[Bug inline-asm/101727] New: invalid symbol redefinition when -O2 enabled

[Bug inline-asm/101727] New: invalid symbol redefinition when -O2 enabled

[zhan3299 at purdue dot edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101727

            Bug ID: 101727
           Summary: invalid symbol redefinition when -O2 enabled
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: inline-asm
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zhan3299 at purdue dot edu
  Target Milestone: ---

Following code can be successfully compiled with O0 optimization enabled, but
not O2.

Example code:
---
#include <stdio.h>

int func() {
    int filter;
    asm volatile(
        "  leaq _filter(%%rip), %%rax\n"
        "  jmp _out\n"
        "_filter:\n"
        ".ascii \"\\040\"\n"
        "_out:"
        : "=rax"(filter)
        :
        :);
    return filter;
}
int main() {
    printf("%#x", func());
    return 0;
}
---

Error messages of O2:
---
ASM generation compiler returned: 0
<source>: Assembler messages:
<source>:7: Error: symbol `_filter' is already defined
<source>:9: Error: symbol `_out' is already defined
Execution build compiler returned: 1
---

It affects 11.0, 12.0.

O2: https://godbolt.org/z/j9xG96fxW
O0: https://godbolt.org/z/b4TqddvYh

[Bug inline-asm/101727] invalid symbol redefinition when -O2 enabled

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101727

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |INVALID
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Inline-asm can be copied, If you need labels inside them you need to use
something different.


Also I really doubt "=rax" is the correct constraint you want.  Please read
https://gcc.gnu.org/onlinedocs/gcc-11.2.0/gcc/Constraints.html#Constraints

[Bug inline-asm/101727] invalid symbol redefinition when -O2 enabled

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101727

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Note, the documentation talks about it:
https://gcc.gnu.org/onlinedocs/gcc-11.2.0/gcc/Basic-Asm.html#Basic-Asm
Under certain circumstances, GCC may duplicate (or remove duplicates of) your
assembly code when optimizing. This can lead to unexpected duplicate symbol
errors during compilation if your assembly code defines symbols or labels.
and
https://gcc.gnu.org/onlinedocs/gcc-11.2.0/gcc/Extended-Asm.html#Extended-Asm
Under certain circumstances, GCC may duplicate (or remove duplicates of) your
assembly code when optimizing. This can lead to unexpected duplicate symbol
errors during compilation if your asm code defines symbols or labels. Using
‘%=’ (see AssemblerTemplate) may help resolve this problem.
Normally people use numbered labels instead (leal 1f(...); ... 1: ...) or one
can use %=.

[Bug inline-asm/101727] invalid symbol redefinition when -O2 enabled

[zhan3299 at purdue dot edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101727

--- Comment #3 from zhan3299 at purdue dot edu ---
(In reply to Jakub Jelinek from comment #2)
> Note, the documentation talks about it:
> https://gcc.gnu.org/onlinedocs/gcc-11.2.0/gcc/Basic-Asm.html#Basic-Asm
> Under certain circumstances, GCC may duplicate (or remove duplicates of)
> your assembly code when optimizing. This can lead to unexpected duplicate
> symbol errors during compilation if your assembly code defines symbols or
> labels.
> and
> https://gcc.gnu.org/onlinedocs/gcc-11.2.0/gcc/Extended-Asm.html#Extended-Asm
> Under certain circumstances, GCC may duplicate (or remove duplicates of)
> your assembly code when optimizing. This can lead to unexpected duplicate
> symbol errors during compilation if your asm code defines symbols or labels.
> Using ‘%=’ (see AssemblerTemplate) may help resolve this problem.
> Normally people use numbered labels instead (leal 1f(...); ... 1: ...) or
> one can use %=.

Thanks for letting me know. I do apologize that I haven't gone through the
whole document and bothering you by this invalid issue. Sorry about it.