const {
+  if (DagNotStrings.empty())
+    return 0;
+
+  // The start of the search range.
+  size_t StartPos = 0;
+
+  struct MatchRange {
+    size_t Pos;
+    size_t End;
+  };
+  // A sorted list of ranges for non-overlapping CHECK-DAG matches.  Match
+  // ranges are erased from this list once they are no longer in the search
+  // range.
+  std::list<MatchRange> MatchRanges;
+
+  // We need PatItr and PatEnd later for detecting the end of a CHECK-DAG
+  // group, so we don't use a range-based for loop here.
+  for (auto PatItr = DagNotStrings.begin(), PatEnd = DagNotStrings.end();
+       PatItr != PatEnd; ++PatItr) {
+    const FileCheckPattern &Pat = *PatItr;
+    assert((Pat.getCheckTy() == Check::CheckDAG ||
+            Pat.getCheckTy() == Check::CheckNot) &&
+           "Invalid CHECK-DAG or CHECK-NOT!");
+
+    if (Pat.getCheckTy() == Check::CheckNot) {
+      NotStrings.push_back(&Pat);
+      continue;
+    }
+
+    assert((Pat.getCheckTy() == Check::CheckDAG) && "Expect CHECK-DAG!");
+
+    // CHECK-DAG always matches from the start.
+    size_t MatchLen = 0, MatchPos = StartPos;
+
+    // Search for a match that doesn't overlap a previous match in this
+    // CHECK-DAG group.
+    for (auto MI = MatchRanges.begin(), ME = MatchRanges.end(); true; ++MI) {
+      StringRef MatchBuffer = Buffer.substr(MatchPos);
+      Expected<size_t> MatchResult = Pat.match(MatchBuffer, MatchLen, SM);
+      // With a group of CHECK-DAGs, a single mismatching means the match on
+      // that group of CHECK-DAGs fails immediately.
+      if (!MatchResult) {
+        PrintNoMatch(true, SM, Prefix, Pat.getLoc(), Pat, 1, MatchBuffer,
+                     Req.VerboseVerbose, Diags, MatchResult.takeError());
+        return StringRef::npos;
+      }
+      size_t MatchPosBuf = *MatchResult;
+      // Re-calc it as the offset relative to the start of the original string.
+      MatchPos += MatchPosBuf;
+      if (Req.VerboseVerbose)
+        PrintMatch(true, SM, Prefix, Pat.getLoc(), Pat, 1, Buffer, MatchPos,
+                   MatchLen, Req, Diags);
+      MatchRange M{MatchPos, MatchPos + MatchLen};
+      if (Req.AllowDeprecatedDagOverlap) {
+        // We don't need to track all matches in this mode, so we just maintain
+        // one match range that encompasses the current CHECK-DAG group's
+        // matches.
+        if (MatchRanges.empty())
+          MatchRanges.insert(MatchRanges.end(), M);
+        else {
+          auto Block = MatchRanges.begin();
+          Block->Pos = std::min(Block->Pos, M.Pos);
+          Block->End = std::max(Block->End, M.End);
+        }
+        break;
+      }
+      // Iterate previous matches until overlapping match or insertion point.
+      bool Overlap = false;
+      for (; MI != ME; ++MI) {
+        if (M.Pos < MI->End) {
+          // !Overlap => New match has no overlap and is before this old match.
+          // Overlap => New match overlaps this old match.
+          Overlap = MI->Pos < M.End;
+          break;
+        }
+      }
+      if (!Overlap) {
+        // Insert non-overlapping match into list.
+        MatchRanges.insert(MI, M);
+        break;
+      }
+      if (Req.VerboseVerbose) {
+        // Due to their verbosity, we don't print verbose diagnostics here if
+        // we're gathering them for a different rendering, but we always print
+        // other diagnostics.
+        if (!Diags) {
+          SMLoc OldStart = SMLoc::getFromPointer(Buffer.data() + MI->Pos);
+          SMLoc OldEnd = SMLoc::getFromPointer(Buffer.data() + MI->End);
+          SMRange OldRange(OldStart, OldEnd);
+          SM.PrintMessage(OldStart, SourceMgr::DK_Note,
+                          "match discarded, overlaps earlier DAG match here",
+                          {OldRange});
+        } else
+          Diags->rbegin()->MatchTy = FileCheckDiag::MatchFoundButDiscarded;
+      }
+      MatchPos = MI->End;
+    }
+    if (!Req.VerboseVerbose)
+      PrintMatch(true, SM, Prefix, Pat.getLoc(), Pat, 1, Buffer, MatchPos,
+                 MatchLen, Req, Diags);
+
+    // Handle the end of a CHECK-DAG group.
