some stuff
authorChristopher Lu <lu@stop.hsd1.pa.comcast.net>
Fri, 26 Dec 2008 12:30:44 +0000 (07:30 -0500)
committerChristopher Lu <lu@stop.hsd1.pa.comcast.net>
Fri, 26 Dec 2008 12:30:44 +0000 (07:30 -0500)
ARM_Constants.v
Decode.v

index a635c5e..2eedd3a 100644 (file)
@@ -45,3 +45,8 @@
 `define CPSR_V 28
 `define CPSR_I 7
 `define CPSR_F 6
+
+`define SHIFT_LSL 2'b00
+`define SHIFT_LSR 2'b01
+`define SHIFT_ASR 2'b10
+`define SHIFT_ROR 2'b11
index 85aefbf..5690062 100644 (file)
--- a/Decode.v
+++ b/Decode.v
@@ -1,3 +1,5 @@
+`include "ARM_Constants.v"
+
 module Decode(
        input clk,
        input [31:0] ansn,
@@ -28,12 +30,12 @@ module Decode(
        assign regs1 = (regsel1 == 4'b1111) ? rpc : iregs1;
        assign regs2 = iregs2; /* use regs2 for things that cannot be r15 */
 
-       IHATEARMSHIFT(.insn(ansn),
-                     .operand(regs1),
-                     .reg_amt(regs2),
-                     .cflag_in(cps_in[`COND_CBIT]),
-                     .res(shift_res),
-                     .cflag_out(shift_cflag));
+       IHATEARMSHIFT blowme(.insn(ansn),
+                            .operand(regs1),
+                            .reg_amt(regs2),
+                            .cflag_in(cps_in[`CPSR_C]),
+                            .res(shift_res),
+                            .cflag_out(shift_cflag_out));
 
        always @ (*) begin
                casez (ansn)
@@ -74,7 +76,7 @@ module Decode(
                                new_cps = cps_in;
                                op1_res = ({24'b0, ansn[7:0]} >> {ansn[11:8], 1'b0}) | ({24'b0, ansn[7:0]} << (5'b0 - {ansn[11:8], 1'b0}));
                        end else begin
-                               new_cps = {shift_cflag_out, cps_in[30:0]};
+                               new_cps = {cps_in[31:30], shift_cflag_out, cps_in[28:0]};
                                op1_res = shift_res;
                        end
                end
@@ -117,7 +119,7 @@ module Decode(
                                new_cps = cps_in;
                        end else begin
                                op1_res = shift_res;
-                               new_cps = shift_cflag_out;
+                               new_cps = {cps_in[31:30], shift_cflag_out, cps_in[28:0]};
                        end
                end
                32'b????100?????????????????????????: begin /* Block data transfer */
@@ -128,7 +130,7 @@ module Decode(
                end
                32'b????101?????????????????????????: begin /* Branch */
                        rpc = inpc - 8;
-                       op1_res = {6{ansn[23]}, ansn[23:0], 2'b0};
+                       op1_res = {{6{ansn[23]}}, ansn[23:0], 2'b0};
                        new_cps = cps_in;
                end
                32'b????110?????????????????????????: begin /* Coprocessor data transfer */
@@ -149,7 +151,7 @@ module Decode(
                        rpc = inpc - 8;
                        new_cps = cps_in;
                end
-               default:
+               default: begin end
                endcase
        end
 
@@ -170,22 +172,21 @@ module IHATEARMSHIFT(
        output [31:0] res,
        output cflag_out
 );
-       wire [1:0] shift_type;
        wire [5:0] shift_amt;
        wire elanus;
 
-       shift_type = insn[6:5];
-       if(insn[4]) begin
-               shift_amt = {|reg_amt[7:5], reg_amt[4:0]};
-               elanus = 1'b1;
-       end else begin
-               shift_amt = {insn[11:7] == 5'b0, insn[11:7]};
-               elanus = 1'b0;
-       end
 
        /* might want to write our own damn shifter that does arithmetic/logical efficiently and stuff */
        always @ (*) begin
-               case (shift_type)
+               if(insn[4]) begin
+                       shift_amt = {|reg_amt[7:5], reg_amt[4:0]};
+                       elanus = 1'b1;
+               end else begin
+                       shift_amt = {insn[11:7] == 5'b0, insn[11:7]};
+                       elanus = 1'b0;
+               end
+
+               case (insn[6:5]) /* shift type */
                `SHIFT_LSL: begin
                        {cflag_out, res} = {cflag_in, operand} << {elanus & shift_amt[5], shift_amt[4:0]};
                end
@@ -199,7 +200,7 @@ module IHATEARMSHIFT(
                        if(!elanus && shift_amt[4:0] == 5'b0) begin /* RRX x.x */
                                res = {cflag_in, operand[31:1]};
                                cflag_out = operand[0];
-                       end else if(!shift_amt) begin
+                       end else if(shift_amt == 6'b0) begin
                                res = operand;
                                cflag_out = cflag_in;
                        end else begin
@@ -207,5 +208,6 @@ module IHATEARMSHIFT(
                                cflag_out = operand[shift_amt[4:0] - 5'b1];
                        end
                end
+               endcase
        end
 endmodule
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