Re-land MachineInstr: Reason locally about some memory objects before going to AA.
Summary:
Reverts r311008 to reinstate r310825 with a fix.
Refine alias checking for pseudo vs value to be conservative.
This fixes the original failure in builtbot unittest SingleSource/UnitTests/2003-07-09-SignedArgs.
Reviewers: hfinkel, nemanjai, efriedma
Reviewed By: efriedma
Subscribers: bjope, mcrosier, nhaehnle, javed.absar, llvm-commits
Differential Revision: https://reviews.llvm.org/D36900
llvm-svn: 312126
diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp
index 8bf1eb9..47926d6 100644
--- a/llvm/lib/CodeGen/MachineInstr.cpp
+++ b/llvm/lib/CodeGen/MachineInstr.cpp
@@ -1663,6 +1663,7 @@
bool UseTBAA) {
const MachineFunction *MF = getParent()->getParent();
const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
+ const MachineFrameInfo &MFI = MF->getFrameInfo();
// If neither instruction stores to memory, they can't alias in any
// meaningful way, even if they read from the same address.
@@ -1673,9 +1674,6 @@
if (TII->areMemAccessesTriviallyDisjoint(*this, Other, AA))
return false;
- if (!AA)
- return true;
-
// FIXME: Need to handle multiple memory operands to support all targets.
if (!hasOneMemOperand() || !Other.hasOneMemOperand())
return true;
@@ -1683,9 +1681,6 @@
MachineMemOperand *MMOa = *memoperands_begin();
MachineMemOperand *MMOb = *Other.memoperands_begin();
- if (!MMOa->getValue() || !MMOb->getValue())
- return true;
-
// The following interface to AA is fashioned after DAGCombiner::isAlias
// and operates with MachineMemOperand offset with some important
// assumptions:
@@ -1698,22 +1693,53 @@
// - There should never be any negative offsets here.
//
// FIXME: Modify API to hide this math from "user"
- // FIXME: Even before we go to AA we can reason locally about some
+ // Even before we go to AA we can reason locally about some
// memory objects. It can save compile time, and possibly catch some
// corner cases not currently covered.
- assert((MMOa->getOffset() >= 0) && "Negative MachineMemOperand offset");
- assert((MMOb->getOffset() >= 0) && "Negative MachineMemOperand offset");
+ int64_t OffsetA = MMOa->getOffset();
+ int64_t OffsetB = MMOb->getOffset();
- int64_t MinOffset = std::min(MMOa->getOffset(), MMOb->getOffset());
- int64_t Overlapa = MMOa->getSize() + MMOa->getOffset() - MinOffset;
- int64_t Overlapb = MMOb->getSize() + MMOb->getOffset() - MinOffset;
+ int64_t MinOffset = std::min(OffsetA, OffsetB);
+ int64_t WidthA = MMOa->getSize();
+ int64_t WidthB = MMOb->getSize();
+ const Value *ValA = MMOa->getValue();
+ const Value *ValB = MMOb->getValue();
+ bool SameVal = (ValA && ValB && (ValA == ValB));
+ if (!SameVal) {
+ const PseudoSourceValue *PSVa = MMOa->getPseudoValue();
+ const PseudoSourceValue *PSVb = MMOb->getPseudoValue();
+ if (PSVa && ValB && !PSVa->mayAlias(&MFI))
+ return false;
+ if (PSVb && ValA && !PSVb->mayAlias(&MFI))
+ return false;
+ if (PSVa && PSVb && (PSVa == PSVb))
+ SameVal = true;
+ }
- AliasResult AAResult =
- AA->alias(MemoryLocation(MMOa->getValue(), Overlapa,
- UseTBAA ? MMOa->getAAInfo() : AAMDNodes()),
- MemoryLocation(MMOb->getValue(), Overlapb,
- UseTBAA ? MMOb->getAAInfo() : AAMDNodes()));
+ if (SameVal) {
+ int64_t MaxOffset = std::max(OffsetA, OffsetB);
+ int64_t LowWidth = (MinOffset == OffsetA) ? WidthA : WidthB;
+ return (MinOffset + LowWidth > MaxOffset);
+ }
+
+ if (!AA)
+ return true;
+
+ if (!ValA || !ValB)
+ return true;
+
+ assert((OffsetA >= 0) && "Negative MachineMemOperand offset");
+ assert((OffsetB >= 0) && "Negative MachineMemOperand offset");
+
+ int64_t Overlapa = WidthA + OffsetA - MinOffset;
+ int64_t Overlapb = WidthB + OffsetB - MinOffset;
+
+ AliasResult AAResult = AA->alias(
+ MemoryLocation(ValA, Overlapa,
+ UseTBAA ? MMOa->getAAInfo() : AAMDNodes()),
+ MemoryLocation(ValB, Overlapb,
+ UseTBAA ? MMOb->getAAInfo() : AAMDNodes()));
return (AAResult != NoAlias);
}