[Bug target/110796] builtin_iseqsig fails some tests in armv8l-linux-gnueabihf

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110796

--- Comment #16 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-15 branch has been updated by Richard Earnshaw
<rearnsha@gcc.gnu.org>:

https://gcc.gnu.org/g:746e09b32b5dde185aef06a405b5c643e5a595e7

commit r15-10565-g746e09b32b5dde185aef06a405b5c643e5a595e7
Author: Richard Earnshaw <rearnsha@arm.com>
Date:   Fri Mar 28 12:59:03 2025 +0000

    arm: Only reverse FP inequalities when -ffinite-math-only [PR110796...]

    On Arm we have been failing to fully implement support for IEEE NaNs
    in inequality comparisons because we have allowed reversing of
    inequalities in a way that allows SELECT_CC_MODE to produce different
    answers.  For example, the reverse of GT is UNLE, but if we pass these
    two RTL codes to SELECT_CC_MODE, the former will return CCFPEmode,
    while the latter CCFPmode.

    It would be possible to allow fully reversible FPmodes, but to do so
    would involve adding yet more RTL codes, something like NOT_GT and
    NOT_UNLE, for the cases we cannot currently reverse.  NOT_GT would
    then have the same condition code generation as UNLT, but the same
    mode selection as GT.

    In the mean time, we need to restrict REVERSIBLE_CC_MODE to
    non-floating modes unless we are compiling with -ffinite-math-only.  In
    that case we can continue to reverse the comparisons, but now we want
    to always select CCFPmode as there's no need to consider the exception
    raising cases.

            PR target/110796
            PR target/118446

    gcc/ChangeLog:

            * config/arm/arm.h (REVERSIBLE_CC_MODE): FP modes are only
            reversible if flag_finite_math_only.
            * config/arm/arm.cc (arm_select_cc_mode): Return CCFPmode for all
            FP comparisons if flag_finite_math_only.

    gcc/testsuite/ChangeLog:

            * gcc.target/arm/armv8_2-fp16-arith-1.c: Adjust due to no-longer
            emitting VCMPE when -ffast-math..

    (cherry picked from commit 0a339746e7646bacf2c8aa5512268d23660f26f9)