Memory: Do not progress LSM state machine if rw_wait.
[firearm.git] / Memory.v
1 `include "ARM_Constants.v"
2
3 `define SWP_READING     2'b01
4 `define SWP_WRITING     2'b10
5
6 `define LSRH_MEMIO      3'b001
7 `define LSRH_BASEWB     3'b010
8 `define LSRH_WBFLUSH    3'b100
9
10 `define LSR_MEMIO       4'b0001
11 `define LSR_STRB_WR     4'b0010
12 `define LSR_BASEWB      4'b0100
13 `define LSR_WBFLUSH     4'b1000
14
15 `define LSM_SETUP       4'b0001
16 `define LSM_MEMIO       4'b0010
17 `define LSM_BASEWB      4'b0100
18 `define LSM_WBFLUSH     4'b1000
19
20
21 module Memory(
22         input clk,
23         input Nrst,
24
25         input flush,
26
27         /* bus interface */
28         output reg [31:0] busaddr,
29         output reg rd_req,
30         output reg wr_req,
31         input rw_wait,
32         output reg [31:0] wr_data,
33         input [31:0] rd_data,
34         output reg [2:0] data_size,
35
36         /* regfile interface */
37         output reg [3:0] st_read,
38         input [31:0] st_data,
39         
40         /* Coprocessor interface */
41         output reg cp_req,
42         input cp_ack,
43         input cp_busy,
44         output reg cp_rnw,      /* 1 = read from CP, 0 = write to CP */
45         input [31:0] cp_read,
46         output reg [31:0] cp_write,
47         
48         /* stage inputs */
49         input inbubble,
50         input [31:0] pc,
51         input [31:0] insn,
52         input [31:0] op0,
53         input [31:0] op1,
54         input [31:0] op2,
55         input [31:0] spsr,
56         input [31:0] cpsr,
57         input cpsrup,
58         input write_reg,
59         input [3:0] write_num,
60         input [31:0] write_data,
61
62         /* outputs */
63         output reg outstall,
64         output reg outbubble,
65         output reg [31:0] outpc,
66         output reg [31:0] outinsn,
67         output reg out_write_reg = 1'b0,
68         output reg [3:0] out_write_num = 4'bxxxx,
69         output reg [31:0] out_write_data = 32'hxxxxxxxx,
70         output reg [31:0] outspsr = 32'hxxxxxxxx,
71         output reg [31:0] outcpsr = 32'hxxxxxxxx,
72         output reg outcpsrup = 1'hx
73         );
74
75         reg [31:0] addr, raddr, prev_raddr, next_regdata, next_outcpsr;
76         reg next_outcpsrup;
77         reg [31:0] prevaddr;
78         reg [3:0] next_regsel, cur_reg, prev_reg;
79         reg next_writeback;
80
81         reg next_outbubble;     
82         reg next_write_reg;
83         reg [3:0] next_write_num;
84         reg [31:0] next_write_data;
85
86         reg [3:0] lsr_state = 4'b0001, next_lsr_state;
87         reg [31:0] align_s1, align_s2, align_rddata;
88
89         reg [2:0] lsrh_state = 3'b001, next_lsrh_state;
90         reg [31:0] lsrh_rddata;
91         reg [15:0] lsrh_rddata_s1;
92         reg [7:0] lsrh_rddata_s2;
93
94         reg [15:0] regs, next_regs;
95         reg [3:0] lsm_state = 4'b0001, next_lsm_state;
96         reg [5:0] offset, prev_offset, offset_sel;
97
98         reg [31:0] swp_oldval, next_swp_oldval;
99         reg [1:0] swp_state = 2'b01, next_swp_state;
100         
101         reg do_rd_data_latch;
102         reg [31:0] rd_data_latch = 32'hxxxxxxxx;
103
104         always @(posedge clk)
105         begin
106                 outpc <= pc;
107                 outinsn <= insn;
108                 outbubble <= next_outbubble;
109                 out_write_reg <= next_write_reg;
110                 out_write_num <= next_write_num;
111                 out_write_data <= next_write_data;
112                 if (!rw_wait)
113                         prev_offset <= offset;
114                 prev_raddr <= raddr;
115                 outcpsr <= next_outcpsr;
116                 outspsr <= spsr;
117                 outcpsrup <= next_outcpsrup;
118                 swp_state <= next_swp_state;
119                 lsm_state <= next_lsm_state;
120                 lsr_state <= next_lsr_state;
121                 lsrh_state <= next_lsrh_state;
122                 if (do_rd_data_latch)
123                         rd_data_latch <= rd_data;
124                 prevaddr <= addr;
125         end
126         
127         reg delayedflush = 0;
128         always @(posedge clk)
129                 if (flush && outstall /* halp! I can't do it now, maybe later? */)
130                         delayedflush <= 1;
131                 else if (!outstall /* anything has been handled this time around */)
132                         delayedflush <= 0;
133         
134         /* Drive the state machines and stall. */
135         always @(*)
136         begin
137                 outstall = 1'b0;
138                 next_lsm_state = lsm_state;
139                 next_lsr_state = lsr_state;
140                 next_lsrh_state = lsrh_state;
