Add "mayHaveSideEffects" and "neverHasSideEffects" flags to some instructions. I
based what flag to set on whether it was already marked as
"isRematerializable". If there was a further check to determine if it's "really"
rematerializable, then I marked it as "mayHaveSideEffects" and created a check
in the X86 back-end similar to the remat one.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45132 91177308-0d34-0410-b5e6-96231b3b80d8
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 @@
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) {