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Subject: [Bug middle-end/104763] [12.0] Generate wrong assembly code
Date: Thu, 03 Mar 2022 05:08:24 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104763

--- Comment #3 from =E3=80=82 <570070308 at qq dot com> ---
(In reply to Jakub Jelinek from comment #2)
> Can't reproduce with -O2, with -O1 there are 2 stores instead of 3
> before the endless loop starting with
> r9-384-gf1bcb061d172ca7e3bdcc46476b20776382a2974

edit `+2` to `+7` then -O3 will be wrong too.

test.c:
```
#include <stddef.h>
#include <stdbool.h>
#include <stdint.h>
void move_up()
{
    for ( size_t* i=3D(size_t *)(0xb8000+160*24); ; )
    {
        *i=3D0x0700070007000700;
        if ( i =3D=3D (size_t *)(0xb8000+160*24)+7 )
        {
            break;
        }
        ++i;
    }
    while (1){}
}
```
assembly with -O3:
```
move_up:
.LFB0:
        .cfi_startproc
        endbr64
        movabsq $504410854964332288, %rax
        movq    %rax, 757512
        movq    %rax, 757520
        movq    %rax, 757528
        movq    %rax, 757536
        movq    %rax, 757544
        movq    %rax, 757552
        movq    %rax, 757560
.L2:
        jmp     .L2
        .cfi_endproc
```=