c4x.c (c4x_address_cost): Return cost of 1 for REG+REG addressing if strength reduction enabled.

	* config/c4x/c4x.c (c4x_address_cost): Return cost of 1 for
	REG+REG addressing if strength reduction enabled.

From-SVN: r25086

gcc/ChangeLog

+Tue Feb  9 10:46:42 1999  Michael Hayes  <m.hayes@elec.canterbury.ac.nz>
+
+	* config/c4x/c4x.c (c4x_address_cost): Return cost of 1 for
+	REG+REG addressing if strength reduction enabled.
+
 Tue Feb  9 10:10:31 1999  Michael Hayes  <m.hayes@elec.canterbury.ac.nz>
 
 	* config/c4x/t-c4x  (LIBGCC2_CFLAGS): Delete.

gcc/config/c4x/c4x.c

@@ -1508,6 +1508,14 @@ rtx addr;
 	    break;
 
 	  case REG:
+	    /* Paradoxically, if we want autoincrement addressing for
+	       complex arithmetic and structure arrays, we must give
+	       REG+REG addressing the same cost as REG addressing to
+	       prevent CSE from avoiding REG+REG addresses.  This is
+	       because GIV combination in loop.c is suboptimal and
+	       needs fixing.  */
+	    if (flag_strength_reduce)
+	      return 1;
 	    return 2;
 
 	  case CONST_INT: