input [31:0] pc,
input [31:0] insn,
input [31:0] cpsr,
+ input [31:0] spsr,
input [31:0] op0,
input [31:0] op1,
input [31:0] op2,
output reg outstall = 0,
output reg outbubble = 1,
output reg [31:0] outcpsr = 0,
+ output reg [31:0] outspsr = 0,
output reg write_reg = 1'bx,
output reg [3:0] write_num = 4'bxxxx,
- output reg [31:0] write_data = 32'hxxxxxxxx
+ output reg [31:0] write_data = 32'hxxxxxxxx,
+ output reg [31:0] jmppc,
+ output reg jmp
);
reg mult_start;
wire alu_setres;
reg next_outbubble;
- reg [31:0] next_outcpsr;
+ reg [31:0] next_outcpsr, next_outspsr;
reg next_write_reg;
reg [3:0] next_write_num;
+
reg [31:0] next_write_data;
-
+
Multiplier multiplier(
.clk(clk), .Nrst(Nrst),
.start(mult_start), .acc0(mult_acc0), .in0(mult_in0),
begin
outbubble <= next_outbubble;
outcpsr <= next_outcpsr;
+ outspsr <= next_outspsr;
write_reg <= next_write_reg;
write_num <= next_write_num;
write_data <= next_write_data;
end
end
+ reg prevstall = 0;
+ always @(posedge clk)
+ prevstall <= outstall;
+
always @(*)
begin
outstall = stall;
- next_outbubble = inbubble;
+ next_outbubble = inbubble | flush;
next_outcpsr = cpsr;
+ next_outspsr = spsr;
next_write_reg = 0;
next_write_num = 4'hx;
next_write_data = 32'hxxxxxxxx;
-
+
+ mult_start = 0;
+ mult_acc0 = 32'hxxxxxxxx;
+ mult_in0 = 32'hxxxxxxxx;
+ mult_in1 = 32'hxxxxxxxx;
+
alu_in0 = 32'hxxxxxxxx;
alu_in1 = 32'hxxxxxxxx;
alu_op = 4'hx; /* hax! */
alu_setflags = 1'bx;
-
+
+ jmp = 1'b0;
+ jmppc = 32'hxxxxxxxx;
+
casez (insn)
- `DECODE_ALU_MULT, /* Multiply -- must come before ALU, because it pattern matches a specific case of ALU */
+ `DECODE_ALU_MULT: /* Multiply -- must come before ALU, because it pattern matches a specific case of ALU */
+ begin
+ if (!prevstall && !inbubble)
+ begin
+ mult_start = 1;
+ mult_acc0 = insn[21] /* A */ ? op0 /* Rn */ : 32'h0;
+ mult_in0 = op1 /* Rm */;
+ mult_in1 = op2 /* Rs */;
+ $display("New MUL instruction");
+ end
+ outstall = stall | ((!prevstall | !mult_done) && !inbubble);
+ next_outbubble = inbubble | !mult_done | !prevstall;
+ next_outcpsr = insn[20] /* S */ ? {mult_result[31] /* N */, mult_result == 0 /* Z */, 1'b0 /* C */, cpsr[28] /* V */, cpsr[27:0]} : cpsr;
+ next_write_reg = 1;
+ next_write_num = insn[19:16] /* Rd -- why the fuck isn't this the same place as ALU */;
+ next_write_data = mult_result;
+ end
// `DECODE_ALU_MUL_LONG, /* Multiply long */
- `DECODE_ALU_MRS, /* MRS (Transfer PSR to register) */
+ `DECODE_ALU_MRS: /* MRS (Transfer PSR to register) */
+ begin
+ next_write_reg = 1;
+ next_write_num = insn[15:12];
+ if (insn[22] /* Ps */)
+ next_write_data = spsr;
+ else
+ next_write_data = cpsr;
+ end
`DECODE_ALU_MSR, /* MSR (Transfer register to PSR) */
- `DECODE_ALU_MSR_FLAGS, /* MSR (Transfer register or immediate to PSR, flag bits only) */
+ `DECODE_ALU_MSR_FLAGS: /* MSR (Transfer register or immediate to PSR, flag bits only) */
+ if ((cpsr[4:0] == `MODE_USR) || (insn[16] /* that random bit */ == 1'b0)) /* flags only */
+ begin
+ if (insn[22] /* Ps */)
+ next_outspsr = {op0[31:29], spsr[28:0]};
+ else
+ next_outcpsr = {op0[31:29], cpsr[28:0]};
+ end else begin
+ if (insn[22] /* Ps */)
+ next_outspsr = op0;
+ else
+ next_outcpsr = op0;
+ end
`DECODE_ALU_SWP, /* Atomic swap */
`DECODE_ALU_BX, /* Branch */
`DECODE_ALU_HDATA_REG, /* Halfword transfer - register offset */
alu_in0 = op0;
alu_in1 = op1;
alu_op = insn[24:21];
- alu_setflags = insn[20] /* I */;
+ alu_setflags = insn[20] /* S */;
if (alu_setres) begin
next_write_reg = 1;
next_write_data = alu_result;
end
- next_outcpsr = alu_outcpsr;
+ next_outcpsr = ((insn[15:12] == 4'b1111) && insn[20]) ? spsr : alu_outcpsr;
end
`DECODE_LDRSTR_UNDEFINED, /* Undefined. I hate ARM */
`DECODE_LDRSTR, /* Single data transfer */
- `DECODE_LDMSTM, /* Block data transfer */
- `DECODE_BRANCH, /* Branch */
+ `DECODE_LDMSTM: /* Block data transfer */
+ begin end
+ `DECODE_BRANCH:
+ begin
+ if(!inbubble) begin
+ jmppc = pc + op0 + 32'h8;
+ if(insn[24]) begin
+ next_write_reg = 1;
+ next_write_num = 4'hE; /* link register */
+ next_write_data = pc - 32'h4;
+ end
+ jmp = 1'b1;
+ end
+ end /* Branch */
`DECODE_LDCSTC, /* Coprocessor data transfer */
`DECODE_CDP, /* Coprocessor data op */
`DECODE_MRCMCR, /* Coprocessor register transfer */
end
endmodule
-/* XXX is the interface correct? */
module ALU(
input clk,
input Nrst, /* XXX not used yet */
output reg [31:0] cpsr_out,
output reg setres
);
- wire [31:0] res;
- wire flag_n, flag_z, flag_c, flag_v, 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]);
- /* TODO XXX flag_v not set correctly */
always @(*) begin
res = 32'hxxxxxxxx;
setres = 1'bx;
end
`ALU_SUB: begin
{flag_c, result} = diff;
+ flag_v = diff_v;
setres = 1'b1;
end
`ALU_RSB: begin
{flag_c, result} = rdiff;
+ 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_v = diff_v | (diff[31] & ~result[31]);
setres = 1'b1;
end
`ALU_RSC: begin
{flag_c, result} = rdiff - {32'b0, (~cpsr[`CPSR_C])};
+ flag_v = rdiff_v | (rdiff[31] & ~result[31]);
setres = 1'b1;
end
`ALU_TST: begin
end
`ALU_CMP: begin
{flag_c, result} = diff;
+ 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
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