diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/CodeGen/MachineCopyPropagation.cpp | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/lib/CodeGen/MachineCopyPropagation.cpp b/lib/CodeGen/MachineCopyPropagation.cpp index 861025ca0b..c82f81b6b5 100644 --- a/lib/CodeGen/MachineCopyPropagation.cpp +++ b/lib/CodeGen/MachineCopyPropagation.cpp @@ -83,6 +83,25 @@ MachineCopyPropagation::SourceNoLongerAvailable(unsigned Reg, } } +static bool NoInterveningSideEffect(const MachineInstr *CopyMI, + const MachineInstr *MI) { + const MachineBasicBlock *MBB = CopyMI->getParent(); + if (MI->getParent() != MBB) + return false; + MachineBasicBlock::const_iterator I = CopyMI; + MachineBasicBlock::const_iterator E = MBB->end(); + MachineBasicBlock::const_iterator E2 = MI; + + ++I; + while (I != E && I != E2) { + if (I->hasUnmodeledSideEffects() || I->isCall() || + I->isTerminator()) + return false; + ++I; + } + return true; +} + bool MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) { SmallSetVector<MachineInstr*, 8> MaybeDeadCopies; // Candidates for deletion DenseMap<unsigned, MachineInstr*> AvailCopyMap; // Def -> available copies map @@ -108,6 +127,7 @@ bool MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) { MachineInstr *CopyMI = CI->second; unsigned SrcSrc = CopyMI->getOperand(1).getReg(); if (!ReservedRegs.test(Def) && + (!ReservedRegs.test(Src) || NoInterveningSideEffect(CopyMI, MI)) && (SrcSrc == Def || TRI->isSubRegister(SrcSrc, Def))) { // The two copies cancel out and the source of the first copy // hasn't been overridden, eliminate the second one. e.g. @@ -116,6 +136,12 @@ bool MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) { // %EAX<def> = COPY %ECX // => // %ECX<def> = COPY %EAX + // + // Also avoid eliminating a copy from reserved registers unless the + // definition is proven not clobbered. e.g. + // %RSP<def> = COPY %RAX + // CALL + // %RAX<def> = COPY %RSP CopyMI->getOperand(1).setIsKill(false); MI->eraseFromParent(); Changed = true; |