reload1.c (reload_cse_move2add): Don't turn an implicit truncation into a…

reload1.c (reload_cse_move2add): Don't turn an implicit truncation into a self-set in the narrow mode.

* reload1.c (reload_cse_move2add): Don't turn an implicit
truncation into a self-set in the narrow mode.

From-SVN: r66638

gcc/ChangeLog

+2003-05-09  Alexandre Oliva  <aoliva@redhat.com>
+
+	* reload1.c (reload_cse_move2add): Don't turn an implicit
+	truncation into a self-set in the narrow mode.
+
 2003-05-09  Richard Earnshaw  <rearnsha@arm.com>
 
 	* arm.md (clzsi2): The CLZ instruction is predicable.

gcc/reload1.c

@@ -9166,7 +9166,14 @@ reload_cse_move2add (first)
 		     value flag.  jump2 already knows how to get rid of
 		     no-op moves.  */
 		  if (new_src == const0_rtx)
-		    validate_change (insn, &SET_SRC (pat), reg, 0);
+		    {
+		      /* If the constants are different, this is a
+			 truncation, that, if turned into (set (reg)
+			 (reg)), would be discarded.  Maybe we should
+			 try a truncMN pattern?  */
+		      if (INTVAL (src) == reg_offset [regno])
+			validate_change (insn, &SET_SRC (pat), reg, 0);
+		    }
 		  else if (rtx_cost (new_src, PLUS) < rtx_cost (src, SET)
 			   && have_add2_insn (reg, new_src))
 		    {
@@ -9252,9 +9259,15 @@ reload_cse_move2add (first)
 		      int success = 0;
 
 		      if (new_src == const0_rtx)
-			/* See above why we create (set (reg) (reg)) here.  */
-			success
-			  = validate_change (next, &SET_SRC (set), reg, 0);
+			{
+			  if (INTVAL (src) == reg_offset [regno])
+			    /* See above why we create (set (reg)
+			       (reg)) here.  */
+			    success
+			      = validate_change (next, &SET_SRC (set), reg, 0);
+			  else
+			    success = 0;
+			}
 		      else if ((rtx_cost (new_src, PLUS)
 				< COSTS_N_INSNS (1) + rtx_cost (src3, SET))
 			       && have_add2_insn (reg, new_src))