[Bug rtl-optimization/59036] New: [4.9 regression] Performance degradation after r204212 on 32-bit x86 targets.

[Bug rtl-optimization/59036] New: [4.9 regression] Performance degradation after r204212 on 32-bit x86 targets.

[ysrumyan at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59036

            Bug ID: 59036
           Summary: [4.9 regression] Performance degradation after r204212
                    on 32-bit x86 targets.
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ysrumyan at gmail dot com

After patch to improve register preferencing in IRA and to *remove regmove*
pass we noticed performance degradation on several benchmarks from eembc2.0
suite in 32-bit mode for all x86 targets (such as atom, slm, hsw, etc.).
This can be reproduced with attached test-case - after fix 3 more instructions
are generated for innermost loop (compiled with -O2 -m32 -march=core-avx2
options):

  before fix
.L4:
    movl    12(%esp), %edx
    addl    $3, %ecx
    movl    4(%esp), %ebx
    movl    (%esp), %ebp
    movl    8(%esp), %esi
    movzbl    (%edx,%eax), %edi
    movl    16(%esp), %edx
    movzbl    (%ebx,%eax), %ebx
    movzbl    (%esi,%eax), %esi
    addl    $1, %eax
    addl    (%edx,%edi,4), %ebp
    movzbl    0(%ebp,%ebx), %edx
    movl    28(%esp), %ebp
    movb    %dl, -3(%ecx)
    movl    24(%esp), %edx
    movl    (%edx,%edi,4), %edx
    movl    (%esp), %edi
    addl    0(%ebp,%esi,4), %edx
    leal    (%edi,%ebx), %ebp
    sarl    $16, %edx
    movzbl    0(%ebp,%edx), %edx
    movl    20(%esp), %ebp
    movb    %dl, -2(%ecx)
    movl    0(%ebp,%esi,4), %edx
    addl    %edi, %edx
    movzbl    (%edx,%ebx), %edx
    movb    %dl, -1(%ecx)
    cmpl    80(%esp), %eax
    jne    .L4

  after fix
.L4:
    movl    8(%esp), %ebx
    addl    $3, %edx
    movl    12(%esp), %esi
    movl    4(%esp), %ecx
    movzbl    (%ebx,%eax), %ebx
    movzbl    (%esi,%eax), %esi
    movzbl    (%ecx,%eax), %ecx
    addl    $1, %eax
    movb    %bl, (%esp)
    movl    16(%esp), %ebx
    movl    (%ebx,%esi,4), %ebp
    addl    %edi, %ebp
    movzbl    0(%ebp,%ecx), %ebx
    movzbl    (%esp), %ebp
    movb    %bl, -3(%edx)
    movl    24(%esp), %ebx
    movl    %ebp, (%esp)
    movl    (%ebx,%esi,4), %esi
    movl    28(%esp), %ebx
    addl    (%ebx,%ebp,4), %esi
    leal    (%edi,%ecx), %ebp
    sarl    $16, %esi
    movzbl    0(%ebp,%esi), %ebx
    movl    20(%esp), %esi
    movl    (%esp), %ebp
    movb    %bl, -2(%edx)
    movl    %edi, %ebx
    addl    (%esi,%ebp,4), %ebx
    movzbl    (%ebx,%ecx), %ecx
    movb    %cl, -1(%edx)
    cmpl    80(%esp), %eax
    jne    .L4

[Bug rtl-optimization/59036] [4.9 regression] Performance degradation after r204212 on 32-bit x86 targets.

[ysrumyan at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59036

--- Comment #1 from Yuri Rumyantsev <ysrumyan at gmail dot com> ---
Created attachment 31178
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31178&action=edit
test-case to reproduce

test need to be compiled with -m32 option for any x86 targets.

[Bug rtl-optimization/59036] [4.9 regression] Performance degradation after r204212 on 32-bit x86 targets.

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59036

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |i?86-*-*
                 CC|                            |vmakarov at gcc dot gnu.org
   Target Milestone|---                         |4.9.0

[Bug rtl-optimization/59036] [4.9 regression] Performance degradation after r204212 on 32-bit x86 targets.

[vmakarov at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59036

--- Comment #2 from Vladimir Makarov <vmakarov at gcc dot gnu.org> ---
(In reply to Yuri Rumyantsev from comment #0)
> After patch to improve register preferencing in IRA and to *remove regmove*
> pass we noticed performance degradation on several benchmarks from eembc2.0
> suite in 32-bit mode for all x86 targets (such as atom, slm, hsw, etc.).
> This can be reproduced with attached test-case - after fix 3 more
> instructions are generated for innermost loop (compiled with -O2 -m32
> -march=core-avx2 options):
> 

I am just curious what is the overall score change?  Are there only performance
degradations?  Was something improved?

In general would you prefer to reverse this patch?  Because I am affraid, it
will be only solution for the PR.

I am asking this because very frequently heuristic based optimizations generate
something better and something worse.  That is their nature.

When I worked on this optimization I had to change about 15 tests from GCC
testsuites checking AVX and found that in every tests uneccessary register
shuffling moves were deleted after applying the patch.

[Bug rtl-optimization/59036] [4.9 regression] Performance degradation after r204212 on 32-bit x86 targets.

[vmakarov at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59036

--- Comment #3 from Vladimir Makarov <vmakarov at gcc dot gnu.org> ---
Author: vmakarov
Date: Wed Nov 13 18:00:43 2013
New Revision: 204752

URL: http://gcc.gnu.org/viewcvs?rev=204752&root=gcc&view=rev
Log:
2013-11-13  Vladimir Makarov  <vmakarov@redhat.com>

    PR rtl-optimization/59036
    * ira-color.c (struct allocno_color_data): Add new members
    first_thread_allocno, next_thread_allocno, thread_freq.
    (sorted_copies): New static var.
    (allocnos_conflict_by_live_ranges_p, copy_freq_compare_func): Move
    up.
    (allocno_thread_conflict_p, merge_threads)
    (form_threads_from_copies, form_threads_from_bucket)
    (form_threads_from_colorable_allocno, init_allocno_threads): New
    functions.
    (bucket_allocno_compare_func): Add comparison by thread frequency
    and threads.
    (add_allocno_to_ordered_bucket): Rename to
    add_allocno_to_ordered_colorable_bucket.  Remove parameter.
        (push_only_colorable): Call form_threads_from_bucket.
    (color_pass): Call init_allocno_threads.  Use
    consideration_allocno_bitmap instead of coloring_allocno_bitmap
    for nuillify allocno color data.
    (ira_initiate_assign, ira_finish_assign): Allocate/free
    sorted_copies.
    (coalesce_allocnos): Use static sorted copies.


Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/ira-color.c

[Bug rtl-optimization/59036] [4.9 regression] Performance degradation after r204212 on 32-bit x86 targets.

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59036

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |FIXED

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
I suppose fixed.