Move llvm-tblgen's StringMatcher into the TableGen library so it can
be used by clang-tblgen.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156000 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/TableGen/StringMatcher.cpp b/lib/TableGen/StringMatcher.cpp
new file mode 100644
index 0000000..0ce626d
--- /dev/null
+++ b/lib/TableGen/StringMatcher.cpp
@@ -0,0 +1,149 @@
+//===- StringMatcher.cpp - Generate a matcher for input strings -----------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the StringMatcher class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/TableGen/StringMatcher.h"
+#include "llvm/Support/raw_ostream.h"
+#include <map>
+using namespace llvm;
+
+/// FindFirstNonCommonLetter - Find the first character in the keys of the
+/// string pairs that is not shared across the whole set of strings. All
+/// strings are assumed to have the same length.
+static unsigned
+FindFirstNonCommonLetter(const std::vector<const
+ StringMatcher::StringPair*> &Matches) {
+ assert(!Matches.empty());
+ for (unsigned i = 0, e = Matches[0]->first.size(); i != e; ++i) {
+ // Check to see if letter i is the same across the set.
+ char Letter = Matches[0]->first[i];
+
+ for (unsigned str = 0, e = Matches.size(); str != e; ++str)
+ if (Matches[str]->first[i] != Letter)
+ return i;
+ }
+
+ return Matches[0]->first.size();
+}
+
+/// EmitStringMatcherForChar - Given a set of strings that are known to be the
+/// same length and whose characters leading up to CharNo are the same, emit
+/// code to verify that CharNo and later are the same.
+///
+/// \return - True if control can leave the emitted code fragment.
+bool StringMatcher::
+EmitStringMatcherForChar(const std::vector<const StringPair*> &Matches,
+ unsigned CharNo, unsigned IndentCount) const {
+ assert(!Matches.empty() && "Must have at least one string to match!");
+ std::string Indent(IndentCount*2+4, ' ');
+
+ // If we have verified that the entire string matches, we're done: output the
+ // matching code.
+ if (CharNo == Matches[0]->first.size()) {
+ assert(Matches.size() == 1 && "Had duplicate keys to match on");
+
+ // If the to-execute code has \n's in it, indent each subsequent line.
+ StringRef Code = Matches[0]->second;
+
+ std::pair<StringRef, StringRef> Split = Code.split('\n');
+ OS << Indent << Split.first << "\t // \"" << Matches[0]->first << "\"\n";
+
+ Code = Split.second;
+ while (!Code.empty()) {
+ Split = Code.split('\n');
+ OS << Indent << Split.first << "\n";
+ Code = Split.second;
+ }
+ return false;
+ }
+
+ // Bucket the matches by the character we are comparing.
+ std::map<char, std::vector<const StringPair*> > MatchesByLetter;
+
+ for (unsigned i = 0, e = Matches.size(); i != e; ++i)
+ MatchesByLetter[Matches[i]->first[CharNo]].push_back(Matches[i]);
+
+
+ // If we have exactly one bucket to match, see how many characters are common
+ // across the whole set and match all of them at once.
+ if (MatchesByLetter.size() == 1) {
+ unsigned FirstNonCommonLetter = FindFirstNonCommonLetter(Matches);
+ unsigned NumChars = FirstNonCommonLetter-CharNo;
+
+ // Emit code to break out if the prefix doesn't match.
+ if (NumChars == 1) {
+ // Do the comparison with if (Str[1] != 'f')
+ // FIXME: Need to escape general characters.
+ OS << Indent << "if (" << StrVariableName << "[" << CharNo << "] != '"
+ << Matches[0]->first[CharNo] << "')\n";
+ OS << Indent << " break;\n";
+ } else {
+ // Do the comparison with if (Str.substr(1, 3) != "foo").
+ // FIXME: Need to escape general strings.
+ OS << Indent << "if (" << StrVariableName << ".substr(" << CharNo << ", "
+ << NumChars << ") != \"";
+ OS << Matches[0]->first.substr(CharNo, NumChars) << "\")\n";
+ OS << Indent << " break;\n";
+ }
+
+ return EmitStringMatcherForChar(Matches, FirstNonCommonLetter, IndentCount);
+ }
+
+ // Otherwise, we have multiple possible things, emit a switch on the
+ // character.
+ OS << Indent << "switch (" << StrVariableName << "[" << CharNo << "]) {\n";
+ OS << Indent << "default: break;\n";
+
+ for (std::map<char, std::vector<const StringPair*> >::iterator LI =
+ MatchesByLetter.begin(), E = MatchesByLetter.end(); LI != E; ++LI) {
+ // TODO: escape hard stuff (like \n) if we ever care about it.
+ OS << Indent << "case '" << LI->first << "':\t // "
+ << LI->second.size() << " string";
+ if (LI->second.size() != 1) OS << 's';
+ OS << " to match.\n";
+ if (EmitStringMatcherForChar(LI->second, CharNo+1, IndentCount+1))
+ OS << Indent << " break;\n";
+ }
+
+ OS << Indent << "}\n";
+ return true;
+}
+
+
+/// Emit - Top level entry point.
+///
+void StringMatcher::Emit(unsigned Indent) const {
+ // If nothing to match, just fall through.
+ if (Matches.empty()) return;
+
+ // First level categorization: group strings by length.
+ std::map<unsigned, std::vector<const StringPair*> > MatchesByLength;
+
+ for (unsigned i = 0, e = Matches.size(); i != e; ++i)
+ MatchesByLength[Matches[i].first.size()].push_back(&Matches[i]);
+
+ // Output a switch statement on length and categorize the elements within each
+ // bin.
+ OS.indent(Indent*2+2) << "switch (" << StrVariableName << ".size()) {\n";
+ OS.indent(Indent*2+2) << "default: break;\n";
+
+ for (std::map<unsigned, std::vector<const StringPair*> >::iterator LI =
+ MatchesByLength.begin(), E = MatchesByLength.end(); LI != E; ++LI) {
+ OS.indent(Indent*2+2) << "case " << LI->first << ":\t // "
+ << LI->second.size()
+ << " string" << (LI->second.size() == 1 ? "" : "s") << " to match.\n";
+ if (EmitStringMatcherForChar(LI->second, 0, Indent))
+ OS.indent(Indent*2+4) << "break;\n";
+ }
+
+ OS.indent(Indent*2+2) << "}\n";
+}