X-Git-Url: http://git.joshuawise.com/firearm.git/blobdiff_plain/4caf81e0cb02f814642cd7dc1a1d5ac05415415e..8c1ba49460599b87da679552ba8191ea184f0d15:/Execute.v diff --git a/Execute.v b/Execute.v index e00e93d..71f12e9 100644 --- a/Execute.v +++ b/Execute.v @@ -2,22 +2,253 @@ module Execute( input clk, input Nrst, /* XXX not used yet */ - input stall, + input stall_2a, input flush, - input inbubble, - input [31:0] pc, - input [31:0] insn, - input [31:0] cpsr, - input [31:0] op0, - input [31:0] op1, - input [31:0] op2, - input carry, + input bubble_2a, + input [31:0] pc_2a, + input [31:0] insn_2a, + input [31:0] cpsr_2a, + input [31:0] spsr_2a, + input [31:0] op0_2a, + input [31:0] op1_2a, + input [31:0] op2_2a, + input carry_2a, - output reg outstall = 0, - output reg outbubble = 1 + output reg outstall_2a = 0, + output reg bubble_3a = 1, + output reg [31:0] outcpsr = 0, + output reg [31:0] outspsr = 0, + output reg outcpsrup = 0, + output reg write_reg_3a = 1'bx, + output reg [3:0] write_num_3a = 4'bxxxx, + output reg [31:0] write_data_3a = 32'hxxxxxxxx, + output reg [31:0] jmppc_2a, + output reg jmp_2a, + output reg [31:0] pc_3a, + output reg [31:0] insn_3a, + output reg [31:0] op0_3a, op1_3a, op2_3a ); + reg mult_start; + reg [31:0] mult_acc0, mult_in0, mult_in1; + wire mult_done; + wire [31:0] mult_result; + + reg [31:0] alu_in0_2a, alu_in1_2a; + reg [3:0] alu_op_2a; + reg alu_setflags_2a; + wire [31:0] alu_result_2a, alu_outcpsr_2a; + wire alu_setres_2a; + + reg next_bubble_3a; + reg [31:0] next_outcpsr, next_outspsr; + reg next_outcpsrup; + + reg next_write_reg_3a; + reg [3:0] next_write_num_3a; + reg [31:0] next_write_data_3a; + + Multiplier multiplier( + .clk(clk), .Nrst(Nrst), + .start(mult_start), .acc0(mult_acc0), .in0(mult_in0), + .in1(mult_in1), .done(mult_done), .result(mult_result)); + + ALU alu( + .clk(clk), .Nrst(Nrst), + .in0(alu_in0_2a), .in1(alu_in1_2a), .cpsr(cpsr_2a), .op(alu_op_2a), + .setflags(alu_setflags_2a), .shifter_carry(carry_2a), + .result(alu_result_2a), .cpsr_out(alu_outcpsr_2a), .setres(alu_setres_2a)); + + always @(posedge clk) + begin + if (!stall_2a) + begin + bubble_3a <= next_bubble_3a; + outcpsr <= next_outcpsr; + outspsr <= next_outspsr; + outcpsrup <= next_outcpsrup; + write_reg_3a <= next_write_reg_3a; + write_num_3a <= next_write_num_3a; + write_data_3a <= next_write_data_3a; + pc_3a <= pc_2a; + insn_3a <= insn_2a; + op0_3a <= op0_2a; + op1_3a <= op1_2a; + op2_3a <= op2_2a; + end + end + + reg delayedflush = 0; + always @(posedge clk) + if (flush && outstall_2a /* halp! I can't do it now, maybe later? */) + delayedflush <= 1; + else if (!outstall_2a /* anything has been handled this time around */) + delayedflush <= 0; + + reg outstall_3a = 0; + always @(posedge clk) + outstall_3a <= outstall_2a; + + always @(*) + begin + outstall_2a = stall_2a; + + casez (insn_2a) + `DECODE_ALU_MULT: /* Multiply -- must come before ALU, because it pattern matches a specific case of ALU */ + outstall_2a = outstall_2a | ((!outstall_3a | !mult_done) && !bubble_2a); + endcase + end + + /* ALU inputs */ + always @(*) + begin + alu_in0_2a = op0_2a; + alu_in1_2a = op1_2a; + alu_op_2a = insn_2a[24:21]; + alu_setflags_2a = insn_2a[20] /* S */; + end + + /* Register outputs */ + always @(*) + begin + next_outcpsr = cpsr_2a; + next_outspsr = spsr_2a; + next_outcpsrup = 0; + next_write_reg_3a = 0; + next_write_num_3a = 4'hx; + next_write_data_3a = 32'hxxxxxxxx; + + casez(insn_2a) + `DECODE_ALU_MULT: /* Multiply -- must come before ALU, because it pattern matches a specific case of ALU */ + begin + next_outcpsr = insn_2a[20] /* S */ ? {mult_result[31] /* N */, mult_result == 0 /* Z */, 1'b0 /* C */, cpsr_2a[28] /* V */, cpsr_2a[27:0]} : cpsr_2a; + next_outcpsrup = insn_2a[20] /* S */; + next_write_reg_3a = 1; + next_write_num_3a = insn_2a[19:16] /* Rd -- why the fuck isn't this the same place as ALU */; + next_write_data_3a = mult_result; + end + `DECODE_ALU_MRS: /* MRS (Transfer PSR to register) */ + begin + next_write_reg_3a = 1; + next_write_num_3a = insn_2a[15:12]; + if (insn_2a[22] /* Ps */) + next_write_data_3a = spsr_2a; + else + next_write_data_3a = cpsr_2a; + end + `DECODE_ALU_MSR, /* MSR (Transfer register to PSR) */ + `DECODE_ALU_MSR_FLAGS: /* MSR (Transfer register or immediate to PSR, flag bits only) */ + begin + if ((cpsr_2a[4:0] == `MODE_USR) || (insn_2a[16] /* that random bit */ == 1'b0)) /* flags only */ + begin + if (insn_2a[22] /* Ps */) + next_outspsr = {op0_2a[31:29], spsr_2a[28:0]}; + else + next_outcpsr = {op0_2a[31:29], cpsr_2a[28:0]}; + end else begin + if (insn_2a[22] /* Ps */) + next_outspsr = op0_2a; + else + next_outcpsr = op0_2a; + end + next_outcpsrup = 1; + end + `DECODE_ALU_SWP, /* Atomic swap */ + `DECODE_ALU_BX, /* Branch */ + `DECODE_ALU_HDATA_REG, /* Halfword transfer - register offset */ + `DECODE_ALU_HDATA_IMM: /* Halfword transfer - immediate offset */ + begin end + `DECODE_ALU: /* ALU */ + begin + if (alu_setres_2a) begin + next_write_reg_3a = 1; + next_write_num_3a = insn_2a[15:12] /* Rd */; + next_write_data_3a = alu_result_2a; + end + + if (insn_2a[20] /* S */) begin + next_outcpsrup = 1; + next_outcpsr = ((insn_2a[15:12] == 4'b1111) && insn_2a[20]) ? spsr_2a : alu_outcpsr_2a; + end + end + `DECODE_LDRSTR_UNDEFINED, /* Undefined. I hate ARM */ + `DECODE_LDRSTR, /* Single data transfer */ + `DECODE_LDMSTM: /* Block data transfer */ + begin end + `DECODE_BRANCH: /* Branch */ + begin + if(insn_2a[24] /* L */) begin + next_write_reg_3a = 1; + next_write_num_3a = 4'hE; /* link register */ + next_write_data_3a = pc_2a + 32'h4; + end + end + endcase + end + + /* Multiplier inputs */ + always @(*) + begin + mult_start = 0; + mult_acc0 = 32'hxxxxxxxx; + mult_in0 = 32'hxxxxxxxx; + mult_in1 = 32'hxxxxxxxx; + + casez(insn_2a) + `DECODE_ALU_MULT: + begin + if (!outstall_3a /* i.e., this is a new one */ && !bubble_2a /* i.e., this is a real one */) + begin + mult_start = 1; + mult_acc0 = insn_2a[21] /* A */ ? op0_2a /* Rn */ : 32'h0; + mult_in0 = op1_2a /* Rm */; + mult_in1 = op2_2a /* Rs */; + $display("New MUL instruction"); + end + end + endcase + end + + /* Miscellaneous cleanup. */ + always @(*) + begin + next_bubble_3a = bubble_2a | flush | delayedflush; + + jmp_2a = 1'b0; + jmppc_2a = 32'h00000000; + + casez (insn_2a) + `DECODE_ALU_MULT: /* Multiply -- must come before ALU, because it pattern matches a specific case of ALU */ + next_bubble_3a = next_bubble_3a | !mult_done | !outstall_3a; + `DECODE_ALU_MRS, /* MRS (Transfer PSR to register) */ + `DECODE_ALU_MSR, /* MSR (Transfer register to PSR) */ + `DECODE_ALU_MSR_FLAGS, /* MSR (Transfer register or immediate to PSR, flag bits only) */ + `DECODE_ALU_SWP, /* Atomic swap */ + `DECODE_ALU_BX, /* Branch */ + `DECODE_ALU_HDATA_REG, /* Halfword transfer - register offset */ + `DECODE_ALU_HDATA_IMM, /* Halfword