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Revert r372082 "[Clang] Pragma vectorize_width() implies vectorize(enable)" 

This broke the Chromium build. Consider the following code:

  float ScaleSumSamples_C(const float* src, float* dst, float scale, int width) {
    float fsum = 0.f;
    int i;
  #if defined(__clang__)
  #pragma clang loop vectorize_width(4)
  #endif
    for (i = 0; i < width; ++i) {
      float v = *src++;
      fsum += v * v;
      *dst++ = v * scale;
    }
    return fsum;
  }

Compiling at -Oz, Clang  now warns:

  $ clang++ -target x86_64 -Oz -c /tmp/a.cc
  /tmp/a.cc:1:7: warning: loop not vectorized: the optimizer was unable to
  perform the requested transformation; the transformation might be disabled or
  specified as part of an unsupported transformation ordering
  [-Wpass-failed=transform-warning]

this suggests it's not actually enabling vectorization hard enough.

At -Os it asserts instead:

  $ build.release/bin/clang++ -target x86_64 -Os -c /tmp/a.cc
  clang-10: /work/llvm.monorepo/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp:2734: void
  llvm::InnerLoopVectorizer::emitMemRuntimeChecks(llvm::Loop*, llvm::BasicBlock*): Assertion `
  !BB->getParent()->hasOptSize() && "Cannot emit memory checks when optimizing for size"' failed.

Of course neither of these are what the developer expected from the pragma.

> Specifying the vectorization width was supposed to implicitly enable
> vectorization, except that it wasn't really doing this. It was only
> setting the vectorize.width metadata, but not vectorize.enable.
>
> This should fix PR27643.
>
> Differential Revision: https://reviews.llvm.org/D66290

llvm-svn: 372225
This commit is contained in:
Hans Wennborg 2019-09-18 13:41:51 +00:00
parent 89ad7f7a1b
commit 858a1ae37d
3 changed files with 9 additions and 38 deletions
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8
clang/lib/CodeGen/CGLoopInfo.cpp
View File

@ -270,14 +270,6 @@ LoopInfo::createLoopVectorizeMetadata(const LoopAttributes &Attrs,
// Setting vectorize.width
if (Attrs.VectorizeWidth > 0) {
// This implies vectorize.enable = true, but only add it when it is not
// already enabled.
if (Attrs.VectorizeEnable != LoopAttributes::Enable)
Args.push_back(
MDNode::get(Ctx, {MDString::get(Ctx, "llvm.loop.vectorize.enable"),
ConstantAsMetadata::get(ConstantInt::get(
llvm::Type::getInt1Ty(Ctx), 1))}));
Metadata *Vals[] = {
MDString::get(Ctx, "llvm.loop.vectorize.width"),
ConstantAsMetadata::get(ConstantInt::get(llvm::Type::getInt32Ty(Ctx),

5
clang/test/CodeGenCXX/pragma-loop-predicate.cpp
View File

@ -58,6 +58,7 @@ void test5(int *List, int Length) {
List[i] = i * 2;
}
// CHECK: ![[LOOP0]] = distinct !{![[LOOP0]], !3}
// CHECK-NEXT: !3 = !{!"llvm.loop.vectorize.enable", i1 true}
@ -69,7 +70,7 @@ void test5(int *List, int Length) {
// CHECK-NEXT: ![[LOOP3]] = distinct !{![[LOOP3]], !5, !3}
// CHECK-NEXT: ![[LOOP4]] = distinct !{![[LOOP4]], !3, !10}
// CHECK-NEXT: ![[LOOP4]] = distinct !{![[LOOP4]], !10}
// CHECK-NEXT: !10 = !{!"llvm.loop.vectorize.width", i32 1}
// CHECK-NEXT: ![[LOOP5]] = distinct !{![[LOOP5]], !3, !10}
// CHECK-NEXT: ![[LOOP5]] = distinct !{![[LOOP5]], !10}

