chenxiaolong <chenxiaol...@loongson.cn> writes:
> After the detection of maximum reduction is enabled on LoongArch architecture,
> the regression test of GCC finds that vect-fmin-3.c fails. Currently, in the
> target-supports.exp file, only aarch64,arm,riscv, and LoongArch architectures
> are supported. Through analysis, the "-ffast-math" compilation option needs to
> be added to the test case in order to successfully reduce using vectorization.
> The original patch was submitted by author Richard Sandiford.
>
> The initial patch information submitted is as follows:
>
> commit e32b9eb32d7cd2d39bf9c70497890ac61b9ee14c
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/vect/vect-fmin-3.c:Adding an extra "-ffast-math" to the
> compilation option ensures that the loop can be reduced to maximum
> success.
This shouldn't be necessary. The test does:
for (int i = 0; i < n; i += 2)
{
x0 = __builtin_fmin (x0, ptr[i + 0]);
x1 = __builtin_fmin (x1, ptr[i + 1]);
}
res[0] = x0;
res[1] = x1;
__builtin_fmin is an FP minimum operation that corresponds directly to
the fmin*3 optab (or reduc_fmin_scal_* for reductions). It is naturally
associative, so doesn't need -ffast-math for that.
Does LoongArch provide reduc_min_scal_* but not reduc_fmin_scal_*?
If so, we probably need a new target selector for fmin/fmax reduction.
Thanks,
Richard
> ---
> gcc/testsuite/gcc.dg/vect/vect-fmin-3.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/gcc/testsuite/gcc.dg/vect/vect-fmin-3.c
> b/gcc/testsuite/gcc.dg/vect/vect-fmin-3.c
> index 2e282ba6878..edef57925c1 100644
> --- a/gcc/testsuite/gcc.dg/vect/vect-fmin-3.c
> +++ b/gcc/testsuite/gcc.dg/vect/vect-fmin-3.c
> @@ -1,4 +1,5 @@
> /* { dg-require-effective-target vect_float } */
> +/* { dg-additional-options "-ffast-math" } */
>
> #include "tree-vect.h"
