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LoopVectorize: Use a set to avoid longer cycles in the reduction chain too.

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Fixes PR15748.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179757 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer 2013-04-18 14:29:13 +00:00
parent d050e96133
commit 403fc14370
2 changed files with 24 additions and 8 deletions
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14
lib/Transforms/Vectorize/LoopVectorize.cpp
View File

@ -2733,7 +2733,10 @@ bool LoopVectorizationLegality::AddReductionVar(PHINode *Phi,
// used as reduction variables (such as ADD). We may have a single // used as reduction variables (such as ADD). We may have a single
// out-of-block user. The cycle must end with the original PHI. // out-of-block user. The cycle must end with the original PHI.
Instruction *Iter = Phi; Instruction *Iter = Phi;
while (true) {
// Avoid cycles in the chain.
SmallPtrSet<Instruction *, 8> VisitedInsts;
while (VisitedInsts.insert(Iter)) {
// If the instruction has no users then this is a broken // If the instruction has no users then this is a broken
// chain and can't be a reduction variable. // chain and can't be a reduction variable.
if (Iter->use_empty()) if (Iter->use_empty())
@ -2747,9 +2750,6 @@ bool LoopVectorizationLegality::AddReductionVar(PHINode *Phi,
// Is this a bin op ? // Is this a bin op ?
FoundBinOp |= !isa<PHINode>(Iter); FoundBinOp |= !isa<PHINode>(Iter);
// Remember the current instruction.
Instruction *OldIter = Iter;
// For each of the *users* of iter. // For each of the *users* of iter.
for (Value::use_iterator it = Iter->use_begin(), e = Iter->use_end(); for (Value::use_iterator it = Iter->use_begin(), e = Iter->use_end();
it != e; ++it) { it != e; ++it) {
@ -2795,10 +2795,6 @@ bool LoopVectorizationLegality::AddReductionVar(PHINode *Phi,
Iter = U; Iter = U;
} }
// If all uses were skipped this can't be a reduction variable.
if (Iter == OldIter)
return false;
// We found a reduction var if we have reached the original // We found a reduction var if we have reached the original
// phi node and we only have a single instruction with out-of-loop // phi node and we only have a single instruction with out-of-loop
// users. // users.
@ -2814,6 +2810,8 @@ bool LoopVectorizationLegality::AddReductionVar(PHINode *Phi,
return FoundBinOp && ExitInstruction; return FoundBinOp && ExitInstruction;
} }
} }
return false;
} }
bool bool

18
test/Transforms/LoopVectorize/phi-hang.ll
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@ -27,3 +27,21 @@ bb5: ; preds = %bb4, %bb1
bb11: ; preds = %bb5 bb11: ; preds = %bb5
ret void ret void
} }
; PR15748
define void @test2() {
bb:
br label %bb1
bb1: ; preds = %bb1, %bb
%tmp = phi i32 [ 0, %bb ], [ %tmp5, %bb1 ]
%tmp2 = phi i32 [ 0, %bb ], [ 1, %bb1 ]
%tmp3 = phi i32 [ 0, %bb ], [ %tmp4, %bb1 ]
%tmp4 = or i32 %tmp2, %tmp3
%tmp5 = add nsw i32 %tmp, 1
%tmp6 = icmp eq i32 %tmp5, 0
br i1 %tmp6, label %bb7, label %bb1
bb7: ; preds = %bb1
ret void
}