Am Mo., 21. Okt. 2019 um 16:01 Uhr schrieb Jordan Rupprecht via
cfe-commits <cfe-commits@lists.llvm.org>:
> There's also a curious failure caused by this patch (confirmed passing
> @r374287, failing @r374288):
It's a warning, not a failure.
> $ cat /tmp/vectorize.cc
> void a() {
> #pragma clang loop vectorize(disable)
> for (;;)
> ;
> }
>
> $ clang++ -Werror -O3 -c /tmp/vectorize.cc
> /tmp/vectorize.cc:1:6: error: loop not interleaved: the optimizer was unable
> to perform the requested transformation; the transformation might be disabled
> or specified as part of an unsupported transformation ordering
> [-Werror,-Wpass-failed=transform-warning]
> void a() {
>
> I don't understand this warning -- there is no requested transformation; in
> fact, we've explicitly specified that vectorization *should* be disabled.
https://reviews.llvm.org/D66290
generates the following metadata for #pragma clang loop vectorize(disable):
!3 = distinct !{!3, !4, !5}
!4 = !{!"llvm.loop.vectorize.enable", i1 true}
!5 = !{!"llvm.loop.vectorize.width", i32 1}
which is interpreted as "enable LoopVectorize, but only the interleave
part" by LoopVectorize and WarnMissedTransformations.
The tests in D66290 missed that because the regex may matche multiple MDNodes:
// CHECK: ![[LOOP_5]] = distinct !{![[LOOP_5]],
![[UNROLL_DISABLE:.*]], ![[DISTRIBUTE_DISABLE:.*]], ![[WIDTH_1:.*]]}
The additional "llvm.loop.vectorize.enable" is generated by:
if (Attrs.VectorizeWidth > 0) {
// This implies vectorize.enable = true, but only add it when it is not
// already enabled.
if (Attrs.VectorizeEnable != LoopAttributes::Enable)
Attr.VectorizeWidth is set by the vectorize(disable) LoopHint:
case LoopHintAttr::Disable:
switch (Option) {
case LoopHintAttr::Vectorize:
// Disable vectorization by specifying a width of 1.
setVectorizeWidth(1);
Michael
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