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[SCEVExpander] Fix a failed cast<> assertion 

SCEVExpander::replaceCongruentIVs assumes the backedge value of an
SCEV-analysable PHI to always be an instruction, when this is not
necessarily true.  For now address this by bailing out of the
optimization if the backedge value of the PHI is a non-Instruction.

llvm-svn: 269213
This commit is contained in:
Sanjoy Das 2016-05-11 17:41:41 +00:00
parent abb7b93eb9
commit 4e8c80382f
2 changed files with 116 additions and 42 deletions
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88
llvm/lib/Analysis/ScalarEvolutionExpander.cpp
View File

@ -1794,51 +1794,55 @@ unsigned SCEVExpander::replaceCongruentIVs(Loop *L, const DominatorTree *DT,
continue;
if (BasicBlock *LatchBlock = L->getLoopLatch()) {
Instruction *OrigInc =
cast<Instruction>(OrigPhiRef->getIncomingValueForBlock(LatchBlock));
Instruction *OrigInc = dyn_cast<Instruction>(
OrigPhiRef->getIncomingValueForBlock(LatchBlock));
Instruction *IsomorphicInc =
cast<Instruction>(Phi->getIncomingValueForBlock(LatchBlock));
dyn_cast<Instruction>(Phi->getIncomingValueForBlock(LatchBlock));
// If this phi has the same width but is more canonical, replace the
// original with it. As part of the "more canonical" determination,
// respect a prior decision to use an IV chain.
if (OrigPhiRef->getType() == Phi->getType() &&
!(ChainedPhis.count(Phi) ||
isExpandedAddRecExprPHI(OrigPhiRef, OrigInc, L)) &&
(ChainedPhis.count(Phi) ||
isExpandedAddRecExprPHI(Phi, IsomorphicInc, L))) {
std::swap(OrigPhiRef, Phi);
std::swap(OrigInc, IsomorphicInc);
}
// Replacing the congruent phi is sufficient because acyclic redundancy
// elimination, CSE/GVN, should handle the rest. However, once SCEV proves
// that a phi is congruent, it's often the head of an IV user cycle that
// is isomorphic with the original phi. It's worth eagerly cleaning up the
// common case of a single IV increment so that DeleteDeadPHIs can remove
// cycles that had postinc uses.
const SCEV *TruncExpr = SE.getTruncateOrNoop(SE.getSCEV(OrigInc),
IsomorphicInc->getType());
if (OrigInc != IsomorphicInc && TruncExpr == SE.getSCEV(IsomorphicInc) &&
SE.LI.replacementPreservesLCSSAForm(IsomorphicInc, OrigInc) &&
hoistIVInc(OrigInc, IsomorphicInc)) {
DEBUG_WITH_TYPE(DebugType,
dbgs() << "INDVARS: Eliminated congruent iv.inc: "
<< *IsomorphicInc << '\n');
Value *NewInc = OrigInc;
if (OrigInc->getType() != IsomorphicInc->getType()) {
Instruction *IP = nullptr;
if (PHINode *PN = dyn_cast<PHINode>(OrigInc))
IP = &*PN->getParent()->getFirstInsertionPt();
else
IP = OrigInc->getNextNode();
IRBuilder<> Builder(IP);
Builder.SetCurrentDebugLocation(IsomorphicInc->getDebugLoc());
NewInc = Builder.
CreateTruncOrBitCast(OrigInc, IsomorphicInc->getType(), IVName);
if (OrigInc && IsomorphicInc) {
// If this phi has the same width but is more canonical, replace the
// original with it. As part of the "more canonical" determination,
// respect a prior decision to use an IV chain.
if (OrigPhiRef->getType() == Phi->getType() &&
!(ChainedPhis.count(Phi) ||
isExpandedAddRecExprPHI(OrigPhiRef, OrigInc, L)) &&
(ChainedPhis.count(Phi) ||
isExpandedAddRecExprPHI(Phi, IsomorphicInc, L))) {
std::swap(OrigPhiRef, Phi);
std::swap(OrigInc, IsomorphicInc);
}
// Replacing the congruent phi is sufficient because acyclic
// redundancy elimination, CSE/GVN, should handle the
// rest. However, once SCEV proves that a phi is congruent,
// it's often the head of an IV user cycle that is isomorphic
// with the original phi. It's worth eagerly cleaning up the
// common case of a single IV increment so that DeleteDeadPHIs
// can remove cycles that had postinc uses.
const SCEV *TruncExpr =
SE.getTruncateOrNoop(SE.getSCEV(OrigInc), IsomorphicInc->getType());
if (OrigInc != IsomorphicInc &&
TruncExpr == SE.getSCEV(IsomorphicInc) &&
SE.LI.replacementPreservesLCSSAForm(IsomorphicInc, OrigInc) &&
hoistIVInc(OrigInc, IsomorphicInc)) {
DEBUG_WITH_TYPE(DebugType,
dbgs() << "INDVARS: Eliminated congruent iv.inc: "
<< *IsomorphicInc << '\n');
Value *NewInc = OrigInc;
if (OrigInc->getType() != IsomorphicInc->getType()) {
Instruction *IP = nullptr;
if (PHINode *PN = dyn_cast<PHINode>(OrigInc))
IP = &*PN->getParent()->getFirstInsertionPt();
else
IP = OrigInc->getNextNode();
IRBuilder<> Builder(IP);
Builder.SetCurrentDebugLocation(IsomorphicInc->getDebugLoc());
NewInc = Builder.CreateTruncOrBitCast(
OrigInc, IsomorphicInc->getType(), IVName);
}
IsomorphicInc->replaceAllUsesWith(NewInc);
DeadInsts.emplace_back(IsomorphicInc);
}
IsomorphicInc->replaceAllUsesWith(NewInc);
DeadInsts.emplace_back(IsomorphicInc);
}
}
DEBUG_WITH_TYPE(DebugType, dbgs() << "INDVARS: Eliminated congruent iv: "

