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From: "hjl.tools at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/106022] New: [12/13 Regression] Enable vectorizer
 generates extra load
Date: Fri, 17 Jun 2022 21:59:49 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106022

            Bug ID: 106022
           Summary: [12/13 Regression] Enable vectorizer generates extra
                    load
           Product: gcc
           Version: 12.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hjl.tools at gmail dot com
                CC: crazylht at gmail dot com
  Target Milestone: ---

[hjl@gnu-clx-1 gcc-bisect]$ cat x.c
void foo(char * c) {
    c[0] =3D 0;
    c[1] =3D 1;
    c[2] =3D 2;
    c[3] =3D 3;
}
[hjl@gnu-clx-1 gcc-bisect]$ gcc -O3 x.c -S
[hjl@gnu-clx-1 gcc-bisect]$ cat x.s=20
        .file   "x.c"
        .text
        .p2align 4
        .globl  foo
        .type   foo, @function
foo:
.LFB0:
        .cfi_startproc
        movl    .LC0(%rip), %eax
        movl    %eax, (%rdi)
        ret
        .cfi_endproc
.LFE0:
        .size   foo, .-foo
        .section        .rodata.cst4,"aM",@progbits,4
        .align 4
.LC0:
        .byte   0
        .byte   1
        .byte   2
        .byte   3
        .ident  "GCC: (GNU) 12.1.1 20220507 (Red Hat 12.1.1-1)"
        .section        .note.GNU-stack,"",@progbits
[hjl@gnu-clx-1 gcc-bisect]$ gcc -O3 x.c -S -fno-tree-vectorize
[hjl@gnu-clx-1 gcc-bisect]$ cat x.s
        .file   "x.c"
        .text
        .p2align 4
        .globl  foo
        .type   foo, @function
foo:
.LFB0:
        .cfi_startproc
        movl    $50462976, (%rdi)
        ret
        .cfi_endproc
.LFE0:
        .size   foo, .-foo
        .ident  "GCC: (GNU) 12.1.1 20220507 (Red Hat 12.1.1-1)"
        .section        .note.GNU-stack,"",@progbits
[hjl@gnu-clx-1 gcc-bisect]$ /usr/gcc-11.2.1-x32/bin/gcc -S -O3 x.c=20
[hjl@gnu-clx-1 gcc-bisect]$ cat x.s
        .file   "x.c"
        .text
        .p2align 4
        .globl  foo
        .type   foo, @function
foo:
.LFB0:
        .cfi_startproc
        movl    $50462976, (%rdi)
        ret
        .cfi_endproc
.LFE0:
        .size   foo, .-foo
        .ident  "GCC: (GNU) 11.2.1 20220118"
        .section        .note.GNU-stack,"",@progbits
[hjl@gnu-clx-1 gcc-bisect]$=