[RFC] Fix PR rtl-optimization/33732

[Rask Ingemann Lambertsen]

On Wed, Nov 07, 2007 at 09:34:41PM -0500, Kenneth Zadeck wrote:
> John David Anglin wrote:
> >
> > Breaks ada build in stage2.  Turning off ada, I see
> >
> > /test/gnu/gcc/objdir/./prev-gcc/xgcc -B/test/gnu/gcc/objdir/./prev-gcc/ -B/opt/g
> > nu/gcc/gcc-4.3.0/hppa2.0w-hp-hpux11.11/bin/ -c   -g -O2 -DIN_GCC   -W -Wall -Wwr
> > ite-strings -Wstrict-prototypes -Wmissing-prototypes -Wold-style-definition -Wmi
> > ssing-format-attribute -pedantic -Wno-long-long -Wno-variadic-macros
> >                      -Wno-overlength-strings -Werror -fno-common   -DHAVE_CONFIG_H -I. -I. -I../../gcc/gcc -I../../gcc/gcc/. -I../../gcc/gcc/../include -I../../gcc/gcc/../libcpp/include -I/opt/gnu/gcc/gcc-4.3.0/include -I/opt/gnu/gcc/gcc-4.3.0/include -I../../gcc/gcc/../libdecnumber -I../../gcc/gcc/../libdecnumber/dpd -I../libdecnumber    ../../gcc/gcc/local-alloc.c -o local-alloc.o
> > ../../gcc/gcc/local-alloc.c: In function 'find_free_reg':
> > ../../gcc/gcc/local-alloc.c:2350: internal compiler error: in df_reg_chain_unlink, at df-scan.c:795
> >
> The kinds of errors that i saw were not being able to get a register
> very late in reload as well as inconsistencies between the number of
> words being reserved for the stack and the number of slots actually
> being used by reload. 
> 
> This bug is new, but not at all surprising.

   To me it _is_ surpricing to see an ICE just because of one more complete
rescan of all insns.

   It looks like a simple DF bug of not keeping the DF_HARD_REG_LIVE flag
up-to-date when the register changes in a df_ref. Reload changes a regno
from a hard reg back to a pseudo reg, but DF forgets to update the flag.
Does this look right?

Index: gcc/df-scan.c
===================================================================
--- gcc/df-scan.c	(revision 129849)
+++ gcc/df-scan.c	(working copy)
@@ -1839,6 +1839,33 @@ df_insn_change_bb (rtx insn)
       fprintf (dump_file, "  to %d\n", new_bb->index);
 }
 
+/* Update the DF_HARD_REG_LIVE flag of THIS_REF.  */
+
+static void
+df_update_hard_reg_live_flag (struct df_ref *this_ref)
+{
+  unsigned int regno = DF_REF_REGNO (this_ref);
+
+  /* We need to clear this bit because fwprop, and in the future
+     possibly other optimizations sometimes create new refs using ond
+     refs as the model.  */
+  DF_REF_FLAGS_CLEAR (this_ref, DF_HARD_REG_LIVE);
+
+  /* See if this ref needs to have DF_HARD_REG_LIVE bit set.  */
+  if (HARD_REGISTER_NUM_P (regno) 
+      && (!DF_REF_IS_ARTIFICIAL (this_ref)))
+    {
+      if (DF_REF_TYPE (this_ref) == DF_REF_REG_DEF)
+	{
+	  if (!DF_REF_FLAGS_IS_SET (this_ref, DF_REF_MAY_CLOBBER))
+	    DF_REF_FLAGS_SET (this_ref, DF_HARD_REG_LIVE);
+	}
+      else if (!(TEST_HARD_REG_BIT (elim_reg_set, regno)
+		 && (regno == FRAME_POINTER_REGNUM
+		     || regno == ARG_POINTER_REGNUM)))
+	DF_REF_FLAGS_SET (this_ref, DF_HARD_REG_LIVE);
+    }
+}
 
 /* Helper function for df_ref_change_reg_with_loc.  */
 
@@ -1859,6 +1886,7 @@ df_ref_change_reg_with_loc_1 (struct df_
 
 	  DF_REF_REGNO (the_ref) = new_regno;
 	  DF_REF_REG (the_ref) = regno_reg_rtx[new_regno];
+	  df_update_hard_reg_live_flag (the_ref);
 
 	  /* Pull the_ref out of the old regno chain.  */
 	  if (prev_ref)
@@ -2584,26 +2612,7 @@ df_ref_create_structure (struct df_colle
   DF_REF_NEXT_REG (this_ref) = NULL;
   DF_REF_PREV_REG (this_ref) = NULL;
   DF_REF_ORDER (this_ref) = df->ref_order++;
-
-  /* We need to clear this bit because fwprop, and in the future
-     possibly other optimizations sometimes create new refs using ond
-     refs as the model.  */
-  DF_REF_FLAGS_CLEAR (this_ref, DF_HARD_REG_LIVE);
-
-  /* See if this ref needs to have DF_HARD_REG_LIVE bit set.  */
-  if ((regno < FIRST_PSEUDO_REGISTER) 
-      && (!DF_REF_IS_ARTIFICIAL (this_ref)))
-    {
-      if (DF_REF_TYPE (this_ref) == DF_REF_REG_DEF)
-	{
-	  if (!DF_REF_FLAGS_IS_SET (this_ref, DF_REF_MAY_CLOBBER))
-	    DF_REF_FLAGS_SET (this_ref, DF_HARD_REG_LIVE);
-	}
-      else if (!(TEST_HARD_REG_BIT (elim_reg_set, regno)
-		 && (regno == FRAME_POINTER_REGNUM
-		     || regno == ARG_POINTER_REGNUM)))
-	DF_REF_FLAGS_SET (this_ref, DF_HARD_REG_LIVE);
-    }
+  df_update_hard_reg_live_flag (this_ref);
 
   if (collection_rec)
     {

-- 
Rask Ingemann Lambertsen
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