On Sun, Mar 13, 2022 at 3:28 AM Jakub Jelinek <ja...@redhat.com> wrote:
>
> Hi!
>
> These intrinsics are supposed to do an unaligned may_alias load
> of a 16-bit or 32-bit value and store it as the first element of
> a 128-bit integer vector, with all other elements cleared.
>
> The current _mm_storeu_* implementation implements that correctly, uses
> __*_u types to do the store and extracts the first element of a vector into
> it.
> But _mm_loadu_si{16,32} gets it all wrong. It performs an aligned
> non-may_alias load and because _mm_set_epi{16,32} has the args reversed,
> it also inserts it into the last vector element instead of first.
>
> The following patch fixes that, bootstrapped/regtested on x86_64-linux
> and i686-linux, ok for trunk and affected release branches?
LGTM, thanks for handling this.
>
> Note, while the Intrinsics guide for _mm_loadu_si32 says SSE2,
> for _mm_loadu_si16 it says strangely SSE. But the intrinsics
> returns __m128i, which is only defined in emmintrin.h, and
> _mm_set_epi16 is also only SSE2 and later in emmintrin.h.
> Even clang defines it in emmintrin.h and ends up with inlining
> failure when calling _mm_loadu_si16 from sse,no-sse2 function.
> So, isn't that a bug in the intrinsic guide instead?
I think it's a bug, it's supposed to generate movzx + movd, and movd
is under sse2, and have reported it to the colleague who maintains
Intel intrinsic guide.
Similar bug for
_mm_loadu_si64
_mm_storeu_si16
_mm_storeu_si64
>
> 2022-03-12 Jakub Jelinek <ja...@redhat.com>
>
> PR target/99754
> * config/i386/emmintrin.h (_mm_loadu_si32): Put loaded value into
> first rather than last element of the vector, use __m32_u to do
> a really unaligned load, use just 0 instead of (int)0.
> (_mm_loadu_si16): Put loaded value into first rather than last
> element of the vector, use __m16_u to do a really unaligned load,
> use just 0 instead of (short)0.
>
> * gcc.target/i386/pr99754-1.c: New test.
> * gcc.target/i386/pr99754-2.c: New test.
>
> --- gcc/config/i386/emmintrin.h.jj 2022-01-11 23:11:21.766298923 +0100
> +++ gcc/config/i386/emmintrin.h 2022-03-11 16:47:24.789884825 +0100
> @@ -718,14 +718,13 @@ _mm_loadu_si64 (void const *__P)
> extern __inline __m128i __attribute__((__gnu_inline__, __always_inline__,
> __artificial__))
> _mm_loadu_si32 (void const *__P)
> {
> - return _mm_set_epi32 (*(int *)__P, (int)0, (int)0, (int)0);
> + return _mm_set_epi32 (0, 0, 0, (*(__m32_u *)__P)[0]);
> }
>
> extern __inline __m128i __attribute__((__gnu_inline__, __always_inline__,
> __artificial__))
> _mm_loadu_si16 (void const *__P)
> {
> - return _mm_set_epi16 (*(short *)__P, (short)0, (short)0, (short)0,
> - (short)0, (short)0, (short)0, (short)0);
> + return _mm_set_epi16 (0, 0, 0, 0, 0, 0, 0, (*(__m16_u *)__P)[0]);
> }
>
> extern __inline void __attribute__((__gnu_inline__, __always_inline__,
> __artificial__))
> --- gcc/testsuite/gcc.target/i386/pr99754-1.c.jj 2022-03-11
> 16:43:30.621120896 +0100
> +++ gcc/testsuite/gcc.target/i386/pr99754-1.c 2022-03-11 16:43:18.250291856
> +0100
> @@ -0,0 +1,20 @@
> +/* PR target/99754 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -msse2" } */
> +/* { dg-require-effective-target sse2 } */
> +
> +#include "sse2-check.h"
> +#include <emmintrin.h>
> +
> +static void
> +sse2_test (void)
> +{
> + union { unsigned char buf[32]; long long ll; } u;
> + u.buf[1] = 0xfe;
> + u.buf[2] = 0xca;
> + u.buf[17] = 0xaa;
> + u.buf[18] = 0x55;
> + _mm_storeu_si16 (&u.buf[17], _mm_loadu_si16 (&u.buf[1]));
> + if (u.buf[17] != 0xfe || u.buf[18] != 0xca)
> + abort ();
> +}
> --- gcc/testsuite/gcc.target/i386/pr99754-2.c.jj 2022-03-11
> 16:43:41.701967763 +0100
> +++ gcc/testsuite/gcc.target/i386/pr99754-2.c 2022-03-11 16:45:16.391659211
> +0100
> @@ -0,0 +1,24 @@
> +/* PR target/99754 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -msse2" } */
> +/* { dg-require-effective-target sse2 } */
> +
> +#include "sse2-check.h"
> +#include <emmintrin.h>
> +
> +static void
> +sse2_test (void)
> +{
> + union { unsigned char buf[32]; long long ll; } u;
> + u.buf[1] = 0xbe;
> + u.buf[2] = 0xba;
> + u.buf[3] = 0xfe;
> + u.buf[4] = 0xca;
> + u.buf[17] = 0xaa;
> + u.buf[18] = 0x55;
> + u.buf[19] = 0xaa;
> + u.buf[20] = 0x55;
> + _mm_storeu_si32 (&u.buf[17], _mm_loadu_si32 (&u.buf[1]));
> + if (u.buf[17] != 0xbe || u.buf[18] != 0xba || u.buf[19] != 0xfe ||
> u.buf[20] != 0xca)
> + abort ();
> +}
>
> Jakub
>
--
BR,
Hongtao
