LSR: Fix another corner case in expansion of postinc users.
Fixes PR11571: Instruction does not dominate all uses
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146950 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ScalarEvolutionExpander.cpp b/lib/Analysis/ScalarEvolutionExpander.cpp
index f3cf549..5f83914 100644
--- a/lib/Analysis/ScalarEvolutionExpander.cpp
+++ b/lib/Analysis/ScalarEvolutionExpander.cpp
@@ -1019,6 +1019,16 @@
BasicBlock *SaveInsertBB = Builder.GetInsertBlock();
BasicBlock::iterator SaveInsertPt = Builder.GetInsertPoint();
+ // Another AddRec may need to be recursively expanded below. For example, if
+ // this AddRec is quadratic, the StepV may itself be an AddRec in this
+ // loop. Remove this loop from the PostIncLoops set before expanding such
+ // AddRecs. Otherwise, we cannot find a valid position for the step
+ // (i.e. StepV can never dominate its loop header). Ideally, we could do
+ // SavedIncLoops.swap(PostIncLoops), but we generally have a single element,
+ // so it's not worth implementing SmallPtrSet::swap.
+ PostIncLoopSet SavedPostIncLoops = PostIncLoops;
+ PostIncLoops.clear();
+
// Expand code for the start value.
Value *StartV = expandCodeFor(Normalized->getStart(), ExpandTy,
L->getHeader()->begin());
@@ -1073,6 +1083,10 @@
if (SaveInsertBB)
restoreInsertPoint(SaveInsertBB, SaveInsertPt);
+ // After expanding subexpressions, restore the PostIncLoops set so the caller
+ // can ensure that IVIncrement dominates the current uses.
+ PostIncLoops = SavedPostIncLoops;
+
// Remember this PHI, even in post-inc mode.
InsertedValues.insert(PN);