[Bug middle-end/31985] Wide operations (i.e. adddi3) are split too late

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=31985

--- Comment #4 from CVS 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:95020d33ad6991fe4fbdccf70e7133116cac68f4

commit r14-1892-g95020d33ad6991fe4fbdccf70e7133116cac68f4
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Fri Jun 16 16:18:27 2023 +0100

    PR target/31985: Improve memory operand use with doubleword add.

    This patch addresses the last remaining issue with PR target/31985, that
    GCC could make better use of memory addressing modes when implementing
    double word addition.  This is achieved by adding a define_insn_and_split
    that combines an *add<dwi>3_doubleword with a *concat<mode><dwi>3, so
    that the components of the concat can be used directly, without first
    being loaded into a double word register.

    For test_c in the bugzilla PR:

    Before:
            pushl   %ebx
            subl    $16, %esp
            movl    28(%esp), %eax
            movl    36(%esp), %ecx
            movl    32(%esp), %ebx
            movl    24(%esp), %edx
            addl    %ecx, %eax
            adcl    %ebx, %edx
            movl    %eax, 8(%esp)
            movl    %edx, 12(%esp)
            addl    $16, %esp
            popl    %ebx
            ret

    After:
    test_c:
            subl    $20, %esp
            movl    36(%esp), %eax
            movl    32(%esp), %edx
            addl    28(%esp), %eax
            adcl    24(%esp), %edx
            movl    %eax, 8(%esp)
            movl    %edx, 12(%esp)
            addl    $20, %esp
            ret

    2023-06-16  Roger Sayle  <roger@nextmovesoftware.com>
                Uros Bizjak  <ubizjak@gmail.com>

    gcc/ChangeLog
            PR target/31985
            * config/i386/i386.md (*add<dwi>3_doubleword_concat): New
            define_insn_and_split combine *add<dwi>3_doubleword with
            a *concat<mode><dwi>3 for more efficient lowering after reload.

    gcc/testsuite/ChangeLog
            PR target/31985
            * gcc.target/i386/pr31985.c: New test case.