[CodeExtractor] Fix iterator invalidation in findOrCreateBlockForHoisting.

Summary: By replacing branches to CommonExitBlock, we remove the node from CommonExitBlock's predecessors, invalidating the iterator. The problem is exposed when the common exit block has multiple predecessors and needs to sink lifetime info. The modification in the test case trigger the issue. Reviewers: davidxl, davide, wmi Reviewed By: davidxl Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D39112 llvm-svn: 317084

Author: fhahn

llvm/lib/Transforms/Utils/CodeExtractor.cpp

@@ -307,7 +307,9 @@ CodeExtractor::findOrCreateBlockForHoisting(BasicBlock *CommonExitBlock) {
  BasicBlock *NewExitBlock = CommonExitBlock->splitBasicBlock(
  CommonExitBlock->getFirstNonPHI()->getIterator());
 
- for (auto *Pred : predecessors(CommonExitBlock)) {
+ for (auto PI = pred_begin(CommonExitBlock), PE = pred_end(CommonExitBlock);
+ PI != PE;) {
+ BasicBlock *Pred = *PI++;
  if (Blocks.count(Pred))
  continue;
  Pred->getTerminator()->replaceUsesOfWith(CommonExitBlock, NewExitBlock);

llvm/test/Transforms/CodeExtractor/live_shrink_hoist.ll

@@ -1,4 +1,4 @@
-; RUN: opt -S -partial-inliner -max-num-inline-blocks=2 -skip-partial-inlining-cost-analysis < %s | FileCheck %s
+; RUN: opt -S -partial-inliner -max-num-inline-blocks=3 -skip-partial-inlining-cost-analysis < %s | FileCheck %s
 ; RUN: opt -S -passes=partial-inliner -max-num-inline-blocks=2 -skip-partial-inlining-cost-analysis < %s | FileCheck %s
 
 %class.A = type { i32 }
@@ -16,6 +16,10 @@ bb:
  br i1 %tmp3, label %bb4, label %bb9
 
 bb4: ; preds = %bb
+ %foo = icmp eq i32 %tmp2, 0
+ br i1 %foo, label %bb5, label %bb9
+
+bb5: ; preds = %bb4
  call void @_ZN1A7memfuncEv(%class.A* nonnull %tmp)
  %tmp5 = getelementptr inbounds %class.A, %class.A* %tmp, i64 0, i32 0
  %tmp6 = load i32, i32* %tmp5, align 4, !tbaa !6