141                 next_swp_state = swp_state;
142                 casez(insn)
143                 `DECODE_ALU_SWP: if(!inbubble) begin
144                         case(swp_state)
145                         `SWP_READING: begin
146                                 outstall = 1'b1;
147                                 if (!rw_wait)
148                                         next_swp_state = `SWP_WRITING;
149                                 $display("SWP: read stage");
150                         end
151                         `SWP_WRITING: begin
152                                 outstall = rw_wait;
153                                 if(!rw_wait)
154                                         next_swp_state = `SWP_READING;
155                                 $display("SWP: write stage");
156                         end
157                         default: begin
158                                 outstall = 1'bx;
159                                 next_swp_state = 2'bxx;
160                         end
161                         endcase
162                 end
163                 `DECODE_ALU_MULT: begin end
164                 `DECODE_ALU_HDATA_REG,
165                 `DECODE_ALU_HDATA_IMM: if(!inbubble) begin
166                         case(lsrh_state)
167                         `LSRH_MEMIO: begin
168                                 outstall = rw_wait;
169                                 if(insn[21] | !insn[24]) begin
170                                         outstall = 1'b1;
171                                         if(!rw_wait)
172                                                 next_lsrh_state = `LSRH_BASEWB;
173                                 end
174                                 
175                                 if (flush) /* special case! */ begin
176                                         outstall = 1'b0;
177                                         next_lsrh_state = `LSRH_MEMIO;
178                                 end
179                                 
180                                 $display("ALU_LDRSTRH: rd_req %d, wr_req %d", rd_req, wr_req);
181                         end
182                         `LSRH_BASEWB: begin
183                                 outstall = 1'b1;
184                                 next_lsrh_state = `LSRH_WBFLUSH;
185                         end
186                         `LSRH_WBFLUSH: begin
187                                 outstall = 1'b0;
188                                 next_lsrh_state = `LSRH_MEMIO;
189                         end
190                         default: begin
191                                 outstall = 1'bx;
192                                 next_lsrh_state = 3'bxxx;
193                         end
194                         endcase
195                 end
196                 `DECODE_LDRSTR_UNDEFINED: begin end
197                 `DECODE_LDRSTR: if(!inbubble) begin
198                         outstall = rw_wait;
199                         case(lsr_state)
200                         `LSR_MEMIO: begin
201                                 outstall = rw_wait;
202                                 next_lsr_state = `LSR_MEMIO;
203                                 if (insn[22] /* B */ && !insn[20] /* L */) begin        /* i.e., strb */
204                                         outstall = 1'b1;
205                                         if (!rw_wait)
206                                                 next_lsr_state = `LSR_STRB_WR;
207                                 end else if (insn[21] /* W */ || !insn[24] /* P */) begin       /* writeback needed */
208                                         outstall = 1'b1;
209                                         if (!rw_wait)
210                                                 next_lsr_state = `LSR_BASEWB;
211                                 end
212                                 
213                                 if (flush) begin
214                                         outstall = 1'b0;
215                                         next_lsr_state = `LSR_MEMIO;
216                                 end
217                                 $display("LDRSTR: rd_req %d, wr_req %d, raddr %08x, wait %d", rd_req, wr_req, raddr, rw_wait);
218                         end
219                         `LSR_STRB_WR: begin
220                                 outstall = 1;
221                                 if(insn[21] /* W */ | !insn[24] /* P */) begin
222                                         if(!rw_wait)
223                                                 next_lsr_state = `LSR_BASEWB;
224                                 end else if (!rw_wait)
225                                         next_lsr_state = `LSR_WBFLUSH;
226                                 $display("LDRSTR: Handling STRB");
