[Bug target/66369] gcc 4.8.3/5.1.0 miss optimisation with vpmovmskb

["ubizjak at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66369

--- Comment #2 from Uroš Bizjak <ubizjak at gmail dot com> ---
I have looked briefly at this. The compiler actually generates the following:

        vpmovmskb       %ymm0, %edx     # 16    avx2_pmovmskb   [length = 4]
        testl   %edx, %edx      # 18    *cmpsi_ccno_1/1 [length = 2]
        je      .L5     # 19    *jcc_1  [length = 2]
        movslq  %edx, %rdx      # 21    *extendsidi2_rex64/2    [length = 3]
        tzcntq  %rdx, %rdx      # 52    *ctzdi2_falsedep        [length = 5]

from:

  int _14;
  long unsigned int v.1_15;
  int _16;
  ...
  _14 = __builtin_ia32_pmovmskb256 (_13);
  if (_14 != 0)
    goto <bb 5>;
  else
    goto <bb 6>;

  <bb 5>:
  v.1_15 = (long unsigned int) _14;
  _16 = __builtin_ctzl (v.1_15);
  _17 = (long int) _16;

The intrinsic returns "int", and from the above tree dump, the compiler won't
even consider to combine the sign-extension with vpmovmskb.

So, why not:

   unsigned int v;

   v = (unsigned int) _mm256_movemask_epi8( ... );
   if (v != 0)
      return (long) __builtin_ctz( v );
>From gcc-bugs-return-487815-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Tue Jun 02 10:21:32 2015
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From: "fxcoudert at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/66377] New: [F95] Wrong-code with equivalenced array in module
Date: Tue, 02 Jun 2015 10:21:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idf377

            Bug ID: 66377
           Summary: [F95] Wrong-code with equivalenced array in module
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fxcoudert at gcc dot gnu.org
  Target Milestone: ---

This code:

module constant
  integer :: x(2), x1, x2
  equivalence (x(1),x1), (x(2),x2)
end module

program test
  use constant
  x = (/1, 2/)
  call another()
contains
  subroutine another()
    use constant, only : x1
    print *, x1
  end subroutine
end program

should output "1", but outputs "0" with all versions of gfortran tested.