http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12306
--- Comment #4 from Kazumoto Kojima <kkojima at gcc dot gnu.org> ---
(In reply to Oleg Endo from comment #3)
> If I understand correctly, rebuilding the GOT pointer in r12 is necessary at
> function entry, since it is generally not known if r12 is a valid GOT
> pointer at function entry when mixing PIC code and non-PIC code. Calling a
> PIC function from a non-PIC function could result in a clobbered GOT >
Yep. If a pic function is called from a pic function, that
save&restore can be removed. The case like
non_pic_function:
mov.l r12,@-r15
sts.l pr,@-r15
<use r12 as a variable x>
<call PIC function here (r12 should not be clobbered)>
<use r12 as a variable x>
lds.l @r15+,pr
rts
mov.l @r15+,r12
needs it. If we knew that that pic function can't be called from
any non-pic functions by some additional information, we could
optimize the code with removing that save&restore r12.
