diff options
Diffstat (limited to 'llvm/lib/Target/X86/X86RegisterInfo.cpp')
| -rw-r--r-- | llvm/lib/Target/X86/X86RegisterInfo.cpp | 32 |
1 files changed, 31 insertions, 1 deletions
diff --git a/llvm/lib/Target/X86/X86RegisterInfo.cpp b/llvm/lib/Target/X86/X86RegisterInfo.cpp index 1b2fece6052..3e9537bd7f5 100644 --- a/llvm/lib/Target/X86/X86RegisterInfo.cpp +++ b/llvm/lib/Target/X86/X86RegisterInfo.cpp @@ -595,6 +595,35 @@ bool X86RegisterInfo::hasReservedSpillSlot(const MachineFunction &MF, llvm_unreachable("Unused function on X86. Otherwise need a test case."); } +// tryOptimizeLEAtoMOV - helper function that tries to replace a LEA instruction +// of the form 'lea (%esp), %ebx' --> 'mov %esp, %ebx'. +// TODO: In this case we should be really trying first to entirely eliminate +// this instruction which is a plain copy. +static bool tryOptimizeLEAtoMOV(MachineBasicBlock::iterator II) { + MachineInstr &MI = *II; + unsigned Opc = II->getOpcode(); + // Check if this is a LEA of the form 'lea (%esp), %ebx' + if ((Opc != X86::LEA32r && Opc != X86::LEA64r && Opc != X86::LEA64_32r) || + MI.getOperand(2).getImm() != 1 || + MI.getOperand(3).getReg() != X86::NoRegister || + MI.getOperand(4).getImm() != 0 || + MI.getOperand(5).getReg() != X86::NoRegister) + return false; + unsigned BasePtr = MI.getOperand(1).getReg(); + // In X32 mode, ensure the base-pointer is a 32-bit operand, so the LEA will + // be replaced with a 32-bit operand MOV which will zero extend the upper + // 32-bits of the super register. + if (Opc == X86::LEA64_32r) + BasePtr = getX86SubSuperRegister(BasePtr, 32); + unsigned NewDestReg = MI.getOperand(0).getReg(); + const X86InstrInfo *TII = + MI.getParent()->getParent()->getSubtarget<X86Subtarget>().getInstrInfo(); + TII->copyPhysReg(*MI.getParent(), II, MI.getDebugLoc(), NewDestReg, BasePtr, + MI.getOperand(1).isKill()); + MI.eraseFromParent(); + return true; +} + void X86RegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II, int SPAdj, unsigned FIOperandNum, @@ -669,7 +698,8 @@ X86RegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II, int Offset = FIOffset + Imm; assert((!Is64Bit || isInt<32>((long long)FIOffset + Imm)) && "Requesting 64-bit offset in 32-bit immediate!"); - MI.getOperand(FIOperandNum + 3).ChangeToImmediate(Offset); + if (Offset != 0 || !tryOptimizeLEAtoMOV(II)) + MI.getOperand(FIOperandNum + 3).ChangeToImmediate(Offset); } else { // Offset is symbolic. This is extremely rare. uint64_t Offset = FIOffset + |