227                         end
228                         `LSR_BASEWB: begin
229                                 outstall = 1;
230                                 next_lsr_state = `LSR_WBFLUSH;
231                         end
232                         `LSR_WBFLUSH: begin
233                                 outstall = 0;
234                                 next_lsr_state = `LSR_MEMIO;
235                         end
236                         default: begin
237                                 outstall = 1'bx;
238                                 next_lsr_state = 4'bxxxx;
239                         end
240                         endcase
241                         $display("LDRSTR: Decoded, bubble %d, insn %08x, lsm state %b -> %b, stall %d", inbubble, insn, lsr_state, next_lsr_state, outstall);
242                 end
243                 `DECODE_LDMSTM: if(!inbubble) begin
244                         outstall = rw_wait;
245                         case(lsm_state)
246                         `LSM_SETUP: begin
247                                 outstall = 1'b1;
248                                 next_lsm_state = `LSM_MEMIO;
249                                 if (flush) begin
250                                         outstall = 1'b0;
251                                         next_lsm_state = `LSM_SETUP;
252                                 end
253                                 $display("LDMSTM: Round 1: base register: %08x, reg list %b", op0, op1[15:0]);
254                         end
255                         `LSM_MEMIO: begin
256                                 outstall = 1'b1;
257                                 if(next_regs == 16'b0 && !rw_wait) begin
258                                         next_lsm_state = `LSM_BASEWB;
259                                 end
260                                 
261                                 $display("LDMSTM: Stage 2: Writing: regs %b, next_regs %b, reg %d, wr_data %08x, addr %08x", regs, next_regs, cur_reg, st_data, busaddr);
262                         end
263                         `LSM_BASEWB: begin
264                                 outstall = 1;
265                                 next_lsm_state = `LSM_WBFLUSH;
266                                 $display("LDMSTM: Stage 3: Writing back");
267                         end
268                         `LSM_WBFLUSH: begin
269                                 outstall = 0;
270                                 next_lsm_state = `LSM_SETUP;
271                         end
272                         default: begin
273                                 outstall = 1'bx;
274                                 next_lsm_state = 4'bxxxx;
275                         end
276                         endcase
277                         $display("LDMSTM: Decoded, bubble %d, insn %08x, lsm state %b -> %b, stall %d", inbubble, insn, lsm_state, next_lsm_state, outstall);
278                 end
279                 `DECODE_LDCSTC: if(!inbubble) begin
280                         $display("WARNING: Unimplemented LDCSTC");
281                 end
282                 `DECODE_CDP: if (!inbubble) begin
283                         if (cp_busy) begin
284                                 outstall = 1;
285                         end
286                         if (!cp_ack) begin
287                                 /* XXX undefined instruction trap */
288                                 $display("WARNING: Possible CDP undefined instruction");
289                         end
290                 end
291                 `DECODE_MRCMCR: if (!inbubble) begin
292                         if (cp_busy) begin
293                                 outstall = 1;
294                         end
295                         if (!cp_ack) begin
296                                 $display("WARNING: Possible MRCMCR undefined instruction: cp_ack %d, cp_busy %d",cp_ack, cp_busy);
297                         end
298                         $display("MRCMCR: ack %d, busy %d", cp_ack, cp_busy);
299                 end
300                 default: begin end
301                 endcase
302         end
303         
304         /* Coprocessor input. */
305         always @(*)
306         begin
307                 cp_req = 0;
308                 cp_rnw = 1'bx;
309                 cp_write = 32'hxxxxxxxx;
310                 casez (insn)
311                 `DECODE_CDP: if(!inbubble) begin
312                         cp_req = 1;
313                 end
314                 `DECODE_MRCMCR: if(!inbubble) begin
315                         cp_req = 1;
316                         cp_rnw = insn[20] /* L */;
317                         if (insn[20] == 0 /* store to coprocessor */)
318                                 cp_write = op0;
