Do not extend extension results beyond the use of a PHI instruction at the start of a use block. A PHI use is expected to kill its source values.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93895 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/OptimizeExts.cpp b/lib/CodeGen/OptimizeExts.cpp
index 625ff89..096f9d4 100644
--- a/lib/CodeGen/OptimizeExts.cpp
+++ b/lib/CodeGen/OptimizeExts.cpp
@@ -143,11 +143,23 @@
// Now replace all uses.
if (!Uses.empty()) {
+ SmallPtrSet<MachineBasicBlock*, 4> PHIBBs;
+ // Look for PHI uses of the extended result, we don't want to extend the
+ // liveness of a PHI input. It breaks all kinds of assumptions down
+ // stream. A PHI use is expected to be the kill of its source values.
+ UI = MRI->use_begin(DstReg);
+ for (MachineRegisterInfo::use_iterator UE = MRI->use_end(); UI != UE;
+ ++UI)
+ if (UI->getOpcode() == TargetInstrInfo::PHI)
+ PHIBBs.insert(UI->getParent());
+
const TargetRegisterClass *RC = MRI->getRegClass(SrcReg);
for (unsigned i = 0, e = Uses.size(); i != e; ++i) {
MachineOperand *UseMO = Uses[i];
MachineInstr *UseMI = UseMO->getParent();
MachineBasicBlock *UseMBB = UseMI->getParent();
+ if (PHIBBs.count(UseMBB))
+ continue;
unsigned NewVR = MRI->createVirtualRegister(RC);
BuildMI(*UseMBB, UseMI, UseMI->getDebugLoc(),
TII->get(TargetInstrInfo::EXTRACT_SUBREG), NewVR)