wxiao3 added inline comments.
================
Comment at: clang/lib/CodeGen/CodeGenFunction.cpp:496
// function.
- CurFn->addFnAttr("min-legal-vector-width", llvm::utostr(LargestVectorWidth));
+ if (LargestVectorWidth)
+ CurFn->addFnAttr("min-legal-vector-width",
llvm::utostr(LargestVectorWidth));
----------------
lebedev.ri wrote:
> wxiao3 wrote:
> > For x86 backend, "LargestVectorWidth" default value is not zero but
> > UINT32_MAX.
> > Please refer to:
> > https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/X86/X86TargetMachine.cpp#L271
> > Suggest revert this patch since it changes the code generated for x86.
> Reproducer please?
```
$ cat test.c
void foo(float* in, float* __restrict out, int n)
{
int i;
for (i = 0; i < n; i++) {
out[i] = i + 2*in[i];
}
}
```
Before this patch
```
$ clang -Ofast -march=skylake-avx512 -mllvm -force-vector-width=16
-mprefer-vector-width=256 -S -o - test.c | grep ymm | wc
57 333 2687
```
After this patch
```
$ clang -Ofast -march=skylake-avx512 -mllvm -force-vector-width=16
-mprefer-vector-width=256 -S -o - test.c | grep ymm | wc
0 0 0
```
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D97116/new/
https://reviews.llvm.org/D97116
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