319                 end
320                 endcase
321         end
322         
323         /* Register output logic. */
324         always @(*)
325         begin
326                 next_write_reg = write_reg;
327                 next_write_num = write_num;
328                 next_write_data = write_data;
329                 next_outcpsr = lsm_state == 4'b0010 ? outcpsr : cpsr;
330                 next_outcpsrup = cpsrup;
331                 
332                 casez(insn)
333                 `DECODE_ALU_SWP: if (!inbubble) begin
334                         next_write_reg = 1'bx;
335                         next_write_num = 4'bxxxx;
336                         next_write_data = 32'hxxxxxxxx;
337                         case(swp_state)
338                         `SWP_READING:
339                                 next_write_reg = 1'b0;
340                         `SWP_WRITING: begin
341                                 next_write_reg = 1'b1;
342                                 next_write_num = insn[15:12];
343                                 next_write_data = insn[22] ? {24'b0, swp_oldval[7:0]} : swp_oldval;
344                         end
345                         default: begin end
346                         endcase
347                 end
348                 `DECODE_ALU_MULT: begin end
349                 `DECODE_ALU_HDATA_REG,
350                 `DECODE_ALU_HDATA_IMM: if(!inbubble) begin
351                         next_write_reg = 1'bx;
352                         next_write_num = 4'bxxxx;
353                         next_write_data = 32'hxxxxxxxx;
354                         case(lsrh_state)
355                         `LSRH_MEMIO: begin
356                                 next_write_num = insn[15:12];
357                                 next_write_data = lsrh_rddata;
358                                 if(insn[20]) begin
359                                         next_write_reg = 1'b1;
360                                 end
361                         end
362                         `LSRH_BASEWB: begin
363                                 next_write_reg = 1'b1;
364                                 next_write_num = insn[19:16];
365                                 next_write_data = addr;
366                         end
367                         `LSRH_WBFLUSH:
368                                 next_write_reg = 1'b0;
369                         default: begin end
370                         endcase
371                 end
372                 `DECODE_LDRSTR_UNDEFINED: begin end
373                 `DECODE_LDRSTR: if(!inbubble) begin
374                         next_write_reg = 1'bx;
375                         next_write_num = 4'bxxxx;
376                         next_write_data = 32'hxxxxxxxx;
377                         case(lsr_state)
378                         `LSR_MEMIO: begin
379                                 next_write_reg = insn[20] /* L */;
380                                 next_write_num = insn[15:12];
381                                 if(insn[20] /* L */) begin
382                                         next_write_data = insn[22] /* B */ ? {24'h0, align_rddata[7:0]} : align_rddata;
383                                 end
384                         end
385                         `LSR_STRB_WR:
386                                 next_write_reg = 1'b0;
387                         `LSR_BASEWB: begin
388                                 next_write_reg = 1'b1;
389                                 next_write_num = insn[19:16];
390                                 next_write_data = addr;
391                         end
392                         `LSR_WBFLUSH:
393                                 next_write_reg = 1'b0;
394                         default: begin end
395                         endcase
396                 end
397                 `DECODE_LDMSTM: if(!inbubble) begin
398                         next_write_reg = 1'bx;
399                         next_write_num = 4'bxxxx;
400                         next_write_data = 32'hxxxxxxxx;
401                         case(lsm_state)
402                         `LSM_SETUP:
403                                 next_write_reg = 1'b0;
404                         `LSM_MEMIO: begin
405                                 if(insn[20] /* L */) begin
406                                         next_write_reg = !rw_wait;
407                                         next_write_num = cur_reg;
408                                         next_write_data = rd_data;
409                                 end else
410                                         next_write_reg = 1'b0;
411                         end
412                         `LSM_BASEWB: begin
413                                 next_write_reg = insn[21] /* writeback */;
