rtl: simplify urv_decode and urv_exec

4a459e87 · Tristan Gingold · 98e08ba0 · 4a459e87 · 4a459e87
Commit 4a459e87 authored Sep 13, 2022 by Tristan Gingold
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Showing with 11 additions and 17 deletions

urv_decode.v rtl/urv_decode.v +2 -2

urv_exec.v rtl/urv_exec.v +9 -15

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--- a/rtl/urv_decode.v
+++ b/rtl/urv_decode.v
@@ -314,9 +314,9 @@ module urv_decode

 	  case (d_opcode)
 	    `OPC_OP:
-	      x_is_add_o <= ~f_ir_i[30] && !(d_fun == `FUNC_SLT || d_fun == `FUNC_SLTU);
+	      x_is_add_o <= ~f_ir_i[30];
 	    `OPC_OP_IMM:
-	      x_is_add_o <= !(d_fun == `FUNC_SLT || d_fun == `FUNC_SLTU);
+	      x_is_add_o <= 1;
 	    `OPC_BRANCH:
 	      x_is_add_o <= 0;
 	    default:

--- a/rtl/urv_exec.v
+++ b/rtl/urv_exec.v
@@ -263,26 +263,20 @@ module urv_exec
   wire [32:0] alu_addsub_op1 = {d_is_signed_alu_op_i ? alu_op1[31] : 1'b0, alu_op1 };
   wire [32:0] alu_addsub_op2 = {d_is_signed_alu_op_i ? alu_op2[31] : 1'b0, alu_op2 };

-   reg [32:0]  alu_addsub_result;
-
   // ALU adder/subtractor
-   always@*
-     if(d_is_add_i)
-       alu_addsub_result <= alu_addsub_op1 + alu_addsub_op2;
-     else
-       alu_addsub_result <= alu_addsub_op1 - alu_addsub_op2;
-
+   wire [32:0]  alu_add = alu_addsub_op1 + alu_addsub_op2;
+   wire [32:0] 	alu_sub = alu_addsub_op1 - alu_addsub_op2;

   // the rest of the ALU
   always@*
     case (d_fun_i)
-       `FUNC_ADD:  alu_result <= alu_addsub_result[31:0];
-       `FUNC_XOR:  alu_result <= alu_op1 ^ alu_op2;
-       `FUNC_OR:   alu_result <= alu_op1 | alu_op2;
-       `FUNC_AND:  alu_result <= alu_op1 & alu_op2;
-       `FUNC_SLT:  alu_result <= alu_addsub_result[32]?1:0;
-       `FUNC_SLTU: alu_result <= alu_addsub_result[32]?1:0;
-       default:    alu_result <= 32'hx;
+       `FUNC_ADD:    alu_result <= d_is_add_i ? alu_add[31:0] : alu_sub[31:0];
+       `FUNC_XOR:    alu_result <= alu_op1 ^ alu_op2;
+       `FUNC_OR:     alu_result <= alu_op1 | alu_op2;
+       `FUNC_AND:    alu_result <= alu_op1 & alu_op2;
+       `FUNC_SLT,
+	 `FUNC_SLTU: alu_result <= {31'b0, alu_sub[32]};
+       default:      alu_result <= 32'hx;
     endcase // case (d_fun_i)

   // barel shifter