[Bug middle-end/23756] Missed optimization for PIC code with internal visibility

[christophe dot guillon at st dot com]

------- Comment #2 from christophe dot guillon at st dot com  2010-01-28 14:55 -------
This enhancement is still pending on gcc 4.4.3 on x86.
A function declared internal sets the GOT pointer while it could be avoided in
a callee-set-GOT model as on x86 ABI.
By defintion an internal function can only be accessed through functions of the
same module and thus, if the ABI forces the GOT pointer to be in ebx - which I
think is the case -, it does not have to be rematerialized.

See the original description also.
Compile the attached internal.c file with:
$ gcc -O3 -S -fpic internal.c

Check the .s file:
        .type   f, @function
f:
        call    __i686.get_pc_thunk.cx
        addl    $_GLOBAL_OFFSET_TABLE_, %ecx

The GOT pointer is materialized in ecx while it is guaranteed to be available
in ebx as soon as f is actually internal.


-- 

christophe dot guillon at st dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |christophe dot guillon at st
                   |                            |dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23756