module Issue(
input clk,
- input Nrst,
+ input Nrst, /* XXX not used yet */
input stall, /* pipeline control */
- input flush,
+ input flush, /* XXX not used yet */
input inbubble, /* stage inputs */
input [31:0] insn,
input [31:0] inpc,
input [31:0] cpsr,
- output reg outstall, /* stage outputs */
- output reg outbubble,
- output reg [31:0] outpc,
- output reg [31:0] outinsn
+ output reg outstall = 0, /* stage outputs */
+ output reg outbubble = 1,
+ output reg [31:0] outpc = 0,
+ output reg [31:0] outinsn = 0
/* XXX other? */
);
-
-
`ifdef COPY_PASTA_FODDER
/* from page 2 of ARM7TDMIvE2.pdf */
casex (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????00??????????????????????????: /* ALU */
- 32'b????00010?00????????00001001????: /* Atomic swap */
- 32'b????000100101111111111110001????: /* Branch */
- 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 */
- default: /* X everything else out */
+ `DECODE_ALU_MULT: /* Multiply -- must come before ALU, because it pattern matches a specific case of ALU */
+// `DECODE_ALU_MUL_LONG: /* Multiply long */
+ `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 */
+ `DECODE_BRANCH: /* Branch */
+ `DECODE_LDCSTC: /* Coprocessor data transfer */
+ `DECODE_CDP: /* Coprocessor data op */
+ `DECODE_MRCMCR: /* Coprocessor register transfer */
+ `DECODE_SWI: /* SWI */
+ default: /* X everything else out */
endcase
`endif
always @(*)
casez (insn)
- 32'b????000000??????????????1001????: /* 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
use_cpsr = `COND_MATTERS(cond);
use_regs = (insn[21] /* accum */ ? idxbit(rn_mul) : 0) | idxbit(rs_mul) | idxbit(rm);
def_cpsr = insn[20] /* setcc */;
def_regs = idxbit(rd_mul);
end
-// 32'b????00001???????????????1001????: /* Multiply long */
- 32'b????00010?001111????000000000000: /* MRS (Transfer PSR to register) */
+// `DECODE_ALU_MUL_LONG: /* Multiply long */
+ `DECODE_ALU_MRS: /* MRS (Transfer PSR to register) */
begin
use_cpsr = `COND_MATTERS(cond) || (insn[22] == 0) /* Source = CPSR */;
use_regs = 0;
def_cpsr = 0;
def_regs = idxbit(rd);
end
- 32'b????00010?101001111100000000????: /* MSR (Transfer register to PSR) */
+ `DECODE_ALU_MSR: /* MSR (Transfer register to PSR) */
begin
use_cpsr = `COND_MATTERS(cond);
use_regs = idxbit(rm);
def_cpsr = 1;
def_regs = 0;
end
- 32'b????00?10?1010001111????????????: /* MSR (Transfer register or immediate to PSR, flag bits only) */
+ `DECODE_ALU_MSR_FLAGS: /* MSR (Transfer register or immediate to PSR, flag bits only) */
begin
use_cpsr = `COND_MATTERS(cond);
use_regs = insn[25] ? 0 : idxbit(rm);
def_cpsr = 1;
def_regs = 0;
end
- 32'b????00??????????????????????????: /* ALU */
- begin
- use_cpsr = `COND_MATTERS(cond) | (!insn[25] /* I */ && shift_requires_carry(insn[11:4]));
- use_regs =
- (insn[25] /* I */ ? 0 :
- (insn[4] /* shift by reg */ ?
- (idxbit(rs) | idxbit(rm)) :
- (idxbit(rm)))) |
- (((alu_opc != `ALU_MOV) && (alu_opc != `ALU_MVN)) ? idxbit(rn) : 0);
- def_cpsr = insn[20] /* S */ | alu_is_logical(alu_opc);
- def_regs = alu_flags_only(alu_opc) ? 0 : idxbit(rd);
- end
- 32'b????00010?00????????00001001????: /* Atomic swap */
+ `DECODE_ALU_SWP: /* Atomic swap */
begin
use_cpsr = `COND_MATTERS(cond);
use_regs = idxbit(rn) | idxbit(rm);
def_cpsr = 0;
def_regs = idxbit(rd);
end
- 32'b????000100101111111111110001????: /* Branch */
+ `DECODE_ALU_BX: /* Branch */
begin
use_cpsr = `COND_MATTERS(cond);
use_regs = idxbit(rm);
def_cpsr = 0; // don't care, we'll never get there
def_regs = 0;
end
- 32'b????000??0??????????00001??1????: /* Halfword transfer - register offset */
+ `DECODE_ALU_HDATA_REG: /* Halfword transfer - register offset */
begin
use_cpsr = `COND_MATTERS(cond);
use_regs = idxbit(rn) | idxbit(rm) | (insn[20] /* L */ ? 0 : idxbit(rd));
def_cpsr = 0;
def_regs = insn[20] /* L */ ? idxbit(rd) : 0;
end
- 32'b????000??1??????????00001??1????: /* Halfword transfer - immediate offset */
+ `DECODE_ALU_HDATA_IMM: /* Halfword transfer - immediate offset */
begin
use_cpsr = `COND_MATTERS(cond);
use_regs = idxbit(rn) | (insn[20] /* L */ ? 0 : idxbit(rd));
def_cpsr = 0;
def_regs = insn[20] /* L */ ? idxbit(rd) : 0;
end
- 32'b????011????????????????????1????: /* Undefined. I hate ARM */
+ `DECODE_ALU: /* ALU */
+ begin
+ use_cpsr = `COND_MATTERS(cond) | (!insn[25] /* I */ && shift_requires_carry(insn[11:4]));
+ use_regs =
+ (insn[25] /* I */ ? 0 :
+ (insn[4] /* shift by reg */ ?
