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LSR: Fix another corner case in expansion of postinc users.

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Fixes PR11571: Instruction does not dominate all uses

llvm-svn: 146950
This commit is contained in:
Andrew Trick 2011-12-20 01:42:24 +00:00
parent 8439df9506
commit a2555fd695
1 changed files with 14 additions and 0 deletions
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14
lib/Analysis/ScalarEvolutionExpander.cpp
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@ -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);