------- Comment #13 from dave at hiauly1 dot hia dot nrc dot ca 2007-06-15
20:05 -------
Subject: Re: [4.3 Regression] Bootstrap failure in stage1 on hppa*-*-*
> > We need to know that the return pointer (r2) is not used and that
> > the function is a leaf function (i.e., that the incoming value in
> > r2 is unchanged). Calls clobber r2.
> >
> > Dave
>
> Sounds like the following patch would work:
>
> diff -r 149399c845b5 gcc/config/pa/pa.c
> --- a/gcc/config/pa/pa.c Tue Jun 12 15:49:27 2007 -0700
> +++ b/gcc/config/pa/pa.c Wed Jun 13 18:37:17 2007 -0700
> @@ -4415,7 +4415,7 @@ hppa_can_use_return_insn_p (void)
> {
> return (reload_completed
> && (compute_frame_size (get_frame_size (), 0) ? 0 : 1)
> - && df_hard_reg_used_count (2) == 1
> + && DF_REG_DEF_COUNT (2) == 0
> && ! frame_pointer_needed);
> }
>
>
> This essentially checks if r2 is ever written within the function
> (including the calls since r2 is included in the CALL_USED_REGS).
Ok, I've found the problem. The code that outputs trivial returns
in function.c has changed and just outputs the return when optimize
and HAVE_RETURN are true. As a result, we are generating trivial
returns in cases when we shouldn't.
I think the solution is to rename the "return" pattern and let
the pa epilogue expander control the show. This is what I currently
have:
Index: config/pa/pa.md
===================================================================
--- config/pa/pa.md (revision 125747)
+++ config/pa/pa.md (working copy)
@@ -7345,11 +7345,11 @@
;; This can only be used in a leaf function, so we do
;; not need to use the PIC register when generating PIC code.
-(define_insn "return"
+(define_insn "trivial_return"
[(return)
(use (reg:SI 2))
(const_int 0)]
- "hppa_can_use_return_insn_p ()"
+ ""
"*
{
if (TARGET_PA_20)
@@ -7409,7 +7409,7 @@
/* Try to use the trivial return first. Else use the full
epilogue. */
if (hppa_can_use_return_insn_p ())
- emit_jump_insn (gen_return ());
+ emit_jump_insn (gen_trivial_return ());
else
{
rtx x;
Index: config/pa/pa.c
===================================================================
--- config/pa/pa.c (revision 125747)
+++ config/pa/pa.c (working copy)
@@ -47,6 +47,7 @@
#include "tm_p.h"
#include "target.h"
#include "target-def.h"
+#include "df.h"
/* Return nonzero if there is a bypass for the output of
OUT_INSN and the fp store IN_INSN. */
@@ -4413,9 +4414,9 @@
hppa_can_use_return_insn_p (void)
{
return (reload_completed
- && (compute_frame_size (get_frame_size (), 0) ? 0 : 1)
- && ! df_regs_ever_live_p (2)
- && ! frame_pointer_needed);
+ && DF_REG_DEF_COUNT (2) == 0
+ && !frame_pointer_needed
+ && (compute_frame_size (get_frame_size (), 0) ? 0 : 1));
}
void
The code still seems to be generating trivial returns. Full bootstrap
is in progress.
If this works, there's probably some minor cleanups that can be made.
hppa_can_use_return_insn_p() is only called by the epilogue expander
and it may be possible to move it there. I also think we can do away
with one of trivial_return and return_internal in pa.md.
Dave
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32296