+ (idxbit(rs) | idxbit(rm)) :
+ (idxbit(rm)))) |
+ (((alu_opc != `ALU_MOV) && (alu_opc != `ALU_MVN)) ? idxbit(rn) : 0);
+ def_cpsr = insn[20] /* S */;
+ def_regs = alu_flags_only(alu_opc) ? 0 : idxbit(rd);
+ end
+ `DECODE_LDRSTR_UNDEFINED: /* Undefined. I hate ARM */
begin
use_cpsr = 0;
use_regs = 0;
def_cpsr = 0;
def_regs = 0;
end
- 32'b????100?????????????????????????: /* Block data transfer */
+ `DECODE_LDRSTR:
+ begin
+ use_cpsr = `COND_MATTERS(cond);
+ use_regs = idxbit(rn) | (insn[25] /* I */ ? idxbit(rm) : 0) | (insn[20] /* L */ ? 0 : idxbit(rd));
+ def_cpsr = 0;
+ def_regs = insn[20] /* L */ ? idxbit(rd) : 0;
+ end
+ `DECODE_LDMSTM: /* Block data transfer */
begin
use_cpsr = `COND_MATTERS(cond);
use_regs = idxbit(rn) | (insn[20] /* L */ ? 0 : insn[15:0]);
def_cpsr = insn[22]; /* This is a superset of all cases, anyway. */
def_regs = (insn[21] /* W */ ? idxbit(rn) : 0) | (insn[20] /* L */ ? insn[15:0] : 0);
end
- 32'b????101?????????????????????????: /* Branch */
+ `DECODE_BRANCH: /* Branch */
begin
use_cpsr = `COND_MATTERS(cond);
use_regs = 0;
def_cpsr = 0;
- def_regs = 0;
+ def_regs = insn[24] /* L */ ? (16'b1 << 14) : 0;
end
- 32'b????110?????????????????????????: /* Coprocessor data transfer */
+ `DECODE_LDCSTC: /* Coprocessor data transfer */
begin
use_cpsr = `COND_MATTERS(cond);
use_regs = idxbit(rn);
def_cpsr = 0;
def_regs = insn[21] /* W */ ? idxbit(rn) : 0;
end
- 32'b????1110???????????????????0????: /* Coprocessor data op */
+ `DECODE_CDP: /* Coprocessor data op */
begin
use_cpsr = `COND_MATTERS(cond);
use_regs = 0;
def_cpsr = 0;
def_regs = 0;
end
- 32'b????1110???????????????????1????: /* Coprocessor register transfer */
+ `DECODE_MRCMCR: /* Coprocessor register transfer */
begin
use_cpsr = `COND_MATTERS(cond);
use_regs = insn[20] /* L */ ? 0 : idxbit(rd);
def_cpsr = 0;
def_regs = insn[20] /* L */ ? idxbit(rd) : 0;
end
- 32'b????1111????????????????????????: /* SWI */
+ `DECODE_SWI: /* SWI */
begin
use_cpsr = `COND_MATTERS(cond);
use_regs = 0;
reg waiting_regs;
wire waiting = waiting_cpsr | waiting_regs;
+ initial
+ begin
+ cpsr_inflight[0] = 0;
+ cpsr_inflight[1] = 0;
+ regs_inflight[0] = 0;
+ regs_inflight[1] = 0;
+ end
+
always @(*)
begin
waiting_cpsr = use_cpsr & (cpsr_inflight[0] | cpsr_inflight[1]);
waiting_regs = |(use_regs & (regs_inflight[0] | regs_inflight[1]));
+
+ outstall = (waiting && !inbubble && !flush) || stall; /* Happens in an always @*, because it is an exception. */
end
-
+
+ reg delayedflush = 0;
+ always @(posedge clk)
+ if (flush && outstall /* halp! I can't do it now, maybe later? */)
+ delayedflush <= 1;
+ else if (!outstall /* anything has been handled this time around */)
+ delayedflush <= 0;
+
/* Actually do the issue. */
- always @(*)
- outstall = waiting;
-
always @(posedge clk)
begin
- cpsr_inflight[0] <= cpsr_inflight[1]; /* I'm not sure how well selects work with arrays, and that seems like a dumb thing to get anusulated by. */
- cpsr_inflight[1] <= (waiting | inbubble) ? 0 : def_cpsr;
- regs_inflight[0] <= regs_inflight[1];
- regs_inflight[1] <= (waiting | inbubble) ? 0 : def_regs;
+ if (waiting)
+ $display("ISSUE: Stalling instruction %08x because %d/%d", insn, waiting_cpsr, waiting_regs);
- outbubble <= inbubble | waiting | !condition_met;
- outpc <= inpc;
- outinsn <= insn;
+ if (!stall)
+ begin
+ cpsr_inflight[0] <= cpsr_inflight[1]; /* I'm not sure how well selects work with arrays, and that seems like a dumb thing to get anusulated by. */
+ cpsr_inflight[1] <= (waiting || inbubble || !condition_met) ? 0 : def_cpsr;
+ regs_inflight[0] <= regs_inflight[1];
+ regs_inflight[1] <= (waiting || inbubble || !condition_met) ? 0 : def_regs;
+
+ outbubble <= inbubble | waiting | !condition_met | flush | delayedflush;
+ outpc <= inpc;
+ outinsn <= insn;
+ end
end
-
endmodule
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