414                                 next_write_num = insn[19:16];
415                                 next_write_data = insn[23] ? op0 + {26'b0, prev_offset} : op0 - {26'b0, prev_offset};
416                                 if(cur_reg == 4'hF && insn[22]) begin
417                                         next_outcpsr = spsr;
418                                         next_outcpsrup = 1;
419                                 end
420                         end
421                         `LSM_WBFLUSH:
422                                 next_write_reg = 1'b0;
423                         default: begin end
424                         endcase
425                 end
426                 `DECODE_MRCMCR: if(!inbubble) begin
427                         next_write_reg = 1'bx;
428                         next_write_num = 4'bxxxx;
429                         next_write_data = 32'hxxxxxxxx;
430                         next_outcpsr = 32'hxxxxxxxx;
431                         next_outcpsrup = 1'bx;
432                         if (insn[20] == 1 /* load from coprocessor */)
433                                 if (insn[15:12] != 4'hF /* Fuck you ARM */) begin
434                                         next_write_reg = 1'b1;
435                                         next_write_num = insn[15:12];
436                                         next_write_data = cp_read;
437                                 end else begin
438                                         next_outcpsr = {cp_read[31:28], cpsr[27:0]};
439                                         next_outcpsrup = 1;
440                                 end
441                 end
442                 endcase
443         end
444         
445         /* Bus/address control logic. */
446         always @(*)
447         begin
448                 rd_req = 1'b0;
449                 wr_req = 1'b0;
450                 offset = prev_offset;
451                 addr = prevaddr;
452                 raddr = 32'hxxxxxxxx;
453                 busaddr = 32'hxxxxxxxx;
454                 data_size = 3'bxxx;
455                 
456                 casez(insn)
457                 `DECODE_ALU_SWP: if(!inbubble) begin
458                         busaddr = {op0[31:2], 2'b0};
459                         data_size = insn[22] ? 3'b001 : 3'b100;
460                         case(swp_state)
461                         `SWP_READING:
462                                 rd_req = 1'b1;
463                         `SWP_WRITING:
464                                 wr_req = 1'b1;
465                         default: begin end
466                         endcase
467                 end
468                 `DECODE_ALU_MULT: begin end
469                 `DECODE_ALU_HDATA_REG,
470                 `DECODE_ALU_HDATA_IMM: if(!inbubble) begin
471                         addr = insn[23] ? op0 + op1 : op0 - op1; /* up/down select */
472                         raddr = insn[24] ? op0 : addr; /* pre/post increment */
473                         busaddr = raddr;
474                         /* rotate to correct position */
475                         case(insn[6:5])
476                         2'b01: /* unsigned half */
477                                 data_size = 3'b010;
478                         2'b10: /* signed byte */
479                                 data_size = 3'b001;
480                         2'b11: /* signed half */
481                                 data_size = 3'b010;
482                         default: begin
483                                 data_size = 3'bxxx;
484                         end
485                         endcase
486                         
487                         case(lsrh_state)
488                         `LSRH_MEMIO: begin
489                                 rd_req = insn[20];
490                                 wr_req = ~insn[20];
491                         end
492                         `LSRH_BASEWB: begin end
493                         `LSRH_WBFLUSH: begin end
494                         default: begin end
495                         endcase
496                 end
497                 `DECODE_LDRSTR_UNDEFINED: begin end
498                 `DECODE_LDRSTR: if(!inbubble) begin
499                         addr = insn[23] ? op0 + op1 : op0 - op1; /* up/down select */
500                         raddr = insn[24] ? addr : op0; /* pre/post increment */
501                         busaddr = raddr;
502                         data_size = insn[22] ? 3'b001 : 3'b100;
503                         case (lsr_state)
504                         `LSR_MEMIO: begin
505                                 rd_req = insn[20] /* L */ || insn[22] /* B */;
506                                 wr_req = !insn[20] /* L */ && !insn[22]/* B */;
507                         end
508                         `LSR_STRB_WR:
