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Subject: [Bug middle-end/98896] local label displaced with -O2
Date: Sat, 30 Jan 2021 11:25:06 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98896

--- Comment #6 from Stas Sergeev <stsp at users dot sourceforge.net> ---
(In reply to Jakub Jelinek from comment #5)
> I think Andrew meant asm goto, which you haven't tried.

You are right.
Thanks for mentioning that.
But it doesn't work as well:
---
int main(void)
{
    __label__ cont;
    asm volatile goto (
        "push %l[cont]\n"
        "ret\n"
    ::::cont);
cont:
    return 0;
}
---

$ LC_ALL=3DC cc -Wall -ggdb3 -O2 -o jmpret2 jmpret2.c -pie -fPIE
/usr/bin/ld: /tmp/cc1UoxnD.o: relocation R_X86_64_32S against `.text.startu=
p'
can not be used when making a PIE object; recompile with -fPIE


And in an asm file we see:
---
#APP
# 4 "jmpret2.c" 1
        push .L2        #
ret
---


Please compare this to the following:
---
int main(void)
{
    __label__ cont;
    asm volatile (
        "push %0\n"
        "ret\n"
    ::"r"(&&cont));
cont:
    return 0;
}
---

And its asm:
---
.L2:
        .loc 1 4 5 view .LVU1
        leaq    .L2(%rip), %rax #, tmp83
#APP
# 4 "jmpret3.c" 1
        push %rax       # tmp83
ret
---


So... it seems, only the second case can work,
and indeed does with clang?=