On Wed, Nov 12, 2014 at 01:11:40PM -0800, H.J. Lu wrote:
> On Wed, Nov 12, 2014 at 1:02 PM, Jakub Jelinek <[email protected]> wrote:
> > On Wed, Nov 12, 2014 at 12:43:17PM -0800, H.J. Lu wrote:
> >> @@ -42686,8 +42692,12 @@ x86_output_mi_thunk (FILE *file, tree,
> >> HOST_WIDE_INT delta,
> >> else
> >> {
> >> if (ix86_cmodel == CM_LARGE_PIC && SYMBOLIC_CONST (fnaddr))
> >> - fnaddr = legitimize_pic_address (fnaddr,
> >> - gen_rtx_REG (Pmode, tmp_regno));
> >> + {
> >> + SET_REGNO (pic_offset_table_rtx, R11_REG);
> >
> > If pic_offset_table_rtx has never been initialized, how you can use
>
> It is a pseudo PIC register which is uninitialized:
>
> (gdb) call debug_rtx (this_target_rtl->x_pic_offset_table_rtx)
> (reg:DI 89)
> (gdb)
>
> > SET_REGNO on it? Shouldn't that be pic_offset_table_rtx = gen_raw_REG
> > (Pmode, R11_REG);
>
> I added the following comments and am checking it into trunk:
>
> // CM_LARGE_PIC always uses pseudo PIC register which is
> // uninitialized. Since FUNCTION is local and calling it
> // doesn't go through PLT, we use scratch register %r11 as
> // PIC register and initialize it here.
>From what I can see, it probably in this case should be always non-NULL,
as it is initialized in init_emit_regs:
5847 if ((unsigned) PIC_OFFSET_TABLE_REGNUM != INVALID_REGNUM)
5848 pic_offset_table_rtx = gen_raw_REG (Pmode, PIC_OFFSET_TABLE_REGNUM);
5849 else
5850 pic_offset_table_rtx = NULL_RTX;
and as pic_offset_table_rtx is NULL there, PIC_OFFSET_TABLE_REGNUM is
BX_REG.
Later on, assign_params will change that to:
3684 if (targetm.use_pseudo_pic_reg ())
3685 pic_offset_table_rtx = gen_reg_rtx (Pmode);
and do_reload, after reload temporarily changing the REGNO, will overwrite
it again to the chosen pseudo:
5470 if (pic_offset_table_regno != INVALID_REGNUM)
5471 pic_offset_table_rtx = gen_rtx_REG (Pmode, pic_offset_table_regno);
So, all in all, SET_REGNO sounds inappropriate to me, everywhere else
gen_raw_REG or gen_rtx_REG is used instead, so IMNSHO you should do the
same.
Jakub
