X-Git-Url: http://git.joshuawise.com/firearm.git/blobdiff_plain/326fd4c33d4331252af93af8ee3fe5dbb7ff0d3f..3a57f3e5cbccf519c546eebed9fa9db7c328d72c:/Decode.v?ds=inline diff --git a/Decode.v b/Decode.v index fd8554b..44a948c 100644 --- a/Decode.v +++ b/Decode.v @@ -8,7 +8,7 @@ module Decode( 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, @@ -19,7 +19,8 @@ module Decode( ); 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; @@ -30,13 +31,13 @@ module Decode( 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 */ @@ -79,10 +80,11 @@ module Decode( // 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 */ @@ -104,7 +106,6 @@ module Decode( 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 @@ -119,8 +120,10 @@ module Decode( 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: @@ -129,95 +132,101 @@ module Decode( 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, @@ -226,41 +235,85 @@ 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 */ + + 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