[Bug rtl-optimization/32636] [4.3 Regression] 25_algorithms/search_n/iterator.cc: miscompiled on hppa2.0w-hp-hpux11.11

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

------- Comment #35 from jakub at gcc dot gnu dot org  2007-12-11 21:28 -------
df_get_entry_block_def_set has this:
  /* Once the prologue has been generated, all of these registers
     should just show up in the first regular block.  */
  if (HAVE_prologue && epilogue_completed)
    {
      /* Defs for the callee saved registers are inserted so that the
         pushes have some defining location.  */
      for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
        if ((call_used_regs[i] == 0) && (df_regs_ever_live_p (i)))
          bitmap_set_bit (entry_block_defs, i);
    }
  else
    {
...
      r = targetm.calls.struct_value_rtx (current_function_decl, true);
      if (r && REG_P (r))
        bitmap_set_bit (entry_block_defs, REGNO (r));
    }

So, apparently struct_value_rtx is already considered, but only before
prologues/epilogues are inserted (or the arch doesn't HAVE_prologue).
On PA call_used_regs[28] != 0, so the comment "Once the prologue ..."
doesn't make sense for it, because the if part won't ever set %r28 in
entry_block_defs, even when it is needed.  I've tried:
--- df-scan.c.jj        2007-10-26 13:45:44.000000000 +0200
+++ df-scan.c   2007-12-11 22:24:21.000000000 +0100
@@ -3530,12 +3530,12 @@ df_get_entry_block_def_set (bitmap entry
       bitmap_set_bit (entry_block_defs, STATIC_CHAIN_REGNUM);
 #endif
 #endif
-      
-      r = targetm.calls.struct_value_rtx (current_function_decl, true);
-      if (r && REG_P (r))
-       bitmap_set_bit (entry_block_defs, REGNO (r));
     }

+  r = targetm.calls.struct_value_rtx (current_function_decl, true);
+  if (r && REG_P (r))
+    bitmap_set_bit (entry_block_defs, REGNO (r));
+
   if ((!reload_completed) || frame_pointer_needed)
     {
       /* Any reference to any pseudo before reload is a potential
patch and it indeed probably cures this testcase.  The diff in assembly is:
...
        comib,>= 0,%r24,L$0025
        stw %r4,-72(%r30)
        comib,= 1,%r24,L$0026
-       ldil LR'L$C0002,%r28
+       ldil LR'L$C0003,%r19
        stw %r7,-52(%r30)
        ldw 4(%r26),%r20
        ldo -112(%r30),%r25
        ldo -120(%r30),%r26
        stw %r20,-116(%r30)
        ldw 4(%r6),%r19
        ldw 0(%r3),%r20
        stw %r19,-108(%r30)
        stw %r20,-120(%r30)
        ldw 0(%r6),%r19
        .CALL ARGW0=GR,ARGW1=GR,ARGW2=GR,ARGW3=GR
        bl _Z4foo1I1DIiEPFbiiEET_S4_S4_iRKiT0_,%r2
        stw %r19,-112(%r30)
...
 L$0026:
-       ldil LR'L$C0003,%r19
+       ldil LR'L$C0002,%r28
        ldw 4(%r26),%r20
        ldo RR'L$C0002(%r28),%r9
        ldil LR'L$C0001,%r28
...
which looks promissing (though of course without access to PA I can't be sure
it works).


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32636