[Bug middle-end/100942] New: ccmp is not used if the value is used later

[Bug middle-end/100942] New: ccmp is not used if the value is used later

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100942

            Bug ID: 100942
           Summary: ccmp is not used if the value is used later
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---
            Target: aarch64-linux-gnu

Take:
void foo(void);
int f1(int a, int b)
{
  int c = a == 0 || b == 0;
  if (c) foo();
  return c;
}
------ CUT -----
Right now we produce at -O2:
        stp     x29, x30, [sp, -32]!
        cmp     w0, 0
        mov     x29, sp
        str     x19, [sp, 16]
        cset    w19, eq
        cmp     w1, 0
        cset    w0, eq
        orr     w19, w19, w0
        cbnz    w19, .L8
        mov     w0, w19
        ldr     x19, [sp, 16]
        ldp     x29, x30, [sp], 32
        ret

Notice how we have cmp/cset/cmp/cset/orr.
This is a (much) reduced testcase from Xalan in SPEC 2k6.

[Bug middle-end/100942] ccmp is not used if the value is used later

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100942

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |pinskia at gcc dot gnu.org
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-12-12

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I have a fix.

[Bug middle-end/100942] ccmp is not used if the value is used later

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100942

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Created attachment 56860
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=56860&action=edit
Patch which I am testing

Patch which I am testing. Will be doing some benchmarking too.

[Bug middle-end/100942] ccmp is not used if the value is used later

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100942

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                URL|                            |https://gcc.gnu.org/piperma
                   |                            |il/gcc-patches/2023-Decembe
                   |                            |r/640289.html
           Keywords|                            |patch

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Patch posted:
https://gcc.gnu.org/pipermail/gcc-patches/2023-December/640289.html

[Bug middle-end/100942] ccmp is not used if the value is used later

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100942

--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Richard Sandiford <rsandifo@gcc.gnu.org>:

https://gcc.gnu.org/g:06ee648e9bb8c121fbd93659f81d3380dba8be09

commit r14-8372-g06ee648e9bb8c121fbd93659f81d3380dba8be09
Author: Andrew Pinski <quic_apinski@quicinc.com>
Date:   Tue Jan 23 17:42:51 2024 +0000

    aarch64/expr: Use ccmp when the outer expression is used twice [PR100942]

    Ccmp is not used if the result of the and/ior is used by both
    a GIMPLE_COND and a GIMPLE_ASSIGN. This improves the code generation
    here by using ccmp in this case.
    Two changes is required, first we need to allow the outer statement's
    result be used more than once.
    The second change is that during the expansion of the gimple, we need
    to try using ccmp. This is needed because we don't use expand the ssa
    name of the lhs but rather expand directly from the gimple.

    A small note on the ccmp_4.c testcase, we should be able to get slightly
    better than with this patch but it is one extra instruction compared to
    before.

            PR target/100942

    gcc/ChangeLog:

            * ccmp.cc (ccmp_candidate_p): Add outer argument.
            Allow if the outer is true and the lhs is used more
            than once.
            (expand_ccmp_expr): Update call to ccmp_candidate_p.
            * expr.h (expand_expr_real_gassign): Declare.
            * expr.cc (expand_expr_real_gassign): New function, split out
from...
            (expand_expr_real_1): ...here.
            * cfgexpand.cc (expand_gimple_stmt_1): Use
expand_expr_real_gassign.

    gcc/testsuite/ChangeLog:

            * gcc.target/aarch64/ccmp_3.c: New test.
            * gcc.target/aarch64/ccmp_4.c: New test.
            * gcc.target/aarch64/ccmp_5.c: New test.

    Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>
    Co-Authored-By: Richard Sandiford <richard.sandiford@arm.com>

[Bug middle-end/100942] ccmp is not used if the value is used later

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100942

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
   Target Milestone|---                         |14.0
             Status|ASSIGNED                    |RESOLVED

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Fixed. Thanks Richard S. for taking the patch the rest of the way.