858a1ae37d
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
77 lines
2.3 KiB
C++
77 lines
2.3 KiB
C++
// RUN: %clang_cc1 -triple x86_64-apple-darwin -std=c++11 -emit-llvm -o - %s | FileCheck %s
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void test0(int *List, int Length) {
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// CHECK-LABEL: @{{.*}}test0{{.*}}(
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// CHECK: br label {{.*}}, !llvm.loop ![[LOOP0:.*]]
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#pragma clang loop vectorize(enable)
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for (int i = 0; i < Length; i++)
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List[i] = i * 2;
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}
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void test1(int *List, int Length) {
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// CHECK-LABEL: @{{.*}}test1{{.*}}(
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// CHECK: br label {{.*}}, !llvm.loop ![[LOOP1:.*]]
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#pragma clang loop vectorize(enable) vectorize_predicate(enable)
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for (int i = 0; i < Length; i++)
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List[i] = i * 2;
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}
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void test2(int *List, int Length) {
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// CHECK-LABEL: @{{.*}}test2{{.*}}(
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// CHECK: br label {{.*}}, !llvm.loop ![[LOOP2:.*]]
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#pragma clang loop vectorize(enable) vectorize_predicate(disable)
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for (int i = 0; i < Length; i++)
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List[i] = i * 2;
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}
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// vectorize_predicate(enable) implies vectorize(enable)
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void test3(int *List, int Length) {
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// CHECK-LABEL: @{{.*}}test3{{.*}}(
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// CHECK: br label {{.*}}, !llvm.loop ![[LOOP3:.*]]
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#pragma clang loop vectorize_predicate(enable)
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for (int i = 0; i < Length; i++)
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List[i] = i * 2;
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}
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// Check that disabling vectorization means a vectorization width of 1, and
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// also that vectorization_predicate isn't enabled.
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void test4(int *List, int Length) {
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// CHECK-LABEL: @{{.*}}test4{{.*}}(
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// CHECK: br label {{.*}}, !llvm.loop ![[LOOP4:.*]]
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#pragma clang loop vectorize(disable)
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for (int i = 0; i < Length; i++)
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List[i] = i * 2;
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}
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// Check that vectorize and vectorize_predicate are disabled.
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void test5(int *List, int Length) {
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// CHECK-LABEL: @{{.*}}test5{{.*}}(
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// CHECK: br label {{.*}}, !llvm.loop ![[LOOP5:.*]]
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#pragma clang loop vectorize(disable) vectorize_predicate(enable)
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for (int i = 0; i < Length; i++)
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List[i] = i * 2;
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}
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// CHECK: ![[LOOP0]] = distinct !{![[LOOP0]], !3}
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// CHECK-NEXT: !3 = !{!"llvm.loop.vectorize.enable", i1 true}
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// CHECK-NEXT: ![[LOOP1]] = distinct !{![[LOOP1]], !5, !3}
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// CHECK-NEXT: !5 = !{!"llvm.loop.vectorize.predicate.enable", i1 true}
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// CHECK-NEXT: ![[LOOP2]] = distinct !{![[LOOP2]], !7, !3}
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// CHECK-NEXT: !7 = !{!"llvm.loop.vectorize.predicate.enable", i1 false}
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// CHECK-NEXT: ![[LOOP3]] = distinct !{![[LOOP3]], !5, !3}
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// CHECK-NEXT: ![[LOOP4]] = distinct !{![[LOOP4]], !10}
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// CHECK-NEXT: !10 = !{!"llvm.loop.vectorize.width", i32 1}
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// CHECK-NEXT: ![[LOOP5]] = distinct !{![[LOOP5]], !10}
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