diff options
Diffstat (limited to 'lib/Target/X86/X86InstrInfo.cpp')
| -rw-r--r-- | lib/Target/X86/X86InstrInfo.cpp | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/lib/Target/X86/X86InstrInfo.cpp b/lib/Target/X86/X86InstrInfo.cpp index 69493bc207..89a57b53f3 100644 --- a/lib/Target/X86/X86InstrInfo.cpp +++ b/lib/Target/X86/X86InstrInfo.cpp @@ -3221,12 +3221,15 @@ optimizeCompareInstr(MachineInstr *CmpInstr, unsigned SrcReg, unsigned SrcReg2, MachineBasicBlock::iterator E = CmpInstr->getParent()->end(); for (++I; I != E; ++I) { const MachineInstr &Instr = *I; - if (Instr.modifiesRegister(X86::EFLAGS, TRI)) { + bool ModifyEFLAGS = Instr.modifiesRegister(X86::EFLAGS, TRI); + bool UseEFLAGS = Instr.readsRegister(X86::EFLAGS, TRI); + // We should check the usage if this instruction uses and updates EFLAGS. + if (!UseEFLAGS && ModifyEFLAGS) { // It is safe to remove CmpInstr if EFLAGS is updated again. IsSafe = true; break; } - if (!Instr.readsRegister(X86::EFLAGS, TRI)) + if (!UseEFLAGS && !ModifyEFLAGS) continue; // EFLAGS is used by this instruction. @@ -3281,7 +3284,8 @@ optimizeCompareInstr(MachineInstr *CmpInstr, unsigned SrcReg, unsigned SrcReg2, // instructions will be modified. OpsToUpdate.push_back(std::make_pair(&*I, NewOpc)); } - if (Instr.killsRegister(X86::EFLAGS, TRI)) { + if (ModifyEFLAGS || Instr.killsRegister(X86::EFLAGS, TRI)) { + // It is safe to remove CmpInstr if EFLAGS is updated again or killed. IsSafe = true; break; } |