+    if (std::next(PatItr) == PatEnd ||
+        std::next(PatItr)->getCheckTy() == Check::CheckNot) {
+      if (!NotStrings.empty()) {
+        // If there are CHECK-NOTs between two CHECK-DAGs or from CHECK to
+        // CHECK-DAG, verify that there are no 'not' strings occurred in that
+        // region.
+        StringRef SkippedRegion =
+            Buffer.slice(StartPos, MatchRanges.begin()->Pos);
+        if (CheckNot(SM, SkippedRegion, NotStrings, Req, Diags))
+          return StringRef::npos;
+        // Clear "not strings".
+        NotStrings.clear();
+      }
+      // All subsequent CHECK-DAGs and CHECK-NOTs should be matched from the
+      // end of this CHECK-DAG group's match range.
+      StartPos = MatchRanges.rbegin()->End;
+      // Don't waste time checking for (impossible) overlaps before that.
+      MatchRanges.clear();
+    }
+  }
+
+  return StartPos;
+}
+
+// A check prefix must contain only alphanumeric, hyphens and underscores.
+static bool ValidateCheckPrefix(StringRef CheckPrefix) {
+  static const Regex Validator("^[a-zA-Z0-9_-]*$");
+  return Validator.match(CheckPrefix);
+}
+
+bool FileCheck::ValidateCheckPrefixes() {
+  StringSet<> PrefixSet;
+
+  for (StringRef Prefix : Req.CheckPrefixes) {
+    // Reject empty prefixes.
+    if (Prefix == "")
+      return false;
+
+    if (!PrefixSet.insert(Prefix).second)
+      return false;
+
+    if (!ValidateCheckPrefix(Prefix))
+      return false;
+  }
+
+  return true;
+}
+
+Regex FileCheck::buildCheckPrefixRegex() {
+  // I don't think there's a way to specify an initial value for cl::list,
+  // so if nothing was specified, add the default
+  if (Req.CheckPrefixes.empty())
+    Req.CheckPrefixes.push_back("CHECK");
+
+  // We already validated the contents of CheckPrefixes so just concatenate
+  // them as alternatives.
+  SmallString<32> PrefixRegexStr;
+  for (StringRef Prefix : Req.CheckPrefixes) {
+    if (Prefix != Req.CheckPrefixes.front())
+      PrefixRegexStr.push_back('|');
+
+    PrefixRegexStr.append(Prefix);
+  }
+
+  return Regex(PrefixRegexStr);
+}
+
+Error FileCheckPatternContext::defineCmdlineVariables(
+    std::vector<std::string> &CmdlineDefines, SourceMgr &SM) {
+  assert(GlobalVariableTable.empty() && GlobalNumericVariableTable.empty() &&
+         "Overriding defined variable with command-line variable definitions");
+
+  if (CmdlineDefines.empty())
+    return Error::success();
+
+  // Create a string representing the vector of command-line definitions. Each
+  // definition is on its own line and prefixed with a definition number to
+  // clarify which definition a given diagnostic corresponds to.
+  unsigned I = 0;
+  Error Errs = Error::success();
+  std::string CmdlineDefsDiag;
+  SmallVector<std::pair<size_t, size_t>, 4> CmdlineDefsIndices;
+  for (StringRef CmdlineDef : CmdlineDefines) {
+    std::string DefPrefix = ("Global define #" + Twine(++I) + ": ").str();
+    size_t EqIdx = CmdlineDef.find('=');
+    if (EqIdx == StringRef::npos) {
+      CmdlineDefsIndices.push_back(std::make_pair(CmdlineDefsDiag.size(), 0));
+      continue;
+    }
+    // Numeric variable definition.
+    if (CmdlineDef[0] == '#') {
+      // Append a copy of the command-line definition adapted to use the same
+      // format as in the input file to be able to reuse
+      // parseNumericSubstitutionBlock.
