We don't need to try to coalesce input vregs that are the same as the output vreg.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54422 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/StrongPHIElimination.cpp b/lib/CodeGen/StrongPHIElimination.cpp
index b276e80..11b8ca3 100644
--- a/lib/CodeGen/StrongPHIElimination.cpp
+++ b/lib/CodeGen/StrongPHIElimination.cpp
@@ -421,6 +421,7 @@
while (P != MBB->end() && P->getOpcode() == TargetInstrInfo::PHI) {
unsigned DestReg = P->getOperand(0).getReg();
+
// Don't both doing PHI elimination for dead PHI's.
if (P->registerDefIsDead(DestReg)) {
++P;
@@ -442,6 +443,12 @@
// Iterate over the operands of the PHI node
for (int i = P->getNumOperands() - 1; i >= 2; i-=2) {
unsigned SrcReg = P->getOperand(i-1).getReg();
+
+ // Don't need to try to coalesce a register with itself.
+ if (SrcReg == DestReg) {
+ ProcessedNames.insert(SrcReg);
+ continue;
+ }
// Check for trivial interferences via liveness information, allowing us
// to avoid extra work later. Any registers that interfere cannot both