From ba3c0bc364a31bfbcc570504aae2172914b1fe9f Mon Sep 17 00:00:00 2001 From: Andrew Trick Date: Tue, 20 Dec 2011 01:42:24 +0000 Subject: [PATCH] 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 --- lib/Analysis/ScalarEvolutionExpander.cpp | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/lib/Analysis/ScalarEvolutionExpander.cpp b/lib/Analysis/ScalarEvolutionExpander.cpp index f3cf5494551..5f83914cb27 100644 --- a/lib/Analysis/ScalarEvolutionExpander.cpp +++ b/lib/Analysis/ScalarEvolutionExpander.cpp @@ -1019,6 +1019,16 @@ SCEVExpander::getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized, 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 @@ SCEVExpander::getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized, 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);