module Decode(
input clk,
- input [31:0] ansn,
+ input [31:0] insn,
input [31:0] inpc,
- input [31:0] cps_in,
+ input [31:0] incpsr,
output reg [31:0] op0,
output reg [31:0] op1,
output reg [31:0] op2,
- output reg [31:0] cps_out,
+ output reg [31:0] outcpsr,
- output [3:0] regsel0,
- output [3:0] regsel1,
- output [3:0] regsel2,
- input [31:0] iregs0,
- input [31:0] iregs1,
- input [31:0] iregs2
+ output [3:0] read_0,
+ output [3:0] read_1,
+ output [3:0] read_2,
+ input [31:0] rdata_0,
+ input [31:0] rdata_1,
+ input [31:0] rdata_2
);
wire [31:0] regs0, regs1, regs2, rpc;
- wire [31:0] op1_res, new_cps;
+ wire [31:0] op1_res, cpsr;
/* shifter stuff */
wire [31:0] shift_oper;
wire [31:0] shift_res;
wire shift_cflag_out;
- assign regs0 = (regsel0 == 4'b1111) ? rpc : iregs0;
- assign regs1 = (regsel1 == 4'b1111) ? rpc : iregs1;
- assign regs2 = iregs2; /* use regs2 for things that cannot be r15 */
+ assign regs0 = (read_0 == 4'b1111) ? rpc : rdata_0;
+ assign regs1 = (read_1 == 4'b1111) ? rpc : rdata_1;
+ assign regs2 = rdata_2; /* use regs2 for things that cannot be r15 */
- IHATEARMSHIFT blowme(.insn(ansn),
+ IHATEARMSHIFT blowme(.insn(insn),
.operand(regs1),
.reg_amt(regs2),
- .cflag_in(cps_in[`CPSR_C]),
+ .cflag_in(incpsr[`CPSR_C]),
.res(shift_res),
.cflag_out(shift_cflag_out));
+
+ always @(*)
+ casez (insn)
+ 32'b????000000??????????????1001????, /* Multiply -- must come before ALU, because it pattern matches a specific case of ALU */
+// 32'b????00001???????????????1001????, /* Multiply long */
+ 32'b????00010?001111????000000000000, /* MRS (Transfer PSR to register) */
+ 32'b????00010?101001111100000000????, /* MSR (Transfer register to PSR) */
+ 32'b????00?10?1010001111????????????, /* MSR (Transfer register or immediate to PSR, flag bits only) */
+ 32'b????00010?00????????00001001????, /* Atomic swap */
+ 32'b????000100101111111111110001????, /* Branch */
+ 32'b????000??0??????????00001??1????, /* Halfword transfer - register offset */
+ 32'b????000??1??????????00001??1????, /* Halfword transfer - register offset */
+ 32'b????011????????????????????1????, /* Undefined. I hate ARM */
+ 32'b????01??????????????????????????, /* Single data transfer */
+ 32'b????100?????????????????????????, /* Block data transfer */
+ 32'b????101?????????????????????????, /* Branch */
+ 32'b????110?????????????????????????, /* Coprocessor data transfer */
+ 32'b????1110???????????????????0????, /* Coprocessor data op */
+ 32'b????1110???????????????????1????, /* Coprocessor register transfer */
+ 32'b????1111????????????????????????: /* SWI */
+ rpc = inpc - 8;
+ 32'b????00??????????????????????????: /* ALU */
+ rpc = inpc - (insn[25] ? 8 : (insn[4] ? 12 : 8));
+ default: /* X everything else out */
+ rpc = 32'hxxxxxxxx;
+ endcase
always @ (*) begin
- casez (ansn)
+ casez (insn)
32'b????000000??????????????1001????: begin /* Multiply */
- rpc = inpc - 8;
- regsel0 = ansn[15:12]; /* Rn */
- regsel1 = ansn[3:0]; /* Rm */
- regsel2 = ansn[11:8]; /* Rs */
+ read_0 = insn[15:12]; /* Rn */
+ read_1 = insn[3:0]; /* Rm */
+ read_2 = insn[11:8]; /* Rs */
op1_res = regs1;
- new_cps = cps_in;
+ cpsr = incpsr;
end
/*
32'b????00001???????????????1001????: begin * Multiply long *
- regsel0 = ansn[11:8]; * Rn *
- regsel1 = ansn[3:0]; * Rm *
- regsel2 = 4'b0; * anyus *
+ read_0 = insn[11:8]; * Rn *
+ read_1 = insn[3:0]; * Rm *
+ read_2 = 4'b0; * anyus *
op1_res = regs1;
end
*/
32'b????00010?001111????000000000000: begin /* MRS (Transfer PSR to register) */
- rpc = inpc - 8;
- new_cps = cps_in;
+ cpsr = incpsr;
end
32'b????00010?101001111100000000????: begin /* MSR (Transfer register to PSR) */
- rpc = inpc - 8;
- new_cps = cps_in;
+ cpsr = incpsr;
end
32'b????00?10?1010001111????????????: begin /* MSR (Transfer register or immediate to PSR, flag bits onry) */
- rpc = inpc - 8;
- new_cps = cps_in;
+ cpsr = incpsr;
end
32'b????00??????????????????????????: begin /* ALU */
- rpc = inpc - (ansn[25] ? 8 : (ansn[4] ? 12 : 8));
- regsel0 = ansn[19:16]; /* Rn */
- regsel1 = ansn[3:0]; /* Rm */
- regsel2 = ansn[11:8]; /* Rs for shift */