70
llvm/test/Analysis/ScalarEvolution/expander-replace-congruent-ivs.ll
View File

@ -39,3 +39,73 @@ loop_1:
leave:
ret void
}
; @ReplaceArg_0 and @ReplaceArg_1 used to trigger a failed cast<>
; assertion in SCEVExpander.
define void @ReplaceArg_0(i32 %val) {
; CHECK-LABEL: @ReplaceArg_0(
entry:
br i1 undef, label %loop_0.cond, label %for.body.us
for.body.us:
br label %loop_0.cond
loop_0.cond:
br i1 true, label %loop_0.ph, label %loop_1.ph
loop_0.ph:
br label %loop_0
loop_1.exit:
br label %loop_1.ph
loop_1.ph:
%c.lcssa = phi i32 [ 0, %loop_0.cond ], [ %val, %loop_1.exit ]
br label %loop_1
loop_0:
br i1 undef, label %loop_0, label %loop_1.exit
loop_1:
%d.1 = phi i32 [ %c.lcssa, %loop_1 ], [ %val, %loop_1.ph ]
%t.1 = phi i32 [ %val, %loop_1 ], [ %c.lcssa, %loop_1.ph ]
br i1 undef, label %leave, label %loop_1
leave:
ret void
}
define void @ReplaceArg_1(i32 %val) {
; CHECK-LABEL: @ReplaceArg_1(
entry:
br i1 undef, label %loop_0.cond, label %for.body.us
for.body.us:
br label %loop_0.cond
loop_0.cond:
br i1 true, label %loop_0.ph, label %loop_1.ph
loop_0.ph:
br label %loop_0
loop_1.exit:
br label %loop_1.ph
loop_1.ph:
%c.lcssa = phi i32 [ 0, %loop_0.cond ], [ %val, %loop_1.exit ]
br label %loop_1
loop_0:
br i1 undef, label %loop_0, label %loop_1.exit
loop_1:
%t.1 = phi i32 [ %val, %loop_1 ], [ %c.lcssa, %loop_1.ph ]
%d.1 = phi i32 [ %c.lcssa, %loop_1 ], [ %val, %loop_1.ph ]
br i1 undef, label %leave, label %loop_1
leave:
ret void
}