On Thu, May 21, 2015 at 12:32 PM, Alexander Monakov <amona...@ispras.ru> wrote:
> On Thu, 21 May 2015, H.J. Lu wrote:
>> On Thu, May 21, 2015 at 12:06 PM, Richard Henderson <r...@redhat.com> wrote:
>> > On 05/21/2015 12:01 PM, H.J. Lu wrote:
>> >> +++ b/gcc/testsuite/gcc.target/i386/pr66232-1.c
>> >> @@ -0,0 +1,13 @@
>> >> +/* { dg-do compile { target *-*-linux* } } */
>> >> +/* { dg-options "-O2 -fpic -fno-plt" } */
>> >> +
>> >> +extern void bar (void);
>> >> +
>> >> +void
>> >> +foo (void)
>> >> +{
>> >> + bar ();
>> >> +}
>> >> +
>> >> +/* { dg-final { scan-assembler "jmp\[ \t\]*.bar@GOTPCREL" { target { !
>> >> ia32 } } } } */
>> >> +/* { dg-final { scan-assembler "call\[ \t\]*.bar@GOT\\(" { target ia32 }
>> >> } } */
>> >
>> > Do you really want to check for no tail call for ia32 here?
>> > That's really just a missed optimization, surely.
>> >
>> >
>>
>> I'd like to keep it. When it is fixed, we can update it. I tried:
>>
>> https://gcc.gnu.org/ml/gcc-patches/2015-05/msg00230.html
>>
>> and got
>>
>> call __x86.get_pc_thunk.ax
>> addl $_GLOBAL_OFFSET_TABLE_, %eax
>> subl $28, %esp
>> .cfi_def_cfa_offset 32
>> movl bar@GOT(%eax), %eax
>> movl %eax, 12(%esp)
>> addl $28, %esp
>> .cfi_def_cfa_offset 4
>> jmp *%eax
>>
>> This is very odd code, comparing against
>
> To avoid that, you need the CLOBBERED_REGS patch too:
> https://gcc.gnu.org/ml/gcc-patches/2015-05/msg00227.html
>
Should both patches be needed for ia32 tail call?
--
H.J.
