diff options
Diffstat (limited to 'lib/Target/X86/X86InstrInfo.cpp')
| -rw-r--r-- | lib/Target/X86/X86InstrInfo.cpp | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/lib/Target/X86/X86InstrInfo.cpp b/lib/Target/X86/X86InstrInfo.cpp index 9d5e637..d6d146f 100644 --- a/lib/Target/X86/X86InstrInfo.cpp +++ b/lib/Target/X86/X86InstrInfo.cpp @@ -144,6 +144,40 @@ bool X86InstrInfo::isReallyTriviallyReMaterializable(MachineInstr *MI) const { return true; } +/// isReallySideEffectFree - If the M_MAY_HAVE_SIDE_EFFECTS flag is set, this +/// method is called to determine if the specific instance of this instruction +/// has side effects. This is useful in cases of instructions, like loads, which +/// generally always have side effects. A load from a constant pool doesn't have +/// side effects, though. So we need to differentiate it from the general case. +bool X86InstrInfo::isReallySideEffectFree(MachineInstr *MI) const { + switch (MI->getOpcode()) { + default: break; + case X86::MOV8rm: + case X86::MOV16rm: + case X86::MOV16_rm: + case X86::MOV32rm: + case X86::MOV32_rm: + case X86::MOV64rm: + case X86::LD_Fp64m: + case X86::MOVSSrm: + case X86::MOVSDrm: + case X86::MOVAPSrm: + case X86::MOVAPDrm: + case X86::MMX_MOVD64rm: + case X86::MMX_MOVQ64rm: + // Loads from constant pools have no side effects + return MI->getOperand(1).isRegister() && MI->getOperand(2).isImmediate() && + MI->getOperand(3).isRegister() && MI->getOperand(4).isConstantPoolIndex() && + MI->getOperand(1).getReg() == 0 && + MI->getOperand(2).getImmedValue() == 1 && + MI->getOperand(3).getReg() == 0; + } + + // All other instances of these instructions are presumed to have side + // effects. + return false; +} + /// hasLiveCondCodeDef - True if MI has a condition code def, e.g. EFLAGS, that /// is not marked dead. static bool hasLiveCondCodeDef(MachineInstr *MI) { |