+      CmdlineDefsDiag += (DefPrefix + CmdlineDef + " (parsed as: [[").str();
+      std::string SubstitutionStr = CmdlineDef;
+      SubstitutionStr[EqIdx] = ':';
+      CmdlineDefsIndices.push_back(
+          std::make_pair(CmdlineDefsDiag.size(), SubstitutionStr.size()));
+      CmdlineDefsDiag += (SubstitutionStr + Twine("]])\n")).str();
+    } else {
+      CmdlineDefsDiag += DefPrefix;
+      CmdlineDefsIndices.push_back(
+          std::make_pair(CmdlineDefsDiag.size(), CmdlineDef.size()));
+      CmdlineDefsDiag += (CmdlineDef + "\n").str();
+    }
+  }
+
+  // Create a buffer with fake command line content in order to display
+  // parsing diagnostic with location information and point to the
+  // global definition with invalid syntax.
+  std::unique_ptr<MemoryBuffer> CmdLineDefsDiagBuffer =
+      MemoryBuffer::getMemBufferCopy(CmdlineDefsDiag, "Global defines");
+  StringRef CmdlineDefsDiagRef = CmdLineDefsDiagBuffer->getBuffer();
+  SM.AddNewSourceBuffer(std::move(CmdLineDefsDiagBuffer), SMLoc());
+
+  for (std::pair<size_t, size_t> CmdlineDefIndices : CmdlineDefsIndices) {
+    StringRef CmdlineDef = CmdlineDefsDiagRef.substr(CmdlineDefIndices.first,
+                                                     CmdlineDefIndices.second);
+    if (CmdlineDef.empty()) {
+      Errs = joinErrors(
+          std::move(Errs),
+          FileCheckErrorDiagnostic::get(
+              SM, CmdlineDef, "missing equal sign in global definition"));
+      continue;
+    }
+
+    // Numeric variable definition.
+    if (CmdlineDef[0] == '#') {
+      // Now parse the definition both to check that the syntax is correct and
+      // to create the necessary class instance.
+      StringRef CmdlineDefExpr = CmdlineDef.substr(1);
+      Optional<FileCheckNumericVariable *> DefinedNumericVariable;
+      Expected<std::unique_ptr<FileCheckExpressionAST>> ExpressionASTResult =
+          FileCheckPattern::parseNumericSubstitutionBlock(
+              CmdlineDefExpr, DefinedNumericVariable, false, None, this, SM);
+      if (!ExpressionASTResult) {
+        Errs = joinErrors(std::move(Errs), ExpressionASTResult.takeError());
+        continue;
+      }
+      std::unique_ptr<FileCheckExpressionAST> ExpressionAST =
+          std::move(*ExpressionASTResult);
+      // Now evaluate the expression whose value this variable should be set
+      // to, since the expression of a command-line variable definition should
+      // only use variables defined earlier on the command-line. If not, this
+      // is an error and we report it.
+      Expected<uint64_t> Value = ExpressionAST->eval();
+      if (!Value) {
+        Errs = joinErrors(std::move(Errs), Value.takeError());
+        continue;
+      }
+
+      assert(DefinedNumericVariable && "No variable defined");
+      (*DefinedNumericVariable)->setValue(*Value);
+
+      // Record this variable definition.
+      GlobalNumericVariableTable[(*DefinedNumericVariable)->getName()] =
+          *DefinedNumericVariable;
+    } else {
+      // String variable definition.
+      std::pair<StringRef, StringRef> CmdlineNameVal = CmdlineDef.split('=');
+      StringRef CmdlineName = CmdlineNameVal.first;
+      StringRef OrigCmdlineName = CmdlineName;
+      Expected<FileCheckPattern::VariableProperties> ParseVarResult =
+          FileCheckPattern::parseVariable(CmdlineName, SM);
+      if (!ParseVarResult) {
+        Errs = joinErrors(std::move(Errs), ParseVarResult.takeError());
+        continue;
+      }
+      // Check that CmdlineName does not denote a pseudo variable is only
+      // composed of the parsed numeric variable. This catches cases like
+      // "FOO+2" in a "FOO+2=10" definition.
+      if (ParseVarResult->IsPseudo || !CmdlineName.empty()) {
+        Errs = joinErrors(std::move(Errs),
+                          FileCheckErrorDiagnostic::get(
+                              SM, OrigCmdlineName,
+                              "invalid name in string variable definition '" +
+                                  OrigCmdlineName + "'"));
+        continue;
+      }
+      StringRef Name = ParseVarResult->Name;
+
+      // Detect collisions between string and numeric variables when the former
+      // is created later than the latter.