509                                 wr_req = 1;
510                         `LSR_BASEWB: begin end
511                         `LSR_WBFLUSH: begin end
512                         default: begin end
513                         endcase
514                 end
515                 `DECODE_LDMSTM: if (!inbubble) begin
516                         data_size = 3'b100;
517                         case (lsm_state)
518                         `LSM_SETUP:
519                                 offset = 6'b0;
520                         `LSM_MEMIO: begin
521                                 rd_req = insn[20];
522                                 wr_req = ~insn[20];
523                                 offset = prev_offset + 6'h4;
524                                 offset_sel = insn[24] ? offset : prev_offset;
525                                 raddr = insn[23] ? op0 + {26'b0, offset_sel} : op0 - {26'b0, offset_sel};
526                                 busaddr = raddr;
527                         end
528                         `LSM_BASEWB: begin end
529                         `LSM_WBFLUSH: begin end
530                         default: begin end
531                         endcase
532                 end
533                 `DECODE_LDCSTC: begin end
534                 `DECODE_CDP: begin end
535                 `DECODE_MRCMCR: begin end
536                 default: begin end
537                 endcase
538         end
539         
540         /* Bus data control logic. */
541         always @(*)
542         begin
543                 wr_data = 32'hxxxxxxxx;
544                 
545                 casez(insn)
546                 `DECODE_ALU_SWP: if(!inbubble)
547                         if (swp_state == `SWP_WRITING)
548                                 wr_data = insn[22] ? {4{op1[7:0]}} : op1;
549                 `DECODE_ALU_MULT: begin end
550                 `DECODE_ALU_HDATA_REG,
551                 `DECODE_ALU_HDATA_IMM: if(!inbubble)
552                         case(insn[6:5])
553                         2'b01: /* unsigned half */
554                                 wr_data = {2{op2[15:0]}}; /* XXX need to store halfword */
555                         2'b10: /* signed byte */
556                                 wr_data = {4{op2[7:0]}};
557                         2'b11: /* signed half */
558                                 wr_data = {2{op2[15:0]}};
559                         default: begin end
560                         endcase
561                 `DECODE_LDRSTR_UNDEFINED: begin end
562                 `DECODE_LDRSTR: if(!inbubble) begin
563                         wr_data = insn[22] ? {24'h0, {op2[7:0]}} : op2;
564                         if (lsr_state == `LSR_STRB_WR)
565                                 case (busaddr[1:0])
566                                 2'b00: wr_data = {rd_data_latch[31:8], op2[7:0]};
567                                 2'b01: wr_data = {rd_data_latch[31:16], op2[7:0], rd_data_latch[7:0]};
568                                 2'b10: wr_data = {rd_data_latch[31:24], op2[7:0], rd_data_latch[15:0]};
569                                 2'b11: wr_data = {op2[7:0], rd_data_latch[23:0]};
570                                 endcase
571                 end
572                 `DECODE_LDMSTM: if (!inbubble)
573                         if (lsm_state == `LSM_MEMIO)
574                                 wr_data = (cur_reg == 4'hF) ? (pc + 12) : st_data;
575                 `DECODE_LDCSTC: begin end
576                 `DECODE_CDP: begin end
577                 `DECODE_MRCMCR: begin end
578                 default: begin end
579                 endcase
580         end
581         
582         /* LDM/STM register control logic. */
583         always @(posedge clk)
584                 if (!rw_wait || lsm_state != `LSM_MEMIO)
585                 begin
586                         prev_reg <= cur_reg;
587                         regs <= next_regs;
588                 end
589         
590         always @(*)
591         begin
592                 st_read = 4'hx;
593                 cur_reg = prev_reg;
594                 next_regs = regs;
595                 
596                 casez(insn)
597                 `DECODE_LDMSTM: if(!inbubble) begin
598                         case(lsm_state)
599                         `LSM_SETUP:
600                                 next_regs = insn[23] /* U */ ? op1[15:0] : {op1[0], op1[1], op1[2], op1[3], op1[4], op1[5], op1[6], op1[7],
601                                                                             op1[8], op1[9], op1[10], op1[11], op1[12], op1[13], op1[14], op1[15]};
602                         `LSM_MEMIO: begin
603                                 casez(regs)
604                                 16'b???????????????1: begin
