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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/43644] __uint128_t missed optimizations.
Date: Sun, 31 Dec 2023 21:39:41 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D43644

--- Comment #5 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Roger Sayle <sayle@gcc.gnu.org>:

https://gcc.gnu.org/g:79e1b23b91477b29deccf2cae92a7e8dd816c54a

commit r14-6874-g79e1b23b91477b29deccf2cae92a7e8dd816c54a
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Sun Dec 31 21:37:24 2023 +0000

    i386: Tweak define_insn_and_split to fix FAIL of
gcc.target/i386/pr43644-2.c

    This patch resolves the failure of pr43644-2.c in the testsuite, a code
    quality test I added back in July, that started failing as the code GCC
    generates for 128-bit values (and their parameter passing) has been in
    flux.

    The function:

    unsigned __int128 foo(unsigned __int128 x, unsigned long long y) {
      return x+y;
    }

    currently generates:

    foo:    movq    %rdx, %rcx
            movq    %rdi, %rax
            movq    %rsi, %rdx
            addq    %rcx, %rax
            adcq    $0, %rdx
            ret

    and with this patch, we now generate:

    foo:    movq    %rdi, %rax
            addq    %rdx, %rax
            movq    %rsi, %rdx
            adcq    $0, %rdx

    which is optimal.

    2023-12-31  Uros Bizjak  <ubizjak@gmail.com>
                Roger Sayle  <roger@nextmovesoftware.com>

    gcc/ChangeLog
            PR target/43644
            * config/i386/i386.md (*add<dwi>3_doubleword_concat_zext): Tweak
            order of instructions after split, to minimize number of moves.

    gcc/testsuite/ChangeLog
            PR target/43644
            * gcc.target/i386/pr43644-2.c: Expect 2 movq instructions.=