+      if (GlobalNumericVariableTable.find(Name) !=
+          GlobalNumericVariableTable.end()) {
+        Errs = joinErrors(std::move(Errs), FileCheckErrorDiagnostic::get(
+                                               SM, Name,
+                                               "numeric variable with name '" +
+                                                   Name + "' already exists"));
+        continue;
+      }
+      GlobalVariableTable.insert(CmdlineNameVal);
+      // Mark the string variable as defined to detect collisions between
+      // string and numeric variables in defineCmdlineVariables when the latter
+      // is created later than the former. We cannot reuse GlobalVariableTable
+      // for this by populating it with an empty string since we would then
+      // lose the ability to detect the use of an undefined variable in
+      // match().
+      DefinedVariableTable[Name] = true;
+    }
+  }
+
+  return Errs;
+}
+
+void FileCheckPatternContext::clearLocalVars() {
+  SmallVector<StringRef, 16> LocalPatternVars, LocalNumericVars;
+  for (const StringMapEntry<StringRef> &Var : GlobalVariableTable)
+    if (Var.first()[0] != '$')
+      LocalPatternVars.push_back(Var.first());
+
+  // Numeric substitution reads the value of a variable directly, not via
+  // GlobalNumericVariableTable. Therefore, we clear local variables by
+  // clearing their value which will lead to a numeric substitution failure. We
+  // also mark the variable for removal from GlobalNumericVariableTable since
+  // this is what defineCmdlineVariables checks to decide that no global
+  // variable has been defined.
+  for (const auto &Var : GlobalNumericVariableTable)
+    if (Var.first()[0] != '$') {
+      Var.getValue()->clearValue();
+      LocalNumericVars.push_back(Var.first());
+    }
+
+  for (const auto &Var : LocalPatternVars)
+    GlobalVariableTable.erase(Var);
+  for (const auto &Var : LocalNumericVars)
+    GlobalNumericVariableTable.erase(Var);
+}
+
+bool FileCheck::checkInput(SourceMgr &SM, StringRef Buffer,
+                           std::vector<FileCheckDiag> *Diags) {
+  bool ChecksFailed = false;
+
+  unsigned i = 0, j = 0, e = CheckStrings->size();
+  while (true) {
+    StringRef CheckRegion;
+    if (j == e) {
+      CheckRegion = Buffer;
+    } else {
+      const FileCheckString &CheckLabelStr = (*CheckStrings)[j];
+      if (CheckLabelStr.Pat.getCheckTy() != Check::CheckLabel) {
+        ++j;
+        continue;
+      }
+
+      // Scan to next CHECK-LABEL match, ignoring CHECK-NOT and CHECK-DAG
+      size_t MatchLabelLen = 0;
+      size_t MatchLabelPos =
+          CheckLabelStr.Check(SM, Buffer, true, MatchLabelLen, Req, Diags);
+      if (MatchLabelPos == StringRef::npos)
+        // Immediately bail if CHECK-LABEL fails, nothing else we can do.
+        return false;
+
+      CheckRegion = Buffer.substr(0, MatchLabelPos + MatchLabelLen);
+      Buffer = Buffer.substr(MatchLabelPos + MatchLabelLen);
+      ++j;
+    }
+
+    // Do not clear the first region as it's the one before the first
+    // CHECK-LABEL and it would clear variables defined on the command-line
+    // before they get used.
+    if (i != 0 && Req.EnableVarScope)
+      PatternContext->clearLocalVars();
+
+    for (; i != j; ++i) {
+      const FileCheckString &CheckStr = (*CheckStrings)[i];
+
+      // Check each string within the scanned region, including a second check
+      // of any final CHECK-LABEL (to verify CHECK-NOT and CHECK-DAG)
+      size_t MatchLen = 0;
+      size_t MatchPos =
+          CheckStr.Check(SM, CheckRegion, false, MatchLen, Req, Diags);
+
+      if (MatchPos == StringRef::npos) {
+        ChecksFailed = true;
+        i = j;
+        break;
+      }
+
+      CheckRegion = CheckRegion.substr(MatchPos + MatchLen);
+    }
+
+    if (j == e)
+      break;
+  }
+
+  // Success if no checks failed.
+  return !ChecksFailed;
+}