Use Duncan's patch to delete the instructions in reverse order (minus the landingpad and terminator).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139090 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstructionCombining.cpp b/lib/Transforms/InstCombine/InstructionCombining.cpp
index 51fe2e5..f64990f 100644
--- a/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1574,15 +1574,19 @@
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
if (Visited.count(BB)) continue;
- // Delete the instructions.
- for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
- Instruction *Inst = &*I++;
- if (isa<TerminatorInst>(Inst))
- break;
+ // Delete the instructions backwards, as it has a reduced likelihood of
+ // having to update as many def-use and use-def chains.
+ Instruction *EndInst = BB->getTerminator(); // Last not to be deleted.
+ while (EndInst != BB->begin()) {
+ // Delete the next to last instruction.
+ BasicBlock::iterator I = EndInst;
+ Instruction *Inst = --I;
if (!Inst->use_empty())
Inst->replaceAllUsesWith(UndefValue::get(Inst->getType()));
- if (isa<LandingPadInst>(Inst))
+ if (isa<LandingPadInst>(Inst)) {
+ EndInst = Inst;
continue;
+ }
if (!isa<DbgInfoIntrinsic>(Inst)) {
++NumDeadInst;
MadeIRChange = true;