[MIPS] cannot split restore_gp

[Fu, Chao-Ying]

Hi,

  G++ could not split restore_gp.
Please check this test (from #line 15017 "configure" of
gcc/libstdc++-v3/).

# cat foo.cpp
struct S { ~S(); };
void bar();
void foo()
{
  S s;
  bar();
}

# ~/dev/gcc45/build/gcc/cc1plus -quiet foo.cpp -o foo.s -mno-shared -mplt 
-mabicalls -G0
foo.cpp: In function â?~foo()â?T:
foo.cpp:7:1: error: could not split insn
(insn 29 28 30 (parallel [
(set (reg:SI 28 $28)
(unspec_volatile:SI [
(const_int 0 [0x0])
] 7))
(clobber (reg:SI 2 $2))
]) 555 {restore_gp} (nil))
foo.cpp:7:1: internal compiler error: in final_scan_insn, at final.c:2651
Please submit a full bug report,
with preprocessed source if appropriate.
See  for instructions.

--

  Something may be wrong before we reach the "final" pass.
(Or, we should have split restore_gp earlier.)
Any idea?  Thanks!

Regards,
Chao-ying

Re: [MIPS] cannot split restore_gp

[Richard Sandiford]

"Fu, Chao-Ying"  writes:
> Hi,
>
>   G++ could not split restore_gp.
> Please check this test (from #line 15017 "configure" of
> gcc/libstdc++-v3/).
>
> # cat foo.cpp
> struct S { ~S(); };
> void bar();
> void foo()
> {
>   S s;
>   bar();
> }
>
> # ~/dev/gcc45/build/gcc/cc1plus -quiet foo.cpp -o foo.s -mno-shared -mplt 
> -mabicalls -G0
> foo.cpp: In function â?~foo()â?T:
> foo.cpp:7:1: error: could not split insn
> (insn 29 28 30 (parallel [
> (set (reg:SI 28 $28)
> (unspec_volatile:SI [
> (const_int 0 [0x0])
> ] 7))
> (clobber (reg:SI 2 $2))
> ]) 555 {restore_gp} (nil))
> foo.cpp:7:1: internal compiler error: in final_scan_insn, at final.c:2651
> Please submit a full bug report,
> with preprocessed source if appropriate.
> See  for instructions.
>
> --
>
>   Something may be wrong before we reach the "final" pass.
> (Or, we should have split restore_gp earlier.)
> Any idea?  Thanks!

It's another case of splits-to-nothing being misinterpreted as failed
splits.  The patch below fixes the testcase, and although this particular
testcase probably passes on 4.4, the same patch is needed there.
I'll test it over the next few days.

Richard


Index: gcc/config/mips/mips.c
===
--- gcc/config/mips/mips.c  (revision 153036)
+++ gcc/config/mips/mips.c  (working copy)
@@ -9533,7 +9533,10 @@
   gcc_assert (TARGET_ABICALLS && TARGET_OLDABI && epilogue_completed);
 
   if (!cfun->machine->must_restore_gp_when_clobbered_p)
-return;
+{
+  emit_note (NOTE_INSN_DELETED);
+  return;
+}
 
   if (TARGET_MIPS16)
 {