34
clang/test/CodeGenCXX/pragma-loop.cpp
View File

@ -158,41 +158,23 @@ void template_test(double *List, int Length) {
for_template_constant_expression_test<double, 2, 4, 8>(List, Length);
}
void vec_width_1(int *List, int Length) {
// CHECK-LABEL: @{{.*}}vec_width_1{{.*}}(
// CHECK: br label {{.*}}, !llvm.loop ![[LOOP_15:.*]]
#pragma clang loop vectorize(enable) vectorize_width(1)
for (int i = 0; i < Length; i++)
List[i] = i * 2;
}
void width_1(int *List, int Length) {
// CHECK-LABEL: @{{.*}}width_1{{.*}}(
// CHECK: br label {{.*}}, !llvm.loop ![[LOOP_16:.*]]
#pragma clang loop vectorize_width(1)
for (int i = 0; i < Length; i++)
List[i] = i * 2;
}
// CHECK: ![[LOOP_1]] = distinct !{![[LOOP_1]], ![[UNROLL_FULL:.*]]}
// CHECK: ![[UNROLL_FULL]] = !{!"llvm.loop.unroll.full"}
// CHECK: ![[LOOP_2]] = distinct !{![[LOOP_2]], ![[UNROLL_DISABLE:.*]], ![[DISTRIBUTE_DISABLE:.*]], ![[VECTORIZE_ENABLE:.*]], ![[WIDTH_8:.*]], ![[INTERLEAVE_4:.*]]}
// CHECK: ![[LOOP_2]] = distinct !{![[LOOP_2]], ![[UNROLL_DISABLE:.*]], ![[DISTRIBUTE_DISABLE:.*]], ![[WIDTH_8:.*]], ![[INTERLEAVE_4:.*]]}
// CHECK: ![[UNROLL_DISABLE]] = !{!"llvm.loop.unroll.disable"}
// CHECK: ![[DISTRIBUTE_DISABLE]] = !{!"llvm.loop.distribute.enable", i1 false}
// CHECK: ![[VECTORIZE_ENABLE]] = !{!"llvm.loop.vectorize.enable", i1 true}
// CHECK: ![[WIDTH_8]] = !{!"llvm.loop.vectorize.width", i32 8}
// CHECK: ![[INTERLEAVE_4]] = !{!"llvm.loop.interleave.count", i32 4}
// CHECK: ![[LOOP_3]] = distinct !{![[LOOP_3]], ![[INTERLEAVE_4:.*]], ![[VECTORIZE_ENABLE]], ![[FOLLOWUP_VECTOR_3:.*]]}
// CHECK: ![[LOOP_3]] = distinct !{![[LOOP_3]], ![[INTERLEAVE_4:.*]], ![[INTENABLE_1:.*]], ![[FOLLOWUP_VECTOR_3:.*]]}
// CHECK: ![[INTENABLE_1]] = !{!"llvm.loop.vectorize.enable", i1 true}
// CHECK: ![[FOLLOWUP_VECTOR_3]] = !{!"llvm.loop.vectorize.followup_all", ![[AFTER_VECTOR_3:.*]]}
// CHECK: ![[AFTER_VECTOR_3]] = distinct !{![[AFTER_VECTOR_3]], ![[ISVECTORIZED:.*]], ![[UNROLL_8:.*]]}
// CHECK: ![[ISVECTORIZED]] = !{!"llvm.loop.isvectorized"}
// CHECK: ![[UNROLL_8]] = !{!"llvm.loop.unroll.count", i32 8}
// CHECK: ![[LOOP_4]] = distinct !{![[LOOP_4]], ![[VECTORIZE_ENABLE]], ![[WIDTH_2:.*]], ![[INTERLEAVE_2:.*]]}
// CHECK: ![[LOOP_4]] = distinct !{![[LOOP_4]], ![[WIDTH_2:.*]], ![[INTERLEAVE_2:.*]]}
// CHECK: ![[WIDTH_2]] = !{!"llvm.loop.vectorize.width", i32 2}
// CHECK: ![[INTERLEAVE_2]] = !{!"llvm.loop.interleave.count", i32 2}
@ -203,7 +185,7 @@ void width_1(int *List, int Length) {
// CHECK: ![[FOLLOWUP_VECTOR_6]] = !{!"llvm.loop.vectorize.followup_all", ![[AFTER_VECTOR_6:.*]]}
// CHECK: ![[AFTER_VECTOR_6]] = distinct !{![[AFTER_VECTOR_6]], ![[ISVECTORIZED:.*]], ![[UNROLL_8:.*]]}
// CHECK: ![[LOOP_7]] = distinct !{![[LOOP_7]], ![[VECTORIZE_ENABLE]], ![[WIDTH_5:.*]]}
// CHECK: ![[LOOP_7]] = distinct !{![[LOOP_7]], ![[WIDTH_5:.*]]}
// CHECK: ![[WIDTH_5]] = !{!"llvm.loop.vectorize.width", i32 5}
// CHECK: ![[LOOP_8]] = distinct !{![[LOOP_8]], ![[WIDTH_5:.*]]}
@ -231,9 +213,5 @@ void width_1(int *List, int Length) {
// CHECK: ![[AFTER_VECTOR_13]] = distinct !{![[AFTER_VECTOR_13]], ![[ISVECTORIZED:.*]], ![[UNROLL_32:.*]]}
// CHECK: ![[UNROLL_32]] = !{!"llvm.loop.unroll.count", i32 32}
// CHECK: ![[LOOP_14]] = distinct !{![[LOOP_14]], ![[VECTORIZE_ENABLE]], ![[WIDTH_10:.*]]}
// CHECK: ![[LOOP_14]] = distinct !{![[LOOP_14]], ![[WIDTH_10:.*]]}
// CHECK: ![[WIDTH_10]] = !{!"llvm.loop.vectorize.width", i32 10}
// CHECK: ![[LOOP_15]] = distinct !{![[LOOP_15]], ![[WIDTH_1]], ![[VECTORIZE_ENABLE]]}
// CHECK-NEXT: ![[LOOP_16]] = distinct !{![[LOOP_16]], ![[VECTORIZE_ENABLE]], ![[WIDTH_1]]}