605                                         cur_reg = 4'h0;
606                                         next_regs = {regs[15:1], 1'b0};
607                                 end
608                                 16'b??????????????10: begin
609                                         cur_reg = 4'h1;
610                                         next_regs = {regs[15:2], 2'b0};
611                                 end
612                                 16'b?????????????100: begin
613                                         cur_reg = 4'h2;
614                                         next_regs = {regs[15:3], 3'b0};
615                                 end
616                                 16'b????????????1000: begin
617                                         cur_reg = 4'h3;
618                                         next_regs = {regs[15:4], 4'b0};
619                                 end
620                                 16'b???????????10000: begin
621                                         cur_reg = 4'h4;
622                                         next_regs = {regs[15:5], 5'b0};
623                                 end
624                                 16'b??????????100000: begin
625                                         cur_reg = 4'h5;
626                                         next_regs = {regs[15:6], 6'b0};
627                                 end
628                                 16'b?????????1000000: begin
629                                         cur_reg = 4'h6;
630                                         next_regs = {regs[15:7], 7'b0};
631                                 end
632                                 16'b????????10000000: begin
633                                         cur_reg = 4'h7;
634                                         next_regs = {regs[15:8], 8'b0};
635                                 end
636                                 16'b???????100000000: begin
637                                         cur_reg = 4'h8;
638                                         next_regs = {regs[15:9], 9'b0};
639                                 end
640                                 16'b??????1000000000: begin
641                                         cur_reg = 4'h9;
642                                         next_regs = {regs[15:10], 10'b0};
643                                 end
644                                 16'b?????10000000000: begin
645                                         cur_reg = 4'hA;
646                                         next_regs = {regs[15:11], 11'b0};
647                                 end
648                                 16'b????100000000000: begin
649                                         cur_reg = 4'hB;
650                                         next_regs = {regs[15:12], 12'b0};
651                                 end
652                                 16'b???1000000000000: begin
653                                         cur_reg = 4'hC;
654                                         next_regs = {regs[15:13], 13'b0};
655                                 end
656                                 16'b??10000000000000: begin
657                                         cur_reg = 4'hD;
658                                         next_regs = {regs[15:14], 14'b0};
659                                 end
660                                 16'b?100000000000000: begin
661                                         cur_reg = 4'hE;
662                                         next_regs = {regs[15], 15'b0};
663                                 end
664                                 16'b1000000000000000: begin
665                                         cur_reg = 4'hF;
666                                         next_regs = 16'b0;
667                                 end
668                                 default: begin
669                                         cur_reg = 4'hx;
670                                         next_regs = 16'b0;
671                                 end
672                                 endcase
673                                 cur_reg = insn[23] ? cur_reg : 4'hF - cur_reg;
674                                 
675                                 st_read = cur_reg;
676                         end
677                         `LSM_BASEWB: begin end
678                         `LSM_WBFLUSH: begin end
679                         default: begin end
680                         endcase
681                 end
682                 endcase
683         end
684         
685         always @(*)
686         begin
687                 do_rd_data_latch = 0;
688                 
689                 next_outbubble = inbubble;
690                 
691                 lsrh_rddata = 32'hxxxxxxxx;
692                 lsrh_rddata_s1 = 16'hxxxx;
693                 lsrh_rddata_s2 = 8'hxx;
