RISC-V: Increase mult/div cost if not implemented in hardware.

	2018-01-15  Andrew Waterman  <andrew@sifive.com>
	gcc/
	* config/riscv/riscv.c (riscv_rtx_costs) <MULT>: Increase cost if
	!TARGET_MUL.
	<UDIV>: Increase cost if !TARGET_DIV.

From-SVN: r256722

gcc/ChangeLog

+2018-01-15  Andrew Waterman  <andrew@sifive.com>
+
+	* config/riscv/riscv.c (riscv_rtx_costs) <MULT>: Increase cost if
+	!TARGET_MUL.
+	<UDIV>: Increase cost if !TARGET_DIV.
+
 2018-01-15  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	* config/rs6000/rs6000.md (define_attr "type"): Remove delayed_cr.

gcc/config/riscv/riscv.c

@@ -1615,6 +1615,9 @@ riscv_rtx_costs (rtx x, machine_mode mode, int outer_code, int opno ATTRIBUTE_UN
     case MULT:
       if (float_mode_p)
 	*total = tune_info->fp_mul[mode == DFmode];
+      else if (!TARGET_MUL)
+	/* Estimate the cost of a library call.  */
+	*total = COSTS_N_INSNS (speed ? 32 : 6);
       else if (GET_MODE_SIZE (mode) > UNITS_PER_WORD)
 	*total = 3 * tune_info->int_mul[0] + COSTS_N_INSNS (2);
       else if (!speed)
@@ -1635,7 +1638,10 @@ riscv_rtx_costs (rtx x, machine_mode mode, int outer_code, int opno ATTRIBUTE_UN
 
     case UDIV:
     case UMOD:
-      if (speed)
+      if (!TARGET_DIV)
+	/* Estimate the cost of a library call.  */
+	*total = COSTS_N_INSNS (speed ? 32 : 6);
+      else if (speed)
 	*total = tune_info->int_div[mode == DImode];
       else
 	*total = COSTS_N_INSNS (1);