[Bug target/58684] New: powerpc uses only unordered floating-point compares

[Bug target/58684] New: powerpc uses only unordered floating-point compares

[jsm28 at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58684

            Bug ID: 58684
           Summary: powerpc uses only unordered floating-point compares
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jsm28 at gcc dot gnu.org
            Target: powerpc*-*

When compiling for powerpc (classic hard-float), floating-point compares always
use the fcmpu instructions that don't raise exceptions for unordered operands,
never the exception-raising fcmpo variants.  The correct behavior is to raise
exceptions for comparisons such as "x < y", but not for "x == y" or
"__builtin_isless (x, y)".

[Bug target/58684] powerpc uses only unordered floating-point compares

[dje at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58684

David Edelsohn <dje at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-03-21
                 CC|                            |bergner at gcc dot gnu.org,
                   |                            |dje at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from David Edelsohn <dje at gcc dot gnu.org> ---
This is language-dependent.  And the comparison insn must know which condition
codes will be tested.

[Bug target/58684] powerpc uses only unordered floating-point compares

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58684

--- Comment #11 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Alexandre Oliva <aoliva@gcc.gnu.org>:

https://gcc.gnu.org/g:6e95dca31c6b4688e0f0a25c9c3aa8a0bedc9056

commit r15-20-g6e95dca31c6b4688e0f0a25c9c3aa8a0bedc9056
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Sun Apr 28 04:30:24 2024 -0300

    xfail fetestexcept test - ppc always uses fcmpu

    gcc.dg/torture/pr91323.c tests that a compare with NaNf doesn't set an
    exception using builtin compare intrinsics, and that it does when
    using regular compare operators.

    That doesn't seem to be expected to work on powerpc targets.  It fails
    on GNU/Linux, it's marked to be skipped on AIX, and a similar test,
    gcc.dg/torture/pr93133.c, has the execution test xfailed for all of
    powerpc*-*-*.

    In this test, the functions that use intrinsics for the compare end up
    with the same code as the one that uses compare operators, using
    fcmpu, a floating compare that, unlike fcmpo, does not set the invalid
    operand exception for quiet NaN.  I couldn't find any evidence that
    the rs6000 backend ever outputs fcmpo.  Therefore, I'm adding the same
    execution xfail marker to this test.


    for  gcc/testsuite/ChangeLog

            PR target/58684
            * gcc.dg/torture/pr91323.c: Expect execution fail on
            powerpc*-*-*.