[Bug rtl-optimization/46598] [4.4/4.5/4.6 Regression] Miscompiles computed goto

["hjl.tools at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46598

--- Comment #16 from H.J. Lu <hjl.tools at gmail dot com> 2010-11-23 15:44:35 UTC ---
(In reply to comment #14)
> (In reply to comment #13)
> > They can use the new rdtsc builtin.
> 
> In which GCC version will it appear ? will be cool if you can share a little
> example as well.

GCC 4.5 supports it:

[hjl@gnu-6 tmp]$ cat x.c
#include <x86intrin.h>

unsigned long long
foo ()
{
  return __rdtsc ();
}
[hjl@gnu-6 tmp]$ gcc -O2 x.c -S
[hjl@gnu-6 tmp]$ cat x.s
    .file    "x.c"
    .text
    .p2align 4,,15
.globl foo
    .type    foo, @function
foo:
.LFB535:
    .cfi_startproc
    rdtsc
    salq    $32, %rdx
    orq    %rdx, %rax
    ret
    .cfi_endproc
.LFE535:
    .size    foo, .-foo
    .ident    "GCC: (GNU) 4.5.1 20100924 (Red Hat 4.5.1-4)"
    .section    .note.GNU-stack,"",@progbits
[hjl@gnu-6 tmp]$ gcc -O2 x.c -S -m32
[hjl@gnu-6 tmp]$ cat x.s
    .file    "x.c"
    .text
    .p2align 4,,15
.globl foo
    .type    foo, @function
foo:
    pushl    %ebp
    movl    %esp, %ebp
    rdtsc
    popl    %ebp
    ret
    .size    foo, .-foo
    .ident    "GCC: (GNU) 4.5.1 20100924 (Red Hat 4.5.1-4)"
    .section    .note.GNU-stack,"",@progbits
[hjl@gnu-6 tmp]$