[Reassociate] Avoid iterator invalidation when negating value.

Differential Revision: https://reviews.llvm.org/D23464
PR28367

llvm-svn: 278928

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index b930a8fb7e9..5b3e7c50e50 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -842,6 +842,13 @@ static Value *NegateValue(Value *V, Instruction *BI,
     if (TheNeg->getParent()->getParent() != BI->getParent()->getParent())
       continue;
 
+    // Don't move the negate if it's in the block we're currently optimizing as
+    // this may invalidate our iterator.
+    // FIXME: We should find a more robust solution as we're missing local CSE
+    // opportunities because of this constraint.
+    if (TheNeg->getParent() == BI->getParent())
+      continue;
+
     BasicBlock::iterator InsertPt;
     if (Instruction *InstInput = dyn_cast<Instruction>(V)) {
       if (InvokeInst *II = dyn_cast<InvokeInst>(InstInput)) {
@@ -1863,6 +1870,8 @@ void ReassociatePass::RecursivelyEraseDeadInsts(
 /// Zap the given instruction, adding interesting operands to the work list.
 void ReassociatePass::EraseInst(Instruction *I) {
   assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!");
+  DEBUG(dbgs() << "Erasing dead inst: "; I->dump());
+
   SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
   // Erase the dead instruction.
   ValueRankMap.erase(I);