[Bug rtl-optimization/33669] [4.3 Regression] Revision 128957 miscompiles 481.wrf

["zadeck at naturalbridge dot com" <gcc-bugzilla@gcc.gnu.org>]

------- Comment #9 from zadeck at naturalbridge dot com  2007-10-07 03:18 -------
Subject: Re:  [4.3 Regression]  Revision 128957
 miscompiles 481.wrf

hj,

here is a fix.  I will most likely post the patch on monday after i get
it really tested on a bunch of platforms.  The fix is in the third
stanza, the rest is better logging.

The failure only happens if you have a block with 2 or more uses of a
multiword pseudo register that is local to this block and has been
allocated by local_alloc.  The uses must be in a particular form: the
last use was a subreg use that only used some of the hard registers and
a previous non subreg use of the multiword register.

When all of this happens, the code did not properly expand this to a
whole multiregister when the second to last use is encounterd in the
backwards scan.

I.e. a lot of things have to happen to get this to fail.

Thanks for the small test case, that really helped.

Kenny



Index: ra-conflict.c
===================================================================
--- ra-conflict.c    (revision 129036)
+++ ra-conflict.c    (working copy)
@@ -76,7 +76,7 @@ record_one_conflict_between_regnos (enum
                     enum machine_mode mode2, int r2)
 {
   if (dump_file)
-    fprintf (dump_file, "  rocbr adding %d<=>%d\n", r1, r2);
+    fprintf (dump_file, "    rocbr adding %d<=>%d\n", r1, r2);
   if (reg_allocno[r1] >= 0 && reg_allocno[r2] >= 0)
     {
       int tr1 = reg_allocno[r1];
@@ -293,9 +293,6 @@ set_conflicts_for_earlyclobber (rtx insn
                             recog_data.operand[use + 1]);
         }
     }
-
-  if (dump_file)
-    fprintf (dump_file, "  finished early clobber conflicts.\n");
 }


@@ -876,7 +873,7 @@ global_conflicts (void)
                         allocnum, renumber);
             }

-          else if (GET_ALLOCNO_LIVE (allocnos_live, allocnum) == 0)
+          else
             {
               if (dump_file)
             fprintf (dump_file, "    dying pseudo\n");
@@ -963,6 +960,8 @@ global_conflicts (void)
          FIXME: We should consider either adding a new kind of
          clobber, or adding a flag to the clobber distinguish
          these two cases.  */
+          if (dump_file && VEC_length (df_ref_t, clobbers))
+        fprintf (dump_file, "  clobber conflicts\n");
           for (k = VEC_length (df_ref_t, clobbers) - 1; k >= 0; k--)
         {
           struct df_ref *def = VEC_index (df_ref_t, clobbers, k);
@@ -1024,6 +1023,8 @@ global_conflicts (void)
           if (GET_CODE (PATTERN (insn)) == PARALLEL && multiple_sets
(insn))
         {
           int j;
+          if (dump_file)
+            fprintf (dump_file, "  multiple sets\n");
           for (j = VEC_length (df_ref_t, dying_regs) - 1; j >= 0; j--)
             {
               int used_in_output = 0;


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33669