i386: Fix up -Wuninitialized warnings in avx512erintrin.h [PR105593]

  Hi!

As reported in the PR, there are some -Wuninitialized warnings in
avx512erintrin.h.  One can see that by compiling sse-23.c testcase with
-Wuninitialized (or when actually using those intrinsics).
Those 6 spots use an uninitialized variable and pass it as one of the
argument to a builtin with constant mask -1, because there is no unmasked
builtin.  It is true that expansion of those builtins into RTL will see
mask is all ones and ignore the unneeded argument, but -Wuninitialized
is diagnosed on GIMPLE and on GIMPLE these builtins are just builtin calls.
avx512fintrin.h and other headers use in these cases the _mm*_undefined_* ()
intrinsics, like:
  return (__m512i) __builtin_ia32_psrav8di_mask ((__v8di) __X,
                                                 (__v8di) __Y,
                                                 (__v8di)
                                                 _mm512_undefined_epi32 (),
                                                 (__mmask8) -1);
etc. and the following patch does the same for avx512erintrin.h.
With the recent changes in C++ FE and the _mm*_undefined_* intrinsics,
we don't emit -Wuninitialized warnings for those (previously we didn't
just in C due to self-initialization).  Of course we could also
just self-initialize these uninitialized vars and add the #pragma GCC
diagnostic dances around it, but using the intrinsics is consistent with
the rest and IMHO cleaner.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2023-01-31  Jakub Jelinek  <jakub@redhat.com>

	PR c++/105593
	* config/i386/avx512erintrin.h (_mm512_exp2a23_round_pd,
	_mm512_exp2a23_round_ps, _mm512_rcp28_round_pd, _mm512_rcp28_round_ps,
	_mm512_rsqrt28_round_pd, _mm512_rsqrt28_round_ps): Use
	_mm512_undefined_pd () or _mm512_undefined_ps () instead of using
	uninitialized automatic variable __W.

	* gcc.target/i386/sse-23.c: Add -Wuninitialized to dg-options.


