Re: [PATCH][RTL-ifcvt] Improve conditional select ops on immediates

[Uros Bizjak <ubizjak@gmail.com>]

Hello!

> 2015-07-30  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>
>     * ifcvt.c (noce_try_store_flag_constants): Make logic of the case
>     when diff == STORE_FLAG_VALUE or diff == -STORE_FLAG_VALUE more
>     explicit.  Prefer to add the flag whenever possible.
>     (noce_process_if_block): Try noce_try_store_flag_constants before
>     noce_try_cmove.
>
> 2015-07-30  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>
>     * gcc.target/aarch64/csel_bfx_1.c: New test.
>     * gcc.target/aarch64/csel_imms_inc_1.c: Likewise.

This patch regressed following tests on x86_64:

FAIL: gcc.target/i386/cmov2.c scan-assembler sbb
FAIL: gcc.target/i386/cmov3.c scan-assembler cmov[^3]

While cmov3 case is questionable by itself in light of PR56309 [1],
the cnov2 case regressed from:

       cmpl    %edi, %esi
       sbbl    %eax, %eax
       andl    $-10, %eax
       addl    $5, %eax
       ret

to:

       xorl    %eax, %eax
       cmpl    %esi, %edi
       setbe   %al
       negl    %eax
       andl    $10, %eax
       subl    $5, %eax
       ret

Please note that sbb (aka {*x86_movsicc_0_m1} ) is not generated
anymore. Non-QImode setcc instructions are problematic on x86, since
they need to be zero-extended to their full length.

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56309

Uros.