arc64: Increase div costs, encourage syntetic ones.

Author: Claudiu Zissulescu

gcc/config/arc64/arc64.c

@@ -3495,9 +3495,12 @@ arc64_rtx_costs (rtx x, machine_mode mode, rtx_code outer,
     case ASHIFT:
     case ASHIFTRT:
     case LSHIFTRT:
+    case MULT:
+      return true;
+
     case DIV:
     case UDIV:
-    case MULT:
+      *cost = COSTS_N_INSNS (12);
       return true;
 
     default:

gcc/config/arc64/arith.md

@@ -862,7 +862,7 @@
    (set_attr "length" "4")])
 
 
-;; 32 x 32 -> 64 (signed/unsigned)
+;; 32 x 32 -> 64 (signed/unsigned) Triggers FAIL: c-c++-common/torture/builtin-arith-overflow-12.c
 ;worse results;(define_expand "<ANY_EXTEND:su_optab>mulsidi3"
 ;worse results;  [(parallel [(set (match_operand:DI 0 "register_operand")
 ;worse results;		   (mult:DI
@@ -901,6 +901,7 @@
 ;worse results;  [(set_attr "length" "4,4,8")
 ;worse results;   (set_attr "type" "mpy")])
 
+
 ;; 16bit operations using SIMD instructions
 (define_insn "<optab>hi3"
   [(set (match_operand:HI 0 "register_operand"       "=r,    r,r")