	Jakub
  

> -----Original Message-----
> From: Jakub Jelinek <jakub@redhat.com>
> Sent: Tuesday, January 31, 2023 4:09 PM
> To: Liu, Hongtao <hongtao.liu@intel.com>; Uros Bizjak <ubizjak@gmail.com>
> Cc: gcc-patches@gcc.gnu.org
> Subject: [PATCH] i386: Fix up -Wuninitialized warnings in avx512erintrin.h
> [PR105593]
> 
> Hi!
> 
> As reported in the PR, there are some -Wuninitialized warnings in
> avx512erintrin.h.  One can see that by compiling sse-23.c testcase with -
> Wuninitialized (or when actually using those intrinsics).
> Those 6 spots use an uninitialized variable and pass it as one of the argument
> to a builtin with constant mask -1, because there is no unmasked builtin.  It is
> true that expansion of those builtins into RTL will see mask is all ones and
> ignore the unneeded argument, but -Wuninitialized is diagnosed on GIMPLE
> and on GIMPLE these builtins are just builtin calls.
> avx512fintrin.h and other headers use in these cases the _mm*_undefined_*
> () intrinsics, like:
>   return (__m512i) __builtin_ia32_psrav8di_mask ((__v8di) __X,
>                                                  (__v8di) __Y,
>                                                  (__v8di)
>                                                  _mm512_undefined_epi32 (),
>                                                  (__mmask8) -1); etc. and the following patch does
> the same for avx512erintrin.h.
> With the recent changes in C++ FE and the _mm*_undefined_* intrinsics, we
> don't emit -Wuninitialized warnings for those (previously we didn't just in C
> due to self-initialization).  Of course we could also just self-initialize these
> uninitialized vars and add the #pragma GCC diagnostic dances around it, but
> using the intrinsics is consistent with the rest and IMHO cleaner.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Ok, thanks.
> 
> 2023-01-31  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR c++/105593
> 	* config/i386/avx512erintrin.h (_mm512_exp2a23_round_pd,
> 	_mm512_exp2a23_round_ps, _mm512_rcp28_round_pd,
> _mm512_rcp28_round_ps,
> 	_mm512_rsqrt28_round_pd, _mm512_rsqrt28_round_ps): Use
> 	_mm512_undefined_pd () or _mm512_undefined_ps () instead of
> using
> 	uninitialized automatic variable __W.
> 
> 	* gcc.target/i386/sse-23.c: Add -Wuninitialized to dg-options.
> 
> --- gcc/config/i386/avx512erintrin.h.jj	2023-01-16 11:52:15.944736113
> +0100
> +++ gcc/config/i386/avx512erintrin.h	2023-01-30 20:53:08.057769691
> +0100
> @@ -51,9 +51,8 @@ extern __inline __m512d  __attribute__
> ((__gnu_inline__, __always_inline__, __artificial__))
> _mm512_exp2a23_round_pd (__m512d __A, int __R)  {
> -  __m512d __W;
>    return (__m512d) __builtin_ia32_exp2pd_mask ((__v8df) __A,
> -					       (__v8df) __W,
> +					       (__v8df) _mm512_undefined_pd
> (),
>  					       (__mmask8) -1, __R);
>  }
> 
> @@ -79,9 +78,8 @@ extern __inline __m512  __attribute__
> ((__gnu_inline__, __always_inline__, __artificial__))
> _mm512_exp2a23_round_ps (__m512 __A, int __R)  {
> -  __m512 __W;
>    return (__m512) __builtin_ia32_exp2ps_mask ((__v16sf) __A,
> -					      (__v16sf) __W,
> +					      (__v16sf) _mm512_undefined_ps
> (),
>  					      (__mmask16) -1, __R);
>  }
> 
> @@ -107,9 +105,8 @@ extern __inline __m512d  __attribute__
> ((__gnu_inline__, __always_inline__, __artificial__))
> _mm512_rcp28_round_pd (__m512d __A, int __R)  {
> -  __m512d __W;
>    return (__m512d) __builtin_ia32_rcp28pd_mask ((__v8df) __A,
> -						(__v8df) __W,
> +						(__v8df)
> _mm512_undefined_pd (),
>  						(__mmask8) -1, __R);
>  }
> 
> @@ -135,9 +132,8 @@ extern __inline __m512  __attribute__
> ((__gnu_inline__, __always_inline__, __artificial__))
> _mm512_rcp28_round_ps (__m512 __A, int __R)  {
> -  __m512 __W;
>    return (__m512) __builtin_ia32_rcp28ps_mask ((__v16sf) __A,
> -					       (__v16sf) __W,
> +					       (__v16sf) _mm512_undefined_ps
> (),
>  					       (__mmask16) -1, __R);
>  }
> 
> @@ -229,9 +225,8 @@ extern __inline __m512d  __attribute__
> ((__gnu_inline__, __always_inline__, __artificial__))
> _mm512_rsqrt28_round_pd (__m512d __A, int __R)  {
> -  __m512d __W;
>    return (__m512d) __builtin_ia32_rsqrt28pd_mask ((__v8df) __A,
> -						  (__v8df) __W,
> +						  (__v8df)
> _mm512_undefined_pd (),
>  						  (__mmask8) -1, __R);
>  }
> 
> @@ -257,9 +252,8 @@ extern __inline __m512  __attribute__
> ((__gnu_inline__, __always_inline__, __artificial__))
> _mm512_rsqrt28_round_ps (__m512 __A, int __R)  {
> -  __m512 __W;
>    return (__m512) __builtin_ia32_rsqrt28ps_mask ((__v16sf) __A,
> -						 (__v16sf) __W,
> +						 (__v16sf)
> _mm512_undefined_ps (),
>  						 (__mmask16) -1, __R);
>  }
> 
> --- gcc/testsuite/gcc.target/i386/sse-23.c.jj	2022-11-07
> 10:30:42.831628746 +0100
> +++ gcc/testsuite/gcc.target/i386/sse-23.c	2023-01-30
> 20:48:28.858838817 +0100
> @@ -1,5 +1,5 @@
>  /* { dg-do compile } */
> -/* { dg-options "-O2 -Werror-implicit-function-declaration -march=k8" } */
> +/* { dg-options "-O2 -Werror-implicit-function-declaration
> +-Wuninitialized -march=k8" } */
>  /* { dg-add-options bind_pic_locally } */
> 
>  #include <mm_malloc.h>
> 
> 	Jakub