LSR fix: broaden the check for loop preheaders.
It's becoming clear that LoopSimplify needs to unconditionally create loop preheaders. But that is a bigger fix. For now, continuing to hack LSR.
Fixes rdar://10701050 "Cannot split an edge from an IndirectBrInst" assert.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148288 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 85f1389..baf5669 100644
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -4518,11 +4518,19 @@
if (!L->isLoopSimplifyForm())
return;
- // All outer loops must have preheaders, or SCEVExpander may not be able to
- // materialize an AddRecExpr whose Start is an outer AddRecExpr.
- for (const Loop *OuterLoop = L; (OuterLoop = OuterLoop->getParentLoop());) {
- if (!OuterLoop->getLoopPreheader())
- return;
+ // All dominating loops must have preheaders, or SCEVExpander may not be able
+ // to materialize an AddRecExpr whose Start is an outer AddRecExpr.
+ //
+ // FIXME: This is a little absurd. I think LoopSimplify should be taught
+ // to create a preheader under any circumstance.
+ for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader());
+ Rung; Rung = Rung->getIDom()) {
+ BasicBlock *BB = Rung->getBlock();
+ const Loop *DomLoop = LI.getLoopFor(BB);
+ if (DomLoop && DomLoop->getHeader() == BB) {
+ if (!DomLoop->getLoopPreheader())
+ return;
+ }
}
// If there's no interesting work to be done, bail early.
if (IU.empty()) return;