X-Git-Url: http://git.joshuawise.com/firearm.git/blobdiff_plain/960947a70a85ad40fe2569500806552d11f1e02d..b7359a807e88320755edab8987c269a0b9c83f26:/Decode.v diff --git a/Decode.v b/Decode.v index 5690062..22c6eae 100644 --- a/Decode.v +++ b/Decode.v @@ -2,169 +2,236 @@ 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 [3:0] regsel0, - output [3:0] regsel1, - output [3:0] regsel2, - input [31:0] iregs0, - input [31:0] iregs1, - input [31:0] iregs2 + output reg carry, + + 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] op0_out, op1_out, op2_out; + wire carry_out; /* shifter stuff */ wire [31:0] shift_oper; wire [31:0] shift_res; wire shift_cflag_out; + wire [31:0] rotate_res; - 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), - .operand(regs1), - .reg_amt(regs2), - .cflag_in(cps_in[`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 @ (*) begin - casez (ansn) - 32'b????000000??????????????1001????: begin /* Multiply */ + SuckLessRotator whirr(.oper({24'b0, insn[7:0]}), + .amt(insn[11:8]), + .res(rotate_res)); + + 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 and exchange */ + 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; - regsel0 = ansn[15:12]; /* Rn */ - regsel1 = ansn[3:0]; /* Rm */ - regsel2 = ansn[11:8]; /* Rs */ - op1_res = regs1; - new_cps = cps_in; - end -/* - 32'b????00001???????????????1001????: begin * Multiply long * - regsel0 = ansn[11:8]; * Rn * - regsel1 = ansn[3:0]; * Rm * - regsel2 = 4'b0; * anyus * - op1_res = regs1; - end -*/ + 32'b????00??????????????????????????: /* ALU */ + rpc = inpc - (insn[25] ? 8 : (insn[4] ? 12 : 8)); + default: /* X everything else out */ + rpc = 32'hxxxxxxxx; + endcase + + always @(*) begin + read_0 = 4'hx; + read_1 = 4'hx; + read_2 = 4'hx; + + casez (insn) + 32'b????000000??????????????1001????: /* Multiply -- must come before ALU, because it pattern matches a specific case of ALU */ + begin + read_0 = insn[15:12]; /* Rn */ + read_1 = insn[3:0]; /* Rm */ + read_2 = insn[11:8]; /* Rs */ + end +// 32'b????00001???????????????1001????, /* Multiply long */ +// 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) */ + 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) */ + read_0 = insn[3:0]; /* Rm */ + 32'b????00??????????????????????????: /* ALU */ + begin + read_0 = insn[19:16]; /* Rn */ + read_1 = insn[3:0]; /* Rm */ + read_2 = insn[11:8]; /* Rs for shift */ + end + 32'b????00010?00????????00001001????: /* Atomic swap */ + begin + read_0 = insn[19:16]; /* Rn */ + read_1 = insn[3:0]; /* Rm */ + end + 32'b????000100101111111111110001????: /* Branch and exchange */ + read_0 = insn[3:0]; /* Rn */ + 32'b????000??0??????????00001??1????: /* Halfword transfer - register offset */ + begin + read_0 = insn[19:16]; + read_1 = insn[3:0]; + end + 32'b????000??1??????????00001??1????: /* Halfword transfer - immediate offset */ + begin + read_0 = insn[19:16]; + end + 32'b????011????????????????????1????: /* Undefined. I hate ARM */ + begin end + 32'b????01??????????????????????????: /* Single data transfer */ + begin + read_0 = insn[19:16]; /* Rn */ + read_1 = insn[3:0]; /* Rm */ + end + 32'b????100?????????????????????????: /* Block data transfer */ + read_0 = insn[19:16]; + 32'b????101?????????????????????????: /* Branch */ + begin end + 32'b????110?????????????????????????: /* Coprocessor data transfer */ + read_0 = insn[19:16]; + 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: + $display("Undecoded instruction"); + endcase + end + + always @(*) begin + op0_out = 32'hxxxxxxxx; + op1_out = 32'hxxxxxxxx; + op2_out = 32'hxxxxxxxx; + carry_out = 1'bx; + casez (insn) + 32'b????000000??????????????1001????: begin /* Multiply */ + 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) */ - rpc = inpc - 8; - new_cps = cps_in; end 32'b????00010?101001111100000000????: begin /* MSR (Transfer register to PSR) */ - rpc = inpc - 8; - new_cps = cps_in; + op0_out = regs0; end - 32'b????00?10?1010001111????????????: begin /* MSR (Transfer register or immediate to PSR, flag bits onry) */ - rpc = inpc - 8; - new_cps = cps_in; + 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 = rotate_res; + end else begin + op0_out = regs0; + end 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})); + op0_out = regs0; + if(insn[25]) begin /* the constant case */ + carry_out = incpsr[`CPSR_C]; + op1_out = rotate_res; end else begin - new_cps = {cps_in[31:30], shift_cflag_out, cps_in[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 */ - rpc = inpc - 8; - regsel0 = ansn[19:16]; /* Rn */ - regsel1 = ansn[3:0]; /* Rm */ - regsel2 = 4'b0; /* anyus */ - op1_res = regs1; + op0_out = regs0; + op1_out = regs1; end 32'b????000100101111111111110001????: begin /* Branch and exchange */ - rpc = inpc - 8; - regsel0 = ansn[3:0]; /* Rn */ - new_cps = cps_in; + op0_out = regs0; 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; - op1_res = regs1; - new_cps = cps_in; + op0_out = regs0; + op1_out = regs1; 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; + 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 */ - 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; + op0_out = regs0; + if(insn[25]) begin + op1_out = {20'b0, insn[11:0]}; + carry_out = incpsr[`CPSR_C]; end else begin - op1_res = shift_res; - new_cps = {cps_in[31:30], shift_cflag_out, cps_in[28:0]}; + op1_out = shift_res; + carry_out = shift_cflag_out; 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; + op0_out = regs0; + op1_out = {16'b0, insn[15:0]}; end 32'b????101?????????????????????????: begin /* Branch */ - rpc = inpc - 8; - op1_res = {{6{ansn[23]}}, ansn[23:0], 2'b0}; - new_cps = cps_in; + op0_out = {{6{insn[23]}}, insn[23:0], 2'b0}; 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; + op0_out = regs0; + op1_out = {24'b0, insn[7:0]}; end 32'b????1110???????????????????0????: begin /* Coprocessor data op */ - rpc = inpc - 8; - new_cps = cps_in; end 32'b????1110???????????????????1????: begin /* Coprocessor register transfer */ - rpc = inpc - 8; - new_cps = cps_in; + op0_out = regs0; end 32'b????1111????????????????????????: begin /* SWI */ - rpc = inpc - 8; - new_cps = cps_in; end default: begin end endcase end always @ (posedge clk) begin - op0 <= regs0; /* Rn - always */ - op1 <= op1_res; /* 'operand 2' - Rm */ - op2 <= regs2; /* thirdedge - Rs */ - cps_out <= new_cps; + 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, @@ -173,41 +240,99 @@ module IHATEARMSHIFT( 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 */ - /* might want to write our own damn shifter that does arithmetic/logical efficiently and stuff */ - always @ (*) begin - 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 + SuckLessShifter biteme(.oper(operand), + .carryin(cflag_in), + .amt(shift_amt), + .is_arith(is_arith), + .is_rot(is_rot), + .res(rshift_res), + .carryout(rshift_cout)); - case (insn[6:5]) /* shift type */ + always @(*) + case (insn[6:5]) `SHIFT_LSL: begin - {cflag_out, res} = {cflag_in, operand} << {elanus & shift_amt[5], shift_amt[4:0]}; + /* 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: + {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 - end +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[16:1] : {16{pushbits}}, stage1[32:17], stage1[16]} : stage1; + assign stage3 = amt[3] ? {is_rot ? stage2[8:1] : {8{pushbits}}, stage2[32:9], stage2[8]} : stage2; + assign stage4 = amt[2] ? {is_rot ? stage3[4:1] : {4{pushbits}}, stage3[32:5], stage3[4]} : stage3; + assign stage5 = amt[1] ? {is_rot ? stage4[2:1] : {2{pushbits}}, stage4[32:3], stage4[2]} : stage4; + assign {res, carryout} = amt[0] ? {is_rot ? stage5[1] : pushbits, stage5[32:2], stage5[1]} : stage5; + +endmodule + +module SuckLessRotator( + input [31:0] oper, + input [3:0] amt, + output [31:0] res +); + + wire [31:0] stage1, stage2, stage3; + assign stage1 = amt[3] ? {oper[15:0], oper[31:16]} : oper; + assign stage2 = amt[2] ? {stage1[7:0], stage1[31:8]} : stage1; + assign stage3 = amt[1] ? {stage2[3:0], stage2[31:4]} : stage2; + assign res = amt[0] ? {stage3[1:0], stage3[31:2]} : stage3; + endmodule