Consistently use MemoryLocation::UnknownSize to indicate unknown access size

1. Change the software pipeliner to use unknown size instead of dropping
   memory operands. It used to do it before, but MachineInstr::mayAlias
   did not handle it correctly.
2. Recognize UnknownSize in MachineInstr::mayAlias.
3. Print and parse UnknownSize in MIR.

Differential Revision: https://reviews.llvm.org/D50339

llvm-svn: 340208
diff --git a/llvm/lib/CodeGen/MIRParser/MILexer.cpp b/llvm/lib/CodeGen/MIRParser/MILexer.cpp
index 400e098..e3f19f0 100644
--- a/llvm/lib/CodeGen/MIRParser/MILexer.cpp
+++ b/llvm/lib/CodeGen/MIRParser/MILexer.cpp
@@ -247,6 +247,7 @@
       .Case("intpred", MIToken::kw_intpred)
       .Case("pre-instr-symbol", MIToken::kw_pre_instr_symbol)
       .Case("post-instr-symbol", MIToken::kw_post_instr_symbol)
+      .Case("unknown-size", MIToken::kw_unknown_size)
       .Default(MIToken::Identifier);
 }
 
diff --git a/llvm/lib/CodeGen/MIRParser/MILexer.h b/llvm/lib/CodeGen/MIRParser/MILexer.h
index 94b460e..d2dc551 100644
--- a/llvm/lib/CodeGen/MIRParser/MILexer.h
+++ b/llvm/lib/CodeGen/MIRParser/MILexer.h
@@ -115,6 +115,7 @@
     kw_intpred,
     kw_pre_instr_symbol,
     kw_post_instr_symbol,
+    kw_unknown_size,
 
     // Named metadata keywords
     md_tbaa,
diff --git a/llvm/lib/CodeGen/MIRParser/MIParser.cpp b/llvm/lib/CodeGen/MIRParser/MIParser.cpp
index 956f6ec..7ba75c1 100644
--- a/llvm/lib/CodeGen/MIRParser/MIParser.cpp
+++ b/llvm/lib/CodeGen/MIRParser/MIParser.cpp
@@ -24,6 +24,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/ADT/Twine.h"
+#include "llvm/Analysis/MemoryLocation.h"
 #include "llvm/AsmParser/Parser.h"
 #include "llvm/AsmParser/SlotMapping.h"
 #include "llvm/CodeGen/MIRPrinter.h"
@@ -2452,7 +2453,7 @@
     return false;
   }
 
-  return error("expected an atomic scope, ordering or a size integer literal");
+  return error("expected an atomic scope, ordering or a size specification");
 }
 
 bool MIParser::parseMachineMemoryOperand(MachineMemOperand *&Dest) {
@@ -2491,11 +2492,17 @@
   if (parseOptionalAtomicOrdering(FailureOrder))
     return true;
 
-  if (Token.isNot(MIToken::IntegerLiteral))
-    return error("expected the size integer literal after memory operation");
+  if (Token.isNot(MIToken::IntegerLiteral) &&
+      Token.isNot(MIToken::kw_unknown_size))
+    return error("expected the size integer literal or 'unknown-size' after "
+                 "memory operation");
   uint64_t Size;
-  if (getUint64(Size))
-    return true;
+  if (Token.is(MIToken::IntegerLiteral)) {
+    if (getUint64(Size))
+      return true;
+  } else if (Token.is(MIToken::kw_unknown_size)) {
+    Size = MemoryLocation::UnknownSize;
+  }
   lex();
 
   MachinePointerInfo Ptr = MachinePointerInfo();
@@ -2512,7 +2519,7 @@
     if (parseMachinePointerInfo(Ptr))
       return true;
   }
-  unsigned BaseAlignment = Size;
+  unsigned BaseAlignment = (Size != MemoryLocation::UnknownSize ? Size : 1);
   AAMDNodes AAInfo;
   MDNode *Range = nullptr;
   while (consumeIfPresent(MIToken::comma)) {
diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp
index 9503537..55dbbd3 100644
--- a/llvm/lib/CodeGen/MachineInstr.cpp
+++ b/llvm/lib/CodeGen/MachineInstr.cpp
@@ -1179,10 +1179,13 @@
 
