ssa.c (rename_insn_1): Rename uses of undefined registers to prevent confusion if/when...

        * ssa.c (rename_insn_1): Rename uses of undefined registers to
        prevent confusion if/when the register is defined.

From-SVN: r54002

gcc/ChangeLog

+2002-05-29  Chris Lattner  <sabre@nondot.org>
+
+        * ssa.c (rename_insn_1): Rename uses of undefined registers to
+        prevent confusion if/when the register is defined.
+
 2002-05-29  Hans-Peter Nilsson  <hp@axis.com>
 
 	PR target/6838

gcc/ssa.c

@@ -916,18 +916,26 @@ rename_insn_1 (ptr, data)
       }
 
     case REG:
-      if (CONVERT_REGISTER_TO_SSA_P (REGNO (x)) &&
-	  REGNO (x) < ssa_max_reg_num)
+      if (CONVERT_REGISTER_TO_SSA_P (REGNO (x))
+	  && REGNO (x) < ssa_max_reg_num)
 	{
 	  rtx new_reg = ssa_rename_to_lookup (x);
 
-	  if (new_reg != NULL_RTX && new_reg != RENAME_NO_RTX)
+	  if (new_reg != RENAME_NO_RTX)
 	    {
-	      if (GET_MODE (x) != GET_MODE (new_reg))
-		abort ();
-	      *ptr = new_reg;
+	      if (new_reg != NULL_RTX)
+		{
+		  if (GET_MODE (x) != GET_MODE (new_reg))
+		    abort ();
+		  *ptr = new_reg;
+		}
+	      else
+		{
+		  /* Undefined value used, rename it to a new pseudo register so
+		     that it cannot conflict with an existing register */
+		  *ptr = gen_reg_rtx (GET_MODE(x));
+		}
 	    }
-	  /* Else this is a use before a set.  Warn?  */
 	}
       return -1;