[Bug target/85730] complex code for modifying lowest byte in a 4-byte vector

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85730

--- Comment #10 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Uros Bizjak <uros@gcc.gnu.org>:

https://gcc.gnu.org/g:b37351e3279d192d5d4682f002abe5b2e133bba6

commit r12-4359-gb37351e3279d192d5d4682f002abe5b2e133bba6
Author: Uros Bizjak <ubizjak@gmail.com>
Date:   Tue Oct 12 18:20:38 2021 +0200

    i386: Improve workaround for PR82524 LRA limitation [PR85730]

    As explained in PR82524, LRA is not able to reload strict_low_part inout
    operand with matched input operand. The patch introduces a workaround,
    where we allow LRA to generate an instruction with non-matched input
operand
    which is split post reload to an instruction that inserts non-matched input
    operand to an inout operand and the instruction that uses matched operand.

    The generated code improves from:

            movsbl  %dil, %edx
            movl    %edi, %eax
            sall    $3, %edx
            movb    %dl, %al

    to:

            movl    %edi, %eax
            movb    %dil, %al
            salb    $3, %al

    which is still not optimal, but the code is one instruction shorter and
    does not use a temporary register.

    2021-10-12  Uroš Bizjak  <ubizjak@gmail.com>

    gcc/
            PR target/85730
            PR target/82524
            * config/i386/i386.md (*add<mode>_1_slp): Rewrite as
            define_insn_and_split pattern.  Add alternative 1 and split it
            post reload to insert operand 1 into the low part of operand 0.
            (*sub<mode>_1_slp): Ditto.
            (*and<mode>_1_slp): Ditto.
            (*<any_or:code><mode>_1_slp): Ditto.
            (*ashl<mode>3_1_slp): Ditto.
            (*<any_shiftrt:insn><mode>3_1_slp): Ditto.
            (*<any_rotate:insn><mode>3_1_slp): Ditto.
            (*neg<mode>_1_slp): New insn_and_split pattern.
            (*one_cmpl<mode>_1_slp): Ditto.

    gcc/testsuite/
            PR target/85730
            PR target/82524
            * gcc.target/i386/pr85730.c: New test.