Anti-dependency breaking needs to be careful regarding instructions with
multiple register definitions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92864 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CriticalAntiDepBreaker.cpp b/lib/CodeGen/CriticalAntiDepBreaker.cpp
index e5d68a6..056e2d5 100644
--- a/lib/CodeGen/CriticalAntiDepBreaker.cpp
+++ b/lib/CodeGen/CriticalAntiDepBreaker.cpp
@@ -288,7 +288,8 @@
}
unsigned
-CriticalAntiDepBreaker::findSuitableFreeRegister(unsigned AntiDepReg,
+CriticalAntiDepBreaker::findSuitableFreeRegister(MachineInstr *MI,
+ unsigned AntiDepReg,
unsigned LastNewReg,
const TargetRegisterClass *RC)
{
@@ -301,6 +302,10 @@
// an anti-dependence with this AntiDepReg, because that would
// re-introduce that anti-dependence.
if (NewReg == LastNewReg) continue;
+ // If the instruction already has a def of the NewReg, it's not suitable.
+ // For example, Instruction with multiple definitions can result in this
+ // condition.
+ if (MI->modifiesRegister(NewReg, TRI)) continue;
// If NewReg is dead and NewReg's most recent def is not before
// AntiDepReg's kill, it's safe to replace AntiDepReg with NewReg.
assert(((KillIndices[AntiDepReg] == ~0u) != (DefIndices[AntiDepReg] == ~0u))
@@ -496,7 +501,7 @@
// TODO: Instead of picking the first free register, consider which might
// be the best.
if (AntiDepReg != 0) {
- if (unsigned NewReg = findSuitableFreeRegister(AntiDepReg,
+ if (unsigned NewReg = findSuitableFreeRegister(MI, AntiDepReg,
LastNewReg[AntiDepReg],
RC)) {
DEBUG(dbgs() << "Breaking anti-dependence edge on "