diff --git a/llvm/lib/Target/X86/X86FixupBWInsts.cpp b/llvm/lib/Target/X86/X86FixupBWInsts.cpp index 3583980ff4f3..c28746f96439 100644 --- a/llvm/lib/Target/X86/X86FixupBWInsts.cpp +++ b/llvm/lib/Target/X86/X86FixupBWInsts.cpp @@ -95,10 +95,9 @@ class FixupBWInstPass : public MachineFunctionPass { // Change the MachineInstr \p MI into an eqivalent 32 bit instruction if // possible. Return the replacement instruction if OK, return nullptr - // otherwise. Set WasCandidate to true or false depending on whether the - // MI was a candidate for this sort of transformation. - MachineInstr *tryReplaceInstr(MachineInstr *MI, MachineBasicBlock &MBB, - bool &WasCandidate) const; + // otherwise. + MachineInstr *tryReplaceInstr(MachineInstr *MI, MachineBasicBlock &MBB) const; + public: static char ID; @@ -269,12 +268,8 @@ MachineInstr *FixupBWInstPass::tryReplaceCopy(MachineInstr *MI) const { return MIB; } -MachineInstr *FixupBWInstPass::tryReplaceInstr( - MachineInstr *MI, MachineBasicBlock &MBB, - bool &WasCandidate) const { - MachineInstr *NewMI = nullptr; - WasCandidate = false; - +MachineInstr *FixupBWInstPass::tryReplaceInstr(MachineInstr *MI, + MachineBasicBlock &MBB) const { // See if this is an instruction of the type we are currently looking for. switch (MI->getOpcode()) { @@ -282,12 +277,9 @@ MachineInstr *FixupBWInstPass::tryReplaceInstr( // Only replace 8 bit loads with the zero extending versions if // in an inner most loop and not optimizing for size. This takes // an extra byte to encode, and provides limited performance upside. - if (MachineLoop *ML = MLI->getLoopFor(&MBB)) { - if (ML->begin() == ML->end() && !OptForSize) { - NewMI = tryReplaceLoad(X86::MOVZX32rm8, MI); - WasCandidate = true; - } - } + if (MachineLoop *ML = MLI->getLoopFor(&MBB)) + if (ML->begin() == ML->end() && !OptForSize) + return tryReplaceLoad(X86::MOVZX32rm8, MI); break; case X86::MOV16rm: @@ -295,9 +287,7 @@ MachineInstr *FixupBWInstPass::tryReplaceInstr( // Code size is the same, and there is sometimes a perf advantage // from eliminating a false dependence on the upper portion of // the register. - NewMI = tryReplaceLoad(X86::MOVZX32rm16, MI); - WasCandidate = true; - break; + return tryReplaceLoad(X86::MOVZX32rm16, MI); case X86::MOV8rr: case X86::MOV16rr: @@ -305,16 +295,14 @@ MachineInstr *FixupBWInstPass::tryReplaceInstr( // Code size is either less (16) or equal (8), and there is sometimes a // perf advantage from eliminating a false dependence on the upper portion // of the register. - NewMI = tryReplaceCopy(MI); - WasCandidate = true; - break; + return tryReplaceCopy(MI); default: // nothing to do here. break; } - return NewMI; + return nullptr; } void FixupBWInstPass::processBasicBlock(MachineFunction &MF, @@ -338,18 +326,11 @@ void FixupBWInstPass::processBasicBlock(MachineFunction &MF, // We run after PEI, so we need to AddPristinesAndCSRs. LiveRegs.addLiveOuts(MBB); - bool WasCandidate = false; - for (auto I = MBB.rbegin(); I != MBB.rend(); ++I) { MachineInstr *MI = &*I; - MachineInstr *NewMI = tryReplaceInstr(MI, MBB, WasCandidate); - - // Add this to replacements if it was a candidate, even if NewMI is - // nullptr. We will revisit that in a bit. - if (WasCandidate) { + if (MachineInstr *NewMI = tryReplaceInstr(MI, MBB)) MIReplacements.push_back(std::make_pair(MI, NewMI)); - } // We're done with this instruction, update liveness for the next one. LiveRegs.stepBackward(*MI); @@ -359,9 +340,7 @@ void FixupBWInstPass::processBasicBlock(MachineFunction &MF, MachineInstr *MI = MIReplacements.back().first; MachineInstr *NewMI = MIReplacements.back().second; MIReplacements.pop_back(); - if (NewMI) { - MBB.insert(MI, NewMI); - MBB.erase(MI); - } + MBB.insert(MI, NewMI); + MBB.erase(MI); } }