694                 next_swp_oldval = swp_oldval;
695
696                 /* XXX shit not given about endianness */
697                 casez(insn)
698                 `DECODE_ALU_SWP: if(!inbubble) begin
699                         next_outbubble = rw_wait;
700                         case(swp_state)
701                         `SWP_READING:
702                                 if(!rw_wait)
703                                         next_swp_oldval = rd_data;
704                         `SWP_WRITING: begin end
705                         default: begin end
706                         endcase
707                 end
708                 `DECODE_ALU_MULT: begin end
709                 `DECODE_ALU_HDATA_REG,
710                 `DECODE_ALU_HDATA_IMM: if(!inbubble) begin
711                         next_outbubble = rw_wait;
712                         
713                         /* rotate to correct position */
714                         case(insn[6:5])
715                         2'b01: begin /* unsigned half */
716                                 lsrh_rddata = {16'b0, raddr[1] ? rd_data[31:16] : rd_data[15:0]};
717                         end
718                         2'b10: begin /* signed byte */
719                                 lsrh_rddata_s1 = raddr[1] ? rd_data[31:16] : rd_data[15:0];
720                                 lsrh_rddata_s2 = raddr[0] ? lsrh_rddata_s1[15:8] : lsrh_rddata_s1[7:0];
721                                 lsrh_rddata = {{24{lsrh_rddata_s2[7]}}, lsrh_rddata_s2};
722                         end
723                         2'b11: begin /* signed half */
724                                 lsrh_rddata = raddr[1] ? {{16{rd_data[31]}}, rd_data[31:16]} : {{16{rd_data[15]}}, rd_data[15:0]};
725                         end
726                         default: begin
727                                 lsrh_rddata = 32'hxxxxxxxx;
728                         end
729                         endcase
730
731                         case(lsrh_state)
732                         `LSRH_MEMIO: begin end
733                         `LSRH_BASEWB:
734                                 next_outbubble = 1'b0;
735                         `LSRH_WBFLUSH: begin end
736                         default: begin end
737                         endcase
738                 end
739                 `DECODE_LDRSTR_UNDEFINED: begin end
740                 `DECODE_LDRSTR: if(!inbubble) begin
741                         next_outbubble = rw_wait;
742                         /* rotate to correct position */
743                         align_s1 = raddr[1] ? {rd_data[15:0], rd_data[31:16]} : rd_data;
744                         align_s2 = raddr[0] ? {align_s1[7:0], align_s1[31:8]} : align_s1;
745                         /* select byte or word */
746                         align_rddata = insn[22] ? {24'b0, align_s2[7:0]} : align_s2;
747                         case(lsr_state)
748                         `LSR_MEMIO:
749                                 if (insn[22] /* B */ && !insn[20] /* L */)
750                                         do_rd_data_latch = 1;
751                         `LSR_STRB_WR: begin end
752                         `LSR_BASEWB:
753                                 next_outbubble = 0;
754                         `LSR_WBFLUSH: begin end
755                         default: begin end
756                         endcase
757                 end
758                 /* XXX ldm/stm incorrect in that stupid case where one of the listed regs is the base reg */
759                 `DECODE_LDMSTM: if(!inbubble) begin
760                         next_outbubble = rw_wait;
761                         case(lsm_state)
762                         `LSM_SETUP: begin end
763                         `LSM_MEMIO: begin end
764                         `LSM_BASEWB:
765                                 next_outbubble = 0;
766                         `LSM_WBFLUSH: begin end
767                         default: $stop;
768                         endcase
769                 end
770                 `DECODE_LDCSTC: begin end
771                 `DECODE_CDP: if(!inbubble) begin
772                         if (cp_busy) begin
773                                 next_outbubble = 1;
774                         end
775                 end
776                 `DECODE_MRCMCR: if(!inbubble) begin
777                         if (cp_busy) begin
778                                 next_outbubble = 1;
779                         end
780                 end
781                 default: begin end
782                 endcase
783                 
784                 if ((flush || delayedflush) && !outstall)
785                         next_outbubble = 1'b1;
786         end
787 endmodule
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