[Bug gas/22874] New: GAS does not emit multibyte nops before a function symbol

[mliska at suse dot cz]

https://sourceware.org/bugzilla/show_bug.cgi?id=22874

            Bug ID: 22874
           Summary: GAS does not emit multibyte nops before a function
                    symbol
           Product: binutils
           Version: 2.31 (HEAD)
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: gas
          Assignee: unassigned at sourceware dot org
          Reporter: mliska at suse dot cz
  Target Milestone: ---

$ cat nops.c
void
__attribute__((aligned(128)))
foo (int invariant)
{
  for (;;)
    ;
}

void
__attribute__((aligned(64)))
foo2 (int invariant)
{
}


int main() {}

$ gcc nops.c -O2
$ objdump -S a.out
[snip]
00000000004004b0 <__do_global_dtors_aux>:
  4004b0:       80 3d 71 0b 20 00 00    cmpb   $0x0,0x200b71(%rip)        #
601028 <__TMC_END__>
  4004b7:       75 17                   jne    4004d0
<__do_global_dtors_aux+0x20>
  4004b9:       55                      push   %rbp
  4004ba:       48 89 e5                mov    %rsp,%rbp
  4004bd:       e8 7e ff ff ff          callq  400440 <deregister_tm_clones>
  4004c2:       c6 05 5f 0b 20 00 01    movb   $0x1,0x200b5f(%rip)        #
601028 <__TMC_END__>
  4004c9:       5d                      pop    %rbp
  4004ca:       c3                      retq   
  4004cb:       0f 1f 44 00 00          nopl   0x0(%rax,%rax,1)
  4004d0:       f3 c3                   repz retq 
  4004d2:       0f 1f 40 00             nopl   0x0(%rax)
  4004d6:       66 2e 0f 1f 84 00 00    nopw   %cs:0x0(%rax,%rax,1)
  4004dd:       00 00 00 

00000000004004e0 <frame_dummy>:
  4004e0:       55                      push   %rbp
  4004e1:       48 89 e5                mov    %rsp,%rbp
  4004e4:       5d                      pop    %rbp
  4004e5:       eb 89                   jmp    400470 <register_tm_clones>
  4004e7:       66 2e 0f 1f 84 00 00    nopw   %cs:0x0(%rax,%rax,1)
  4004ee:       00 00 00 
  4004f1:       66 2e 0f 1f 84 00 00    nopw   %cs:0x0(%rax,%rax,1)
  4004f8:       00 00 00 
  4004fb:       0f 1f 44 00 00          nopl   0x0(%rax,%rax,1)

0000000000400500 <foo>:
  400500:       eb fe                   jmp    400500 <foo>
  400502:       90                      nop
  400503:       90                      nop
  400504:       90                      nop
  400505:       90                      nop
  400506:       90                      nop
  400507:       90                      nop
  400508:       90                      nop
  400509:       90                      nop
  40050a:       90                      nop
  40050b:       90                      nop
  40050c:       90                      nop
  40050d:       90                      nop
  40050e:       90                      nop
  40050f:       90                      nop
  400510:       90                      nop
  400511:       90                      nop
  400512:       90                      nop
  400513:       90                      nop
  400514:       90                      nop
  400515:       90                      nop
  400516:       90                      nop
  400517:       90                      nop
  400518:       90                      nop
  400519:       90                      nop
  40051a:       90                      nop
  40051b:       90                      nop
  40051c:       90                      nop
  40051d:       90                      nop
  40051e:       90                      nop
  40051f:       90                      nop
  400520:       90                      nop
  400521:       90                      nop
  400522:       90                      nop
  400523:       90                      nop
  400524:       90                      nop
  400525:       90                      nop
  400526:       90                      nop
  400527:       90                      nop
  400528:       90                      nop
  400529:       90                      nop
  40052a:       90                      nop
  40052b:       90                      nop
  40052c:       90                      nop
  40052d:       90                      nop
  40052e:       90                      nop
  40052f:       90                      nop
  400530:       90                      nop
  400531:       90                      nop
  400532:       90                      nop
  400533:       90                      nop
  400534:       90                      nop
  400535:       90                      nop
  400536:       90                      nop
  400537:       90                      nop
  400538:       90                      nop
  400539:       90                      nop
  40053a:       90                      nop
  40053b:       90                      nop
  40053c:       90                      nop
  40053d:       90                      nop
  40053e:       90                      nop
  40053f:       90                      nop

0000000000400540 <foo2>:
  400540:       f3 c3                   repz retq 
  400542:       66 2e 0f 1f 84 00 00    nopw   %cs:0x0(%rax,%rax,1)
  400549:       00 00 00 
  40054c:       0f 1f 40 00             nopl   0x0(%rax)
[snip]

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