reg prevstall = 0;
always @(posedge clk)
prevstall <= outstall;
-
+
always @(*)
begin
outstall = stall;
- next_outbubble = inbubble | flush | delayedflush;
+
+ casez (insn)
+ `DECODE_ALU_MULT: /* Multiply -- must come before ALU, because it pattern matches a specific case of ALU */
+ outstall = outstall | ((!prevstall | !mult_done) && !inbubble);
+ endcase
+ end
+
+ /* ALU inputs */
+ always @(*)
+ begin
+ alu_in0 = op0;
+ alu_in1 = op1;
+ alu_op = insn[24:21];
+ alu_setflags = insn[20] /* S */;
+ end
+
+ /* Register outputs */
+ always @(*)
+ begin
next_outcpsr = cpsr;
next_outspsr = spsr;
next_outcpsrup = 0;
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'h00000000;
-
- casez (insn)
+
+ casez(insn)
`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 = outstall | ((!prevstall | !mult_done) && !inbubble);
- next_outbubble = next_outbubble | !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_outcpsrup = insn[20] /* S */;
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) */
begin
next_write_reg = 1;
next_write_data = spsr;
else
next_write_data = cpsr;
- next_outcpsrup = 1;
end
`DECODE_ALU_MSR, /* MSR (Transfer register to PSR) */
`DECODE_ALU_MSR_FLAGS: /* MSR (Transfer register or immediate to PSR, flag bits only) */
begin end
`DECODE_ALU: /* ALU */
begin
- alu_in0 = op0;
- alu_in1 = op1;
- alu_op = insn[24:21];
- alu_setflags = insn[20] /* S */;
-
if (alu_setres) begin
next_write_reg = 1;
next_write_num = insn[15:12] /* Rd */;
next_write_data = alu_result;
end
- next_outcpsr = ((insn[15:12] == 4'b1111) && insn[20]) ? spsr : alu_outcpsr;
- next_outcpsrup = insn[20] /* S */;
+ if (insn[20] /* S */) begin
+ next_outcpsrup = 1;
+ next_outcpsr = ((insn[15:12] == 4'b1111) && insn[20]) ? spsr : alu_outcpsr;
+ 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[24] /* L */) begin
+ next_write_reg = 1;
+ next_write_num = 4'hE; /* link register */
+ next_write_data = pc + 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)
+ `DECODE_ALU_MULT:
+ begin
+ if (!prevstall /* i.e., this is a new one */ && !inbubble /* i.e., this is a real one */)
+ 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
+ end
+ endcase
+ end
+
+ /* Miscellaneous cleanup. */
+ always @(*)
+ begin
+ next_outbubble = inbubble | flush | delayedflush;
+
+ jmp = 1'b0;
+ jmppc = 32'h00000000;
+
+ casez (insn)
+ `DECODE_ALU_MULT: /* Multiply -- must come before ALU, because it pattern matches a specific case of ALU */
+ next_outbubble = next_outbubble | !mult_done | !prevstall;
+ `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(!inbubble && !flush && !delayedflush && !outstall /* Let someone else take precedence. */) 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 */
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
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
end
`ALU_CMP: begin
{flag_c, result} = diff;
+ flag_c = !flag_c;
flag_v = diff_v;
setres = 1'b0;
end
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