[Bug c++/105593] avx512 math function raises uninitialized variable warning

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105593

--- Comment #31 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:c3ba6680492ee1ddef6ae8493787c36c45c2d20e

commit r12-9163-gc3ba6680492ee1ddef6ae8493787c36c45c2d20e
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Tue Jan 31 09:20:34 2023 +0100

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

    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.

    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.

    (cherry picked from commit 41602390456901c14ecdfa2fa64c3cebd5b6ff09)