Fix SplitBlockPredecessors' LoopInfo updating code to handle the case
where a loop's header is being split and it has predecessors which are not
contained by the most-nested loop which contains the loop.
This fixes PR5235.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84505 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/BasicBlockUtils.cpp b/lib/Transforms/Utils/BasicBlockUtils.cpp
index 4931ab3..35907fd 100644
--- a/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -425,14 +425,26 @@
if (L) {
if (IsLoopEntry) {
- if (Loop *PredLoop = LI->getLoopFor(Preds[0])) {
- // Add the new block to the nearest enclosing loop (and not an
- // adjacent loop).
- while (PredLoop && !PredLoop->contains(BB))
- PredLoop = PredLoop->getParentLoop();
- if (PredLoop)
- PredLoop->addBasicBlockToLoop(NewBB, LI->getBase());
- }
+ // Add the new block to the nearest enclosing loop (and not an
+ // adjacent loop). To find this, examine each of the predecessors and
+ // determine which loops enclose them, and select the most-nested loop
+ // which contains the loop containing the block being split.
+ Loop *InnermostPredLoop = 0;
+ for (unsigned i = 0; i != NumPreds; ++i)
+ if (Loop *PredLoop = LI->getLoopFor(Preds[i])) {
+ // Seek a loop which actually contains the block being split (to
+ // avoid adjacent loops).
+ while (PredLoop && !PredLoop->contains(BB))
+ PredLoop = PredLoop->getParentLoop();
+ // Select the most-nested of these loops which contains the block.
+ if (PredLoop &&
+ PredLoop->contains(BB) &&
+ (!InnermostPredLoop ||
+ InnermostPredLoop->getLoopDepth() < PredLoop->getLoopDepth()))
+ InnermostPredLoop = PredLoop;
+ }
+ if (InnermostPredLoop)
+ InnermostPredLoop->addBasicBlockToLoop(NewBB, LI->getBase());
} else {
L->addBasicBlockToLoop(NewBB, LI->getBase());
if (SplitMakesNewLoopHeader)