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LoopVectorizer: Mistakenly vectorize multi reduction value users #18900

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llvmbot opened this issue Jan 18, 2014 · 2 comments
Closed

LoopVectorizer: Mistakenly vectorize multi reduction value users #18900

llvmbot opened this issue Jan 18, 2014 · 2 comments
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@llvmbot
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llvmbot commented Jan 18, 2014

Bugzilla Link 18526
Resolution FIXED
Resolved on Jan 20, 2014 00:12
Version trunk
OS All
Blocks #16805
Attachments Test case
Reporter LLVM Bugzilla Contributor
CC @hfinkel

Extended Description

t3025 and t1519 from http://llvm.org/bugs/show_bug.cgi?id=16431#c22 are misoptimized.

As described in
http://llvm.org/bugs/show_bug.cgi?id=16431#c23

"The diff tests are vectorizer bugs (look like the same bug): t3025 and t1519. They disappear with -fno-vectorize.

Furthermore,

it seems to be the loops:

for (k1 = 54; k1 > 2; k1--) {
    gp += gp - ((++n) + k1);

    // Test Loop Vectorization
    for (ju = 1; ju < 1; ++ju) {
        d5[ju] = ff[k1][k1];
    }

}

and

for (k = 2; k < 61; ++k) {
    n += n - ((f + k7) + (nf++));
    xs5[k] = 13 + 5;
    xs5[k] += nt7--;
}

We should not be vectorizing them. “gp” and “n” are not reductions. But we seem to :(."

@llvmbot
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llvmbot commented Jan 18, 2014

xref rdar://15851149

@llvmbot
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llvmbot commented Jan 19, 2014

Fixed in r199570.

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