[Bug tree-optimization/78200] [7 regression]: 429.mcf of cpu2006 regresses in GCC trunk for avx2 target.

["venkataramanan.kumar at amd dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78200

--- Comment #1 from Venkataramanan <venkataramanan.kumar at amd dot com> ---
(In reply to Venkataramanan from comment #0)
> Noticed 5% regression with 429.mcf of cpu2006 on x86_64 AVX2 (bdver4) with
> GCC trunk gcc version 7.0.0 20161028 (experimental) (GCC).
> 
> Flag used is -O3 -mavx2 -mprefer-avx128
> 
> Not seen with GCC 6.1 or with GCC trunk for -O3 -mavx -mprefer-avx128
> 
> Assembly difference is observed in hot function primal_bea_mpp of pbeampp.c. 
> 
> -O3 -mavx -mprefer-avx128		-O3 -mavx2 -mprefer-avx128
> 
> .L98:                                 |  .L98:
>   ------------------------------------|          jle     .L97 <==  order of
> comparison 
>           cmpl    $2, %r9d            |          cmpl    $2, %r9d  is
> different.
>           jne     .L97                |          jne     .L97
>           testq   %rdi, %rdi          |  -----------------------------------
>           jle     .L97                |  -----------------------------------
>   .L99:                               |  .L99:
>           addq    $1, %r13            |          addq    $1, %r13
>           movq    %rdi, %r12          |          movq    %rdi, %r12
>           movq    perm(,%r13,8), %r9  |          movq    perm(,%r13,8), %r9
>           sarq    $63, %r12           |          sarq    $63, %r12
>           movq    %rdi, 8(%r9)        |          movq    %rdi, 8(%r9)
> + +-- 12 lines: xorq %r12, %rdi-------|+ +-- 12 lines: xorq %r12, %rdi------
>           jle     .L97                |          jle     .L97
>           movq    8(%rax), %r14       |          movq    8(%rax), %r14
>           movq    (%rax), %rdi        |          movq    (%rax), %rdi
>           subq    (%r14), %rdi        |          subq    (%r14), %rdi
>           movq    16(%rax), %r14      |          movq    16(%rax), %r14
>           addq    (%r14), %rdi        |          addq    (%r14), %rdi
>           jns     .L98                |          cmpq    $0, %rdi
>   ------------------------------------|          jge     .L98
> 
> 
> Gimple optimzied dump shows 
> 
> GCC trunk -O3 -mavx -mprefer-avx128 
> ;;   basic block 20, loop depth 2, count 0, freq 1067, maybe hot
> ;;   Invalid sum of incoming frequencies 1216, should be 1067
> ;;    prev block 19, next block 21, flags: (NEW, REACHABLE, VISITED)
> ;;    pred:       18 [64.0%]  (FALSE_VALUE,EXECUTABLE)
>   # RANGE [0, 1]
>   _496 = _512 == 2;
>   # RANGE [0, 1]
>   _495 = red_cost_503 > 0;
>   # RANGE [0, 1]
>   _494 = _495 & _496;
>   if (_494 != 0)
>     goto <bb 21>;
>   else
>     goto <bb 22>;
> 
for GCC trunk -O3 -mavx -mprefer-avx128 optimized dumps look like this.
;;   basic block 20, loop depth 2, count 0, freq 1067, maybe hot
;;   Invalid sum of incoming frequencies 1216, should be 1067
;;    prev block 19, next block 21, flags: (NEW, REACHABLE, VISITED)
;;    pred:       18 [64.0%]  (FALSE_VALUE,EXECUTABLE)
  # RANGE [0, 1]
  _340 = _23 == 2;
  # RANGE [0, 1]
  _341 = red_cost_86 > 0;
  # RANGE [0, 1]
  _338 = _340 & _341;
  if (_338 != 0)
    goto <bb 21>;
  else
    goto <bb 22>;