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Mark all uses as <undef> when joining a copy.

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This way, shrinkToUses() will ignore the instruction that is about to be
deleted, and we avoid leaving invalid live ranges that SplitKit doesn't like.

Fix a misunderstanding in MachineVerifier about <def,undef> operands. The
<undef> flag is valid on def operands where it has the same meaning as <undef>
on a use operand. It only applies to sub-register defines which also read the
full register.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128642 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2011-03-31 17:23:25 +00:00
parent 48a36158ec
commit 8e53aca51a
4 changed files with 21 additions and 9 deletions
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7
lib/CodeGen/MachineVerifier.cpp
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@ -602,9 +602,7 @@ MachineVerifier::visitMachineOperand(const MachineOperand *MO, unsigned MONum) {
// Check Live Variables. // Check Live Variables.
if (MI->isDebugValue()) { if (MI->isDebugValue()) {
// Liveness checks are not valid for debug values. // Liveness checks are not valid for debug values.
} else if (MO->isUndef()) { } else if (MO->isUse() && !MO->isUndef()) {
// An <undef> doesn't refer to any register, so just skip it.
} else if (MO->isUse()) {
regsLiveInButUnused.erase(Reg); regsLiveInButUnused.erase(Reg);
bool isKill = false; bool isKill = false;
@ -675,8 +673,7 @@ MachineVerifier::visitMachineOperand(const MachineOperand *MO, unsigned MONum) {
MInfo.vregsLiveIn.insert(std::make_pair(Reg, MI)); MInfo.vregsLiveIn.insert(std::make_pair(Reg, MI));
} }
} }
} else { } else if (MO->isDef()) {
assert(MO->isDef());
// Register defined. // Register defined.
// TODO: verify that earlyclobber ops are not used. // TODO: verify that earlyclobber ops are not used.
if (MO->isDead()) if (MO->isDead())

18
lib/CodeGen/SimpleRegisterCoalescing.cpp
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@ -104,6 +104,18 @@ void SimpleRegisterCoalescing::getAnalysisUsage(AnalysisUsage &AU) const {
MachineFunctionPass::getAnalysisUsage(AU); MachineFunctionPass::getAnalysisUsage(AU);
} }
void SimpleRegisterCoalescing::markAsJoined(MachineInstr *CopyMI) {
/// Joined copies are not deleted immediately, but kept in JoinedCopies.
JoinedCopies.insert(CopyMI);
/// Mark all register operands of CopyMI as <undef> so they won't affect dead
/// code elimination.
for (MachineInstr::mop_iterator I = CopyMI->operands_begin(),
E = CopyMI->operands_end(); I != E; ++I)
if (I->isReg())
I->setIsUndef(true);
}
/// AdjustCopiesBackFrom - We found a non-trivially-coalescable copy with IntA /// AdjustCopiesBackFrom - We found a non-trivially-coalescable copy with IntA
/// being the source and IntB being the dest, thus this defines a value number /// being the source and IntB being the dest, thus this defines a value number
/// in IntB. If the source value number (in IntA) is defined by a copy from B, /// in IntB. If the source value number (in IntA) is defined by a copy from B,
@ -471,7 +483,7 @@ bool SimpleRegisterCoalescing::RemoveCopyByCommutingDef(const CoalescerPair &CP,
DEBUG(dbgs() << "\t\tnoop: " << DefIdx << '\t' << *UseMI); DEBUG(dbgs() << "\t\tnoop: " << DefIdx << '\t' << *UseMI);
assert(DVNI->def == DefIdx); assert(DVNI->def == DefIdx);
BValNo = IntB.MergeValueNumberInto(BValNo, DVNI); BValNo = IntB.MergeValueNumberInto(BValNo, DVNI);
JoinedCopies.insert(UseMI); markAsJoined(UseMI);
} }
// Extend BValNo by merging in IntA live ranges of AValNo. Val# definition // Extend BValNo by merging in IntA live ranges of AValNo. Val# definition
@ -1070,7 +1082,7 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
if (!CP.isPartial()) { if (!CP.isPartial()) {
if (AdjustCopiesBackFrom(CP, CopyMI) || if (AdjustCopiesBackFrom(CP, CopyMI) ||
RemoveCopyByCommutingDef(CP, CopyMI)) { RemoveCopyByCommutingDef(CP, CopyMI)) {
JoinedCopies.insert(CopyMI); markAsJoined(CopyMI);
DEBUG(dbgs() << "\tTrivial!\n"); DEBUG(dbgs() << "\tTrivial!\n");
return true; return true;
} }
@ -1090,7 +1102,7 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
} }
// Remember to delete the copy instruction. // Remember to delete the copy instruction.
JoinedCopies.insert(CopyMI); markAsJoined(CopyMI);
UpdateRegDefsUses(CP); UpdateRegDefsUses(CP);

3
lib/CodeGen/SimpleRegisterCoalescing.h
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@ -176,6 +176,9 @@ namespace llvm {
/// cycles Start and End or NULL if there are no uses. /// cycles Start and End or NULL if there are no uses.
MachineOperand *lastRegisterUse(SlotIndex Start, SlotIndex End, MachineOperand *lastRegisterUse(SlotIndex Start, SlotIndex End,
unsigned Reg, SlotIndex &LastUseIdx) const; unsigned Reg, SlotIndex &LastUseIdx) const;
/// markAsJoined - Remember that CopyMI has already been joined.
void markAsJoined(MachineInstr *CopyMI);
}; };
} // End llvm namespace } // End llvm namespace

2
test/CodeGen/X86/2009-04-20-LinearScanOpt.ll
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@ -1,4 +1,4 @@
; RUN: llc < %s -mtriple=x86_64-apple-darwin10.0 -relocation-model=pic -disable-fp-elim -stats |& grep asm-printer | grep 79 ; RUN: llc < %s -mtriple=x86_64-apple-darwin10.0 -relocation-model=pic -disable-fp-elim -stats |& grep asm-printer | grep 77
; rdar://6802189 ; rdar://6802189
; Test if linearscan is unfavoring registers for allocation to allow more reuse ; Test if linearscan is unfavoring registers for allocation to allow more reuse