- if(ansn[25]) begin /* the constant case */
- 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}));
+ read_0 = insn[19:16]; /* Rn */
+ read_1 = insn[3:0]; /* Rm */
+ read_2 = insn[11:8]; /* Rs for shift */
+ if(insn[25]) begin /* the constant case */
+ cpsr = incpsr;
+ op1_res = ({24'b0, insn[7:0]} >> {insn[11:8], 1'b0}) | ({24'b0, insn[7:0]} << (5'b0 - {insn[11:8], 1'b0}));
end else begin
- new_cps = {cps_in[31:30], shift_cflag_out, cps_in[28:0]};
+ cpsr = {incpsr[31:30], shift_cflag_out, incpsr[28:0]};
op1_res = shift_res;
end
end
32'b????00010?00????????00001001????: begin /* Atomic swap */
- rpc = inpc - 8;
- regsel0 = ansn[19:16]; /* Rn */
- regsel1 = ansn[3:0]; /* Rm */
- regsel2 = 4'b0; /* anyus */
+ read_0 = insn[19:16]; /* Rn */
+ read_1 = insn[3:0]; /* Rm */
+ read_2 = 4'b0; /* anyus */
op1_res = regs1;
end
32'b????000100101111111111110001????: begin /* Branch and exchange */
- rpc = inpc - 8;
- regsel0 = ansn[3:0]; /* Rn */
- new_cps = cps_in;
+ read_0 = insn[3:0]; /* Rn */
+ cpsr = incpsr;
end
32'b????000??0??????????00001??1????: begin /* Halfword transfer - register offset */
- rpc = inpc - 8;
- regsel0 = ansn[19:16];
- regsel1 = ansn[3:0];
- regsel2 = 4'b0;
+ read_0 = insn[19:16];
+ read_1 = insn[3:0];
+ read_2 = 4'b0;
op1_res = regs1;
- new_cps = cps_in;
+ cpsr = incpsr;
end
32'b????000??1??????????00001??1????: begin /* Halfword transfer - immediate offset */
- rpc = inpc - 8;
- regsel0 = ansn[19:16];
- regsel1 = ansn[3:0];
- op1_res = {24'b0, ansn[11:8], ansn[3:0]};
- new_cps = cps_in;
+ read_0 = insn[19:16];
+ read_1 = insn[3:0];
+ op1_res = {24'b0, insn[11:8], insn[3:0]};
+ cpsr = incpsr;
end
32'b????011????????????????????1????: begin /* Undefined. I hate ARM */
/* eat shit */
end
32'b????01??????????????????????????: begin /* Single data transfer */
- rpc = inpc - 8;
- regsel0 = ansn[19:16]; /* Rn */
- regsel1 = ansn[3:0]; /* Rm */
- if(ansn[25]) begin
- op1_res = {20'b0, ansn[11:0]};
- new_cps = cps_in;
+ read_0 = insn[19:16]; /* Rn */
+ read_1 = insn[3:0]; /* Rm */
+ if(insn[25]) begin
+ op1_res = {20'b0, insn[11:0]};
+ cpsr = incpsr;
end else begin
op1_res = shift_res;
- new_cps = {cps_in[31:30], shift_cflag_out, cps_in[28:0]};
+ cpsr = {incpsr[31:30], shift_cflag_out, incpsr[28:0]};
end
end
32'b????100?????????????????????????: begin /* Block data transfer */
- rpc = inpc - 8;
- regsel0 = ansn[19:16];
- op1_res = {16'b0, ansn[15:0]};
- new_cps = cps_in;
+ read_0 = insn[19:16];
+ op1_res = {16'b0, insn[15:0]};
+ cpsr = incpsr;
end
32'b????101?????????????????????????: begin /* Branch */
- rpc = inpc - 8;
- op1_res = {{6{ansn[23]}}, ansn[23:0], 2'b0};
- new_cps = cps_in;
+ op1_res = {{6{insn[23]}}, insn[23:0], 2'b0};
+ cpsr = incpsr;
end
32'b????110?????????????????????????: begin /* Coprocessor data transfer */
- rpc = inpc - 8;
- regsel0 = ansn[19:16];
- op1_res = {24'b0, ansn[7:0]};
- new_cps = cps_in;
+ read_0 = insn[19:16];
+ op1_res = {24'b0, insn[7:0]};
+ cpsr = incpsr;
end
32'b????1110???????????????????0????: begin /* Coprocessor data op */
- rpc = inpc - 8;
- new_cps = cps_in;
+ cpsr = incpsr;
end
32'b????1110???????????????????1????: begin /* Coprocessor register transfer */
- rpc = inpc - 8;
- new_cps = cps_in;
+ cpsr = incpsr;
end
32'b????1111????????????????????????: begin /* SWI */
- rpc = inpc - 8;
- new_cps = cps_in;
+ cpsr = incpsr;
end
default: begin end
endcase
op0 <= regs0; /* Rn - always */
op1 <= op1_res; /* 'operand 2' - Rm */
op2 <= regs2; /* thirdedge - Rs */
- cps_out <= new_cps;
+ outcpsr <= cpsr;
end
endmodule
/* might want to write our own damn shifter that does arithmetic/logical efficiently and stuff */
- always @ (*) begin
+ always @(*)
if(insn[4]) begin
shift_amt = {|reg_amt[7:5], reg_amt[4:0]};
elanus = 1'b1;
shift_amt = {insn[11:7] == 5'b0, insn[11:7]};
elanus = 1'b0;
end
-
+
+ always @(*)
case (insn[6:5]) /* shift type */
`SHIFT_LSL: begin
{cflag_out, res} = {cflag_in, operand} << {elanus & shift_amt[5], shift_amt[4:0]};
end
end
endcase
- end
endmodule
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