output reg [31:0] op0,
output reg [31:0] op1,
output reg [31:0] op2,
- output reg [31:0] outcpsr,
+ output reg carry,
output [3:0] read_0,
output [3:0] read_1,
);
wire [31:0] regs0, regs1, regs2, rpc;
- wire [31:0] op1_res, cpsr;
+ wire [31:0] op0_out, op1_out, op2_out;
+ wire carry_out;
/* shifter stuff */
wire [31:0] shift_oper;
assign regs1 = (read_1 == 4'b1111) ? rpc : rdata_1;
assign regs2 = rdata_2; /* use regs2 for things that cannot be r15 */
- IHATEARMSHIFT blowme(.insn(insn),
- .operand(regs1),
- .reg_amt(regs2),
- .cflag_in(incpsr[`CPSR_C]),
- .res(shift_res),
- .cflag_out(shift_cflag_out));
-
+ IREALLYHATEARMSHIFT blowme(.insn(insn),
+ .operand(regs1),
+ .reg_amt(regs2),
+ .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 */
// read_0 = insn[11:8]; /* Rn */
// read_1 = insn[3:0]; /* Rm */
// read_2 = 4'b0; /* anyus */
- 32'b????00010?001111????000000000000, /* MRS (Transfer PSR to register) */
+ 32'b????00010?001111????000000000000: /* MRS (Transfer PSR to register) */
+ begin end
32'b????00010?101001111100000000????, /* MSR (Transfer register to PSR) */
32'b????00?10?1010001111????????????: /* MSR (Transfer register or immediate to PSR, flag bits only) */
- begin end /* Everything stays x'ed out. */
+ read_0 = insn[3:0]; /* Rm */
32'b????00??????????????????????????: /* ALU */
begin
read_0 = insn[19:16]; /* Rn */
32'b????000??1??????????00001??1????: /* Halfword transfer - immediate offset */
begin
read_0 = insn[19:16];
- read_1 = insn[3:0];
end
32'b????011????????????????????1????: /* Undefined. I hate ARM */
begin end
begin end
32'b????110?????????????????????????: /* Coprocessor data transfer */
read_0 = insn[19:16];
- 32'b????1110???????????????????0????, /* Coprocessor data op */
- 32'b????1110???????????????????1????, /* Coprocessor register transfer */
+ 32'b????1110???????????????????0????: /* Coprocessor data op */
+ begin end
+ 32'b????1110???????????????????1????: /* Coprocessor register transfer */
+ read_0 = insn[15:12];
32'b????1111????????????????????????: /* SWI */
begin end
default:
end
always @(*) begin
- op1_res = 32'hxxxxxxxx;
- cpsr = 32'hxxxxxxxx;
+ op0_out = 32'hxxxxxxxx;
+ op1_out = 32'hxxxxxxxx;
+ op2_out = 32'hxxxxxxxx;
+ carry_out = 1'bx;
casez (insn)
32'b????000000??????????????1001????: begin /* Multiply */
- op1_res = regs1;
- cpsr = incpsr;
+ op0_out = regs0;
+ op1_out = regs1;
+ op2_out = regs2;
end
// 32'b????00001???????????????1001????: begin /* Multiply long */
// op1_res = regs1;
// end
32'b????00010?001111????000000000000: begin /* MRS (Transfer PSR to register) */
- cpsr = incpsr;
end
32'b????00010?101001111100000000????: begin /* MSR (Transfer register to PSR) */
- cpsr = incpsr;
+ op0_out = regs0;
end
- 32'b????00?10?1010001111????????????: begin /* MSR (Transfer register or immediate to PSR, flag bits onry) */
- cpsr = incpsr;
+ 32'b????00?10?1010001111????????????: begin /* MSR (Transfer register or immediate to PSR, flag bits only) */
+ if(insn[25]) begin /* the constant case */
+ op0_out = ({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
+ op0_out = regs0;
+ end
end
32'b????00??????????????????????????: begin /* ALU */
+ op0_out = regs0;
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}));
+ carry_out = incpsr[`CPSR_C];
+ op1_out = ({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
- cpsr = {incpsr[31:30], shift_cflag_out, incpsr[28:0]};
- op1_res = shift_res;
+ carry_out = shift_cflag_out;
+ op1_out = shift_res;
end
end
32'b????00010?00????????00001001????: begin /* Atomic swap */
- op1_res = regs1;
+ op0_out = regs0;
+ op1_out = regs1;
end
32'b????000100101111111111110001????: begin /* Branch and exchange */
- cpsr = incpsr;
+ op0_out = regs0;
end
32'b????000??0??????????00001??1????: begin /* Halfword transfer - register offset */
- op1_res = regs1;
- cpsr = incpsr;
+ op0_out = regs0;
+ op1_out = regs1;
end
32'b????000??1??????????00001??1????: begin /* Halfword transfer - immediate offset */
- op1_res = {24'b0, insn[11:8], insn[3:0]};
- cpsr = incpsr;
+ op0_out = regs0;
+ op1_out = {24'b0, insn[11:8], insn[3:0]};
end
32'b????011????????????????????1????: begin /* Undefined. I hate ARM */
/* eat shit */
end
32'b????01??????????????????????????: begin /* Single data transfer */
+ op0_out = regs0;
if(insn[25]) begin
