[Bug tree-optimization/125405] Missed optimization: mask/sub sign-extension idiom not canonicalized to sign extension

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125405

--- Comment #7 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jeff Law <law@gcc.gnu.org>:

https://gcc.gnu.org/g:c05164c348242b00b33cdf2988cc5e93d29b0478

commit r17-1680-gc05164c348242b00b33cdf2988cc5e93d29b0478
Author: Milan Tripkovic <Milan.Tripkovic@rt-rk.com>
Date:   Thu Jun 18 17:51:59 2026 -0600

    [PATCH] PR tree-optimization/125405: Missed optimization: mask/sub
sign-extension idiom not canonicalized to sign extension

    This patch implement new pattern for match.pd that recognize the
    sign-extension idiom (x & low_bits) - (x & sign_bit) and tests that covers
it.
    Pattern is based on conversation from bug report.

    TRUNK riscv output:
     sext8_hd:
              andi    a5,a0,127
              andi    a0,a0,128
              sub     a0,a5,a0
              ret

     sext16_hd:
              slli    a5,a0,49
              li      a4,32768
              srli    a5,a5,49
              and     a0,a0,a4
              sub     a0,a5,a0
              ret

    NEW riscv output:
    sext8_hd:
            slliw   a0,a0,24
            sraiw   a0,a0,24
            ret

    sext16_hd:
            slliw   a0,a0,16
            sraiw   a0,a0,16
            ret

    TRUNK x86 output:
    "sext8_hd":
            mov     rax, rdi
            and     edi, 128
            and     eax, 127
            sub     rax, rdi
            ret

    "sext16_hd":
            mov     rax, rdi
            and     edi, 32768
            and     eax, 32767
            sub     rax, rdi
            ret

    new x86 output:
    sext8_hd:
            movsbq  %dil, %rax
            ret

    sext16_hd:
            movswq  %di, %rax
            ret

            PR target/125405

    gcc/ChangeLog:

            * match.pd: New pattern added.

    gcc/testsuite/ChangeLog:

            * gcc.dg/pr125405-bitint.c: New test.
            * gcc.dg/tree-ssa/pr125405.c: New test.
            * gcc.target/riscv/pr125405.c: New test.