[CodeExtractor] Fix iterator invalidation in findOrCreateBlockForHois…

…ting.

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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@317084 91177308-0d34-0410-b5e6-96231b3b80d8

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);

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