transfer - immediate offset */ + `DECODE_ALU, /* ALU */ + `DECODE_LDRSTR_UNDEFINED, /* Undefined. I hate ARM */ + `DECODE_LDRSTR, /* Single data transfer */ + `DECODE_LDMSTM: /* Block data transfer */ + begin end + `DECODE_BRANCH: + begin + if(!bubble_2a && !flush && !delayedflush && !outstall_2a /* Let someone else take precedence. */) begin + jmppc_2a = pc_2a + op0_2a + 32'h8; + jmp_2a = 1'b1; + end + end /* Branch */ + `DECODE_LDCSTC, /* Coprocessor data transfer */ + `DECODE_CDP, /* Coprocessor data op */ + `DECODE_MRCMCR, /* Coprocessor register transfer */ + `DECODE_SWI: /* SWI */ + begin end + default: /* X everything else out */ + begin end + endcase + end endmodule module Multiplier( @@ -56,3 +287,130 @@ module Multiplier( end end endmodule + +module ALU( + input clk, + input Nrst, /* XXX not used yet */ + + input [31:0] in0, + input [31:0] in1, + input [31:0] cpsr, + input [3:0] op, + input setflags, + input shifter_carry, + + output reg [31:0] result, + output reg [31:0] cpsr_out, + output reg setres +); + reg [31:0] res; + reg flag_n, flag_z, flag_c, flag_v; + wire [32:0] sum, diff, rdiff; + wire sum_v, diff_v, rdiff_v; + + assign sum = {1'b0, in0} + {1'b0, in1}; + assign diff = {1'b0, in0} - {1'b0, in1}; + assign rdiff = {1'b0, in1} - {1'b0, in0}; + assign sum_v = (in0[31] ^~ in1[31]) & (sum[31] ^ in0[31]); + assign diff_v = (in0[31] ^ in1[31]) & (diff[31] ^ in0[31]); + assign rdiff_v = (in0[31] ^ in1[31]) & (rdiff[31] ^ in1[31]); + + always @(*) begin + res = 32'hxxxxxxxx; + setres = 1'bx; + flag_c = cpsr[`CPSR_C]; + flag_v = cpsr[`CPSR_V]; + case(op) + `ALU_AND: begin + result = in0 & in1; + flag_c = shifter_carry; + setres = 1'b1; + end + `ALU_EOR: begin + result = in0 ^ in1; + flag_c = shifter_carry; + setres = 1'b1; + end + `ALU_SUB: begin + {flag_c, result} = diff; + flag_c = !flag_c; + flag_v = diff_v; + setres = 1'b1; + end + `ALU_RSB: begin + {flag_c, result} = rdiff; + flag_c = !flag_c; + flag_v = rdiff_v; + setres = 1'b1; + end + `ALU_ADD: begin + {flag_c, result} = sum; + flag_v = sum_v; + setres = 1'b1; + end + `ALU_ADC: begin + {flag_c, result} = sum + {32'b0, cpsr[`CPSR_C]}; + flag_v = sum_v | (~sum[31] & result[31]); + setres = 1'b1; + end + `ALU_SBC: begin + {flag_c, result} = diff - {32'b0, (~cpsr[`CPSR_C])}; + flag_c = !flag_c; + flag_v = diff_v | (diff[31] & ~result[31]); + setres = 1'b1; + end + `ALU_RSC: begin + {flag_c, result} = rdiff - {32'b0, (~cpsr[`CPSR_C])}; + flag_c = !flag_c; + flag_v = rdiff_v | (rdiff[31] & ~result[31]); + setres = 1'b1; + end + `ALU_TST: begin + result = in0 & in1; + flag_c = shifter_carry; + setres = 1'b0; + end + `ALU_TEQ: begin + result = in0 ^ in1; + flag_c = shifter_carry; + setres = 1'b0; + end + `ALU_CMP: begin + {flag_c, result} = diff; + flag_c = !flag_c; + flag_v = diff_v; + setres = 1'b0; + end + `ALU_CMN: begin + {flag_c, result} = sum; + flag_v = sum_v; + setres = 1'b0; + end + `ALU_ORR: begin + result = in0 | in1; + flag_c = shifter_carry; + setres = 1'b1; + end + `ALU_MOV: begin + result = in1; + flag_c = shifter_carry; + setres = 1'b1; + end + `ALU_BIC: begin + result = in0 & (~in1); + flag_c = shifter_carry; + setres = 1'b1; + end + `ALU_MVN: begin + result = ~in1; + flag_c = shifter_carry; + setres = 1'b1; + end + endcase + + flag_z = (result == 0); + flag_n = result[31]; + + cpsr_out = setflags ? {flag_n, flag_z, flag_c, flag_v, cpsr[27:0]} : cpsr; + end +endmodule