   int64_t OffsetA = MMOa->getOffset();
   int64_t OffsetB = MMOb->getOffset();
-
   int64_t MinOffset = std::min(OffsetA, OffsetB);
-  int64_t WidthA = MMOa->getSize();
-  int64_t WidthB = MMOb->getSize();
+
+  uint64_t WidthA = MMOa->getSize();
+  uint64_t WidthB = MMOb->getSize();
+  bool KnownWidthA = WidthA != MemoryLocation::UnknownSize;
+  bool KnownWidthB = WidthB != MemoryLocation::UnknownSize;
+
   const Value *ValA = MMOa->getValue();
   const Value *ValB = MMOb->getValue();
   bool SameVal = (ValA && ValB && (ValA == ValB));
@@ -1198,6 +1201,8 @@
   }
 
   if (SameVal) {
+    if (!KnownWidthA || !KnownWidthB)
+      return true;
     int64_t MaxOffset = std::max(OffsetA, OffsetB);
     int64_t LowWidth = (MinOffset == OffsetA) ? WidthA : WidthB;
     return (MinOffset + LowWidth > MaxOffset);
@@ -1212,13 +1217,15 @@
   assert((OffsetA >= 0) && "Negative MachineMemOperand offset");
   assert((OffsetB >= 0) && "Negative MachineMemOperand offset");
 
-  int64_t Overlapa = WidthA + OffsetA - MinOffset;
-  int64_t Overlapb = WidthB + OffsetB - MinOffset;
+  int64_t OverlapA = KnownWidthA ? WidthA + OffsetA - MinOffset
+                                 : MemoryLocation::UnknownSize;
+  int64_t OverlapB = KnownWidthB ? WidthB + OffsetB - MinOffset
+                                 : MemoryLocation::UnknownSize;
 
   AliasResult AAResult = AA->alias(
-      MemoryLocation(ValA, Overlapa,
+      MemoryLocation(ValA, OverlapA,
                      UseTBAA ? MMOa->getAAInfo() : AAMDNodes()),
-      MemoryLocation(ValB, Overlapb,
+      MemoryLocation(ValB, OverlapB,
                      UseTBAA ? MMOb->getAAInfo() : AAMDNodes()));
 
   return (AAResult != NoAlias);
diff --git a/llvm/lib/CodeGen/MachineOperand.cpp b/llvm/lib/CodeGen/MachineOperand.cpp
index 8098333..a116d8f 100644
--- a/llvm/lib/CodeGen/MachineOperand.cpp
+++ b/llvm/lib/CodeGen/MachineOperand.cpp
@@ -14,6 +14,7 @@
 #include "llvm/CodeGen/MachineOperand.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Analysis/Loads.h"
+#include "llvm/Analysis/MemoryLocation.h"
 #include "llvm/CodeGen/MIRPrinter.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineJumpTableInfo.h"
@@ -1078,7 +1079,11 @@
   if (getFailureOrdering() != AtomicOrdering::NotAtomic)
     OS << toIRString(getFailureOrdering()) << ' ';
 
-  OS << getSize();
+  if (getSize() == MemoryLocation::UnknownSize)
+    OS << "unknown-size";
+  else
+    OS << getSize();
+
   if (const Value *Val = getValue()) {
     OS << ((isLoad() && isStore()) ? " on " : isLoad() ? " from " : " into ");
     printIRValueReference(OS, *Val, MST);
diff --git a/llvm/lib/CodeGen/MachinePipeliner.cpp b/llvm/lib/CodeGen/MachinePipeliner.cpp
index 943a2b4..c8d2c49 100644
--- a/llvm/lib/CodeGen/MachinePipeliner.cpp
+++ b/llvm/lib/CodeGen/MachinePipeliner.cpp
@@ -3190,8 +3190,8 @@
       NewMMOs.push_back(
           MF.getMachineMemOperand(MMO, AdjOffset, MMO->getSize()));
     } else {
-      NewMI.dropMemRefs(MF);
-      return;
+      NewMMOs.push_back(
+          MF.getMachineMemOperand(MMO, 0, MemoryLocation::UnknownSize));
     }
   }
   NewMI.setMemRefs(MF, NewMMOs);