Fix a logic error. An instruction that has a live physical register def cannot be CSE'ed, but it *can* be used to replace a common subexpression.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97688 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineCSE.cpp b/lib/CodeGen/MachineCSE.cpp
index ea11bfb..d542cc9 100644
--- a/lib/CodeGen/MachineCSE.cpp
+++ b/lib/CodeGen/MachineCSE.cpp
@@ -128,8 +128,6 @@
if (TII->isMoveInstr(*MI, SrcReg, DstReg, SrcSubIdx, DstSubIdx) ||
MI->isExtractSubreg() || MI->isInsertSubreg() || MI->isSubregToReg())
continue;
- if (hasLivePhysRegDefUse(MI))
- continue;
bool FoundCSE = VNT.count(MI);
if (!FoundCSE) {
@@ -138,6 +136,11 @@
FoundCSE = VNT.count(MI);
}
+ // If the instruction defines a physical register and the value *may* be
+ // used, then it's not safe to replace it with a common subexpression.
+ if (FoundCSE && hasLivePhysRegDefUse(MI))
+ FoundCSE = false;
+
if (!FoundCSE) {
VNT.insert(MI, CurrVN++);
Exps.push_back(MI);