- op1_res = {20'b0, insn[11:0]};
- cpsr = incpsr;
+ op1_out = {20'b0, insn[11:0]};
+ carry_out = incpsr[`CPSR_C];
end else begin
- op1_res = shift_res;
- cpsr = {incpsr[31:30], shift_cflag_out, incpsr[28:0]};
+ op1_out = shift_res;
+ carry_out = shift_cflag_out;
end
end
32'b????100?????????????????????????: begin /* Block data transfer */
- op1_res = {16'b0, insn[15:0]};
- cpsr = incpsr;
+ op0_out = regs0;
+ op1_out = {16'b0, insn[15:0]};
end
32'b????101?????????????????????????: begin /* Branch */
- op1_res = {{6{insn[23]}}, insn[23:0], 2'b0};
- cpsr = incpsr;
+ op0_out = {{6{insn[23]}}, insn[23:0], 2'b0};
end
32'b????110?????????????????????????: begin /* Coprocessor data transfer */
- op1_res = {24'b0, insn[7:0]};
- cpsr = incpsr;
+ op0_out = regs0;
+ op1_out = {24'b0, insn[7:0]};
end
32'b????1110???????????????????0????: begin /* Coprocessor data op */
- cpsr = incpsr;
end
32'b????1110???????????????????1????: begin /* Coprocessor register transfer */
- cpsr = incpsr;
+ op0_out = regs0;
end
32'b????1111????????????????????????: begin /* SWI */
- cpsr = incpsr;
end
default: begin end
endcase
end
always @ (posedge clk) begin
- op0 <= regs0; /* Rn - always */
- op1 <= op1_res; /* 'operand 2' - Rm */
- op2 <= regs2; /* thirdedge - Rs */
- outcpsr <= cpsr;
+ op0 <= op0_out; /* Rn - always */
+ op1 <= op1_out; /* 'operand 2' - Rm */
+ op2 <= op2_out; /* thirdedge - Rs */
+ carry <= carry_out;
end
endmodule
-module IHATEARMSHIFT(
+module IREALLYHATEARMSHIFT(
input [31:0] insn,
input [31:0] operand,
input [31:0] reg_amt,
output cflag_out
);
wire [5:0] shift_amt;
- wire elanus;
+ wire rshift_cout, is_arith, is_rot;
+ wire [31:0] rshift_res;
+ assign shift_amt = insn[4] ? {|reg_amt[7:5], reg_amt[4:0]} /* reg-specified shift */
+ : {insn[11:7] == 5'b0, insn[11:7]}; /* immediate shift */
+
+ SuckLessShifter biteme(.oper(operand),
+ .carryin(cflag_in),
+ .amt(shift_amt),
+ .is_arith(is_arith),
+ .is_rot(is_rot),
+ .res(rshift_res),
+ .carryout(rshift_cout));
- /* might want to write our own damn shifter that does arithmetic/logical efficiently and stuff */
always @(*)
- 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;
+ case (insn[6:5])
+ `SHIFT_LSL: begin
+ /* meaningless */
+ is_rot = 1'b0;
+ is_arith = 1'b0;
end
-
+ `SHIFT_LSR: begin
+ is_rot = 1'b0;
+ is_arith = 1'b0;
+ end
+ `SHIFT_ASR: begin
+ is_rot = 1'b0;
+ is_arith = 1'b1;
+ end
+ `SHIFT_ROR: begin
+ is_rot = 1'b1;
+ is_arith = 1'b0;
+ end
+ endcase
+
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
+ `SHIFT_LSL:
+ {cflag_out, res} = {cflag_in, operand} << {insn[4] & shift_amt[5], shift_amt[4:0]};
`SHIFT_LSR: begin
- {res, cflag_out} = {operand, cflag_in} >> shift_amt;
+ res = rshift_res;
+ cflag_out = rshift_cout;
end
`SHIFT_ASR: begin
- {res, cflag_out} = {operand, cflag_in} >> shift_amt | (operand[31] ? ~(33'h1FFFFFFFF >> shift_amt) : 33'b0);
+ res = rshift_res;
+ cflag_out = rshift_cout;
end
`SHIFT_ROR: begin
- if(!elanus && shift_amt[4:0] == 5'b0) begin /* RRX x.x */
+ if(!insn[4] && 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 == 6'b0) begin
- res = operand;
- cflag_out = cflag_in;
end else begin
- res = operand >> shift_amt[4:0] | operand << (5'b0 - shift_amt[4:0]);
- cflag_out = operand[shift_amt[4:0] - 5'b1];
+ res = rshift_res;
+ cflag_out = rshift_cout;
end
end
endcase
endmodule
+
+module SuckLessShifter(
+ input [31:0] oper,
+ input carryin,
+ input [5:0] amt,
+ input is_arith,
+ input is_rot,
+ output [31:0] res,
+ output carryout
+);
+
+ wire [32:0] stage1, stage2, stage3, stage4, stage5;
+
+ wire pushbits = is_arith & oper[31];
+
+ /* do a barrel shift */
+ assign stage1 = amt[5] ? {is_rot ? oper : {32{pushbits}}, oper[31]} : {oper, carryin};
+ assign stage2 = amt[4] ? {is_rot ? stage1[15:0] : {16{pushbits}}, stage1[31:16], stage1[15]} : stage1;
+ assign stage3 = amt[3] ? {is_rot ? stage2[7:0] : {8{pushbits}}, stage2[31:8], stage2[7]} : stage2;
+ assign stage4 = amt[2] ? {is_rot ? stage3[3:0] : {4{pushbits}}, stage3[31:4], stage3[3]} : stage3;
+ assign stage5 = amt[1] ? {is_rot ? stage4[1:0] : {2{pushbits}}, stage4[31:2], stage4[1]} : stage4;
+ assign {res, carryout} = amt[0] ? {is_rot ? stage5[0] : pushbits, stage5[31:1], stage5[0]} : stage5;
+
+endmodule
git.joshuawise.com / firearm.git / blobdiff