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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/107404] [12/13 Regression] Wrong code with -O3 since
 r12-6416-g037cc0b4a6646cc8
Date: Thu, 03 Nov 2022 16:13:15 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107404

--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Uros Bizjak <uros@gcc.gnu.or=
g>:

https://gcc.gnu.org/g:35e8b889af144faad074c0fceed0390143ec37dd

commit r12-8890-g35e8b889af144faad074c0fceed0390143ec37dd
Author: Uros Bizjak <ubizjak@gmail.com>
Date:   Thu Nov 3 14:17:42 2022 +0100

    i386: Fix uninitialized register after peephole2 conversion [PR107404]

    The eliminate reg-reg move by inverting the condition of
    a cmove #2 peephole2 converts the following sequence:

      473: bx:DI=3D[r14:DI*0x8+r12:DI]
      960: r15:DI=3Dr8:DI
      485: {flags:CCC=3Dcmp(r15:DI+bx:DI,bx:DI);r15:DI=3Dr15:DI+bx:DI;}
      737: r15:DI=3D{(geu(flags:CCC,0))?r15:DI:bx:DI}

    to:

     1110: {flags:CCC=3Dcmp(r8:DI+bx:DI,bx:DI);r8:DI=3Dr8:DI+bx:DI;}
     1111: r15:DI=3D[r14:DI*0x8+r12:DI]
     1112: r15:DI=3D{(geu(flags:CCC,0))?r8:DI:r15:DI}

    Please note that(insn 1110) uses register BX, but its
    initialization was eliminated.

    Avoid conversion if eliminated move intialized a register, used
    in the moved instruction.

    2022-11-03  Uro=C3=85=C2=A1 Bizjak  <ubizjak@gmail.com>

    gcc/ChangeLog:

            PR target/107404
            * config/i386/i386.md (eliminate reg-reg move by inverting the
            condition of a cmove #2 peephole2): Check if eliminated move
            initialized a register, used in the moved instruction.

    gcc/testsuite/ChangeLog:

            PR target/107404
            * g++.target/i386/pr107404.C: New test.

    (cherry picked from commit 553b1d3dd5b9253ebdf66ee3260c717d5b807dd1)=