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

[Jakub Jelinek <jakub@redhat.com>]

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.

--- 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