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LoopVectorizer: Fix an endless loop in the code that looks for reductions.

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The bug was in the code that detects PHIs in if-then-else block sequence.

PR14701.

llvm-svn: 171008
This commit is contained in:
Nadav Rotem 2012-12-24 01:22:06 +00:00
parent 94f3dc5280
commit 309d628c4f
2 changed files with 52 additions and 7 deletions
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15
lib/Transforms/Vectorize/LoopVectorize.cpp
View File

@ -1737,10 +1737,9 @@ bool LoopVectorizationLegality::AddReductionVar(PHINode *Phi,
Instruction *ExitInstruction = 0;
// Iter is our iterator. We start with the PHI node and scan for all of the
// users of this instruction. All users must be instructions which can be
// users of this instruction. All users must be instructions that can be
// used as reduction variables (such as ADD). We may have a single
// out-of-block user. They cycle must end with the original PHI.
// Also, we can't have multiple block-local users.
// out-of-block user. The cycle must end with the original PHI.
Instruction *Iter = Phi;
while (true) {
// If the instruction has no users then this is a broken
@ -1752,9 +1751,9 @@ bool LoopVectorizationLegality::AddReductionVar(PHINode *Phi,
if (!isReductionInstr(Iter, Kind))
return false;
// Did we find a user inside this block ?
// Did we find a user inside this loop already ?
bool FoundInBlockUser = false;
// Did we reach the initial PHI node ?
// Did we reach the initial PHI node already ?
bool FoundStartPHI = false;
// For each of the *users* of iter.
@ -1779,8 +1778,10 @@ bool LoopVectorizationLegality::AddReductionVar(PHINode *Phi,
// We allow in-loop PHINodes which are not the original reduction PHI
// node. If this PHI is the only user of Iter (happens in IF w/ no ELSE
// structure) then don't skip this PHI.
if (isa<PHINode>(U) && U->getParent() != TheLoop->getHeader() &&
TheLoop->contains(U) && Iter->getNumUses() > 1)
if (isa<PHINode>(Iter) && isa<PHINode>(U) &&
U->getParent() != TheLoop->getHeader() &&
TheLoop->contains(U) &&
Iter->getNumUses() > 1)
continue;
// We can't have multiple inside users.

44
test/Transforms/LoopVectorize/2012-10-20-infloop.ll
View File

@ -25,3 +25,47 @@ for.body: ; preds = %for.body, %entry
for.end: ; preds = %for.body
unreachable
}
;PR14701
define void @start_model_rare() nounwind uwtable ssp {
entry:
br i1 undef, label %return, label %if.end
if.end: ; preds = %entry
br i1 undef, label %cond.false, label %cond.true
cond.true: ; preds = %if.end
unreachable
cond.false: ; preds = %if.end
br i1 undef, label %cond.false28, label %cond.true20
cond.true20: ; preds = %cond.false
unreachable
cond.false28: ; preds = %cond.false
br label %for.body40
for.body40: ; preds = %for.inc50, %cond.false28
%indvars.iv123 = phi i64 [ 3, %cond.false28 ], [ %indvars.iv.next124, %for.inc50 ]
%step.0121 = phi i32 [ 1, %cond.false28 ], [ %step.1, %for.inc50 ]
br i1 undef, label %if.then46, label %for.inc50
if.then46: ; preds = %for.body40
%inc47 = add nsw i32 %step.0121, 1
br label %for.inc50
for.inc50: ; preds = %if.then46, %for.body40
%k.1 = phi i32 [ undef, %for.body40 ], [ %inc47, %if.then46 ]
%step.1 = phi i32 [ %step.0121, %for.body40 ], [ %inc47, %if.then46 ]
%indvars.iv.next124 = add i64 %indvars.iv123, 1
%lftr.wideiv = trunc i64 %indvars.iv.next124 to i32
%exitcond = icmp eq i32 %lftr.wideiv, 256
br i1 %exitcond, label %for.end52, label %for.body40
for.end52: ; preds = %for.inc50
unreachable
return: ; preds = %entry
ret void
}