X86 Peephole: fold loads to the source register operand if possible.
Add more comments and use early returns to reduce nesting in isLoadFoldable.
Also disable folding for V_SET0 to avoid introducing a const pool entry and
a const pool load.
rdar://10554090 and rdar://11873276
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161207 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/PeepholeOptimizer.cpp b/lib/CodeGen/PeepholeOptimizer.cpp
index d9474bf..6bc7e37 100644
--- a/lib/CodeGen/PeepholeOptimizer.cpp
+++ b/lib/CodeGen/PeepholeOptimizer.cpp
@@ -391,20 +391,21 @@
/// register defined has a single use.
bool PeepholeOptimizer::isLoadFoldable(MachineInstr *MI,
unsigned &FoldAsLoadDefReg) {
- if (MI->canFoldAsLoad()) {
- const MCInstrDesc &MCID = MI->getDesc();
- if (MCID.getNumDefs() == 1) {
- unsigned Reg = MI->getOperand(0).getReg();
- // To reduce compilation time, we check MRI->hasOneUse when inserting
- // loads. It should be checked when processing uses of the load, since
- // uses can be removed during peephole.
- if (!MI->getOperand(0).getSubReg() &&
- TargetRegisterInfo::isVirtualRegister(Reg) &&
- MRI->hasOneUse(Reg)) {
- FoldAsLoadDefReg = Reg;
- return true;
- }
- }
+ if (!MI->canFoldAsLoad() || !MI->mayLoad())
+ return false;
+ const MCInstrDesc &MCID = MI->getDesc();
+ if (MCID.getNumDefs() != 1)
+ return false;
+
+ unsigned Reg = MI->getOperand(0).getReg();
+ // To reduce compilation time, we check MRI->hasOneUse when inserting
+ // loads. It should be checked when processing uses of the load, since
+ // uses can be removed during peephole.
+ if (!MI->getOperand(0).getSubReg() &&
+ TargetRegisterInfo::isVirtualRegister(Reg) &&
+ MRI->hasOneUse(Reg)) {
+ FoldAsLoadDefReg = Reg;
+ return true;
}
return false;
}