loop-iv.c (replace_single_def_regs): Look for REG_EQUAL notes...

	* loop-iv.c (replace_single_def_regs): Look for REG_EQUAL notes;
	follow chains of regs with a single definition, and allow expressions
	that are function_invariant_p.

From-SVN: r146700

gcc/ChangeLog

+2009-04-24  Bernd Schmidt  <bernd.schmidt@analog.com>
+
+	* loop-iv.c (replace_single_def_regs): Look for REG_EQUAL notes;
+	follow chains of regs with a single definition, and allow expressions
+	that are function_invariant_p.
+
 2009-04-24  Paolo Bonzini  <bonzini@gnu.org>
 
 	PR middle-end/39867

gcc/loop-iv.c

@@ -1376,23 +1376,46 @@ replace_single_def_regs (rtx *reg, void *expr1)
 {
   unsigned regno;
   df_ref adef;
-  rtx set;
+  rtx set, src;
   rtx *expr = (rtx *)expr1;
 
   if (!REG_P (*reg))
     return 0;
 
   regno = REGNO (*reg);
-  adef = DF_REG_DEF_CHAIN (regno);
-  if (adef == NULL || DF_REF_NEXT_REG (adef) != NULL
-      || DF_REF_IS_ARTIFICIAL (adef))
-    return -1;
+  for (;;)
+    {
+      rtx note;
+      adef = DF_REG_DEF_CHAIN (regno);
+      if (adef == NULL || DF_REF_NEXT_REG (adef) != NULL
+	    || DF_REF_IS_ARTIFICIAL (adef))
+	return -1;
+
+      set = single_set (DF_REF_INSN (adef));
+      if (set == NULL || !REG_P (SET_DEST (set))
+	  || REGNO (SET_DEST (set)) != regno)
+	return -1;
 
-  set = single_set (DF_REF_INSN (adef));
-  if (set == NULL || SET_DEST (set) != *reg || !CONSTANT_P (SET_SRC (set)))
+      note = find_reg_equal_equiv_note (DF_REF_INSN (adef));
+
+      if (note && function_invariant_p (XEXP (note, 0)))
+	{
+	  src = XEXP (note, 0);
+	  break;
+	}
+      src = SET_SRC (set);
+
+      if (REG_P (src))
+	{
+	  regno = REGNO (src);
+	  continue;
+	}
+      break;
+    }
+  if (!function_invariant_p (src))
     return -1;
 
-  *expr = simplify_replace_rtx (*expr, *reg, SET_SRC (set));
+  *expr = simplify_replace_rtx (*expr, *reg, src);
   return 1;
 }