[Bug target/51784] PIC register not correctly preserved in nested funcs / with non-local goto

["iains at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51784

--- Comment #36 from Iain Sandoe <iains at gcc dot gnu.org> 2012-01-18 13:47:36 UTC ---
(In reply to comment #34)

> 5) to determine if you need to load the pic register or not, you should match
> what
> the prologue expansion does, try
> (pic_offset_table_rtx
>       && (df_regs_ever_live_p (REAL_PIC_OFFSET_TABLE_REGNUM)
>           || crtl->profile))

nothing seems to use df_regs_ever_live_p in the md files, and the function is
not visible.  I also wonder if it is updated during RTL optimization?

(I tried making a function in i386.c that performed these tests and was visible
from the md - but it didn't work).

For now, I've used crtl->uses_pic_offset_table which seems to work.

Is there any other suggestion?

> probably also anded with && !current_function_is_leaf - non-local goto receiver
> in leaf functions doesn't make much sense and certainly doesn't need to restore
> PIC pointer, plus it will simplify it (for leaf functions we sometimes decide
> to use a different register as pic pointer instead of %ebx).

hopefully using pic_offset_table_rtx will pick up the current one?