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1 63 robfinch
`timescale 1ns / 1ps
2
// ============================================================================
3
//        __
4
//   \\__/ o\    (C) 2006-2022  Robert Finch, Waterloo
5
//    \  __ /    All rights reserved.
6
//     \/_//     robfinch@finitron.ca
7
//       ||
8
//
9
//      cntlz.v
10
//      - count number of leading zeros in a byte
11
//      - count number of leading ones in a byte
12
//      - simple fast approach - lookup table
13
//
14
// BSD 3-Clause License
15
// Redistribution and use in source and binary forms, with or without
16
// modification, are permitted provided that the following conditions are met:
17
//
18
// 1. Redistributions of source code must retain the above copyright notice, this
19
//    list of conditions and the following disclaimer.
20
//
21
// 2. Redistributions in binary form must reproduce the above copyright notice,
22
//    this list of conditions and the following disclaimer in the documentation
23
//    and/or other materials provided with the distribution.
24
//
25
// 3. Neither the name of the copyright holder nor the names of its
26
//    contributors may be used to endorse or promote products derived from
27
//    this software without specific prior written permission.
28
//
29
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
30
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
31
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
32
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
33
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
34
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
35
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
36
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
37
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
38
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39
//
40
// ============================================================================
41
 
42
module cntlz8(
43
        input [7:0] i,
44
        output reg [3:0] o
45
);
46
 
47
        always_comb
48
                case (i)
49
                8'b00000000:    o = 8;
50
                8'b00000001:    o = 7;
51
                8'b00000010:    o = 6;
52
                8'b00000011:    o = 6;
53
                8'b00000100:    o = 5;
54
                8'b00000101:    o = 5;
55
                8'b00000110:    o = 5;
56
                8'b00000111:    o = 5;
57
                8'b00001000:    o = 4;
58
                8'b00001001:    o = 4;
59
                8'b00001010:    o = 4;
60
                8'b00001011:    o = 4;
61
                8'b00001100:    o = 4;
62
                8'b00001101:    o = 4;
63
                8'b00001110:    o = 4;
64
                8'b00001111:    o = 4;
65
 
66
                8'b00010000:    o = 3;
67
                8'b00010001:    o = 3;
68
                8'b00010010:    o = 3;
69
                8'b00010011:    o = 3;
70
                8'b00010100:    o = 3;
71
                8'b00010101:    o = 3;
72
                8'b00010110:    o = 3;
73
                8'b00010111:    o = 3;
74
                8'b00011000:    o = 3;
75
                8'b00011001:    o = 3;
76
                8'b00011010:    o = 3;
77
                8'b00011011:    o = 3;
78
                8'b00011100:    o = 3;
79
                8'b00011101:    o = 3;
80
                8'b00011110:    o = 3;
81
                8'b00011111:    o = 3;
82
 
83
                8'b00100000:    o = 2;
84
                8'b00100001:    o = 2;
85
                8'b00100010:    o = 2;
86
                8'b00100011:    o = 2;
87
                8'b00100100:    o = 2;
88
                8'b00100101:    o = 2;
89
                8'b00100110:    o = 2;
90
                8'b00100111:    o = 2;
91
                8'b00101000:    o = 2;
92
                8'b00101001:    o = 2;
93
                8'b00101010:    o = 2;
94
                8'b00101011:    o = 2;
95
                8'b00101100:    o = 2;
96
                8'b00101101:    o = 2;
97
                8'b00101110:    o = 2;
98
                8'b00101111:    o = 2;
99
 
100
                8'b00110000:    o = 2;
101
                8'b00110001:    o = 2;
102
                8'b00110010:    o = 2;
103
                8'b00110011:    o = 2;
104
                8'b00110100:    o = 2;
105
                8'b00110101:    o = 2;
106
                8'b00110110:    o = 2;
107
                8'b00110111:    o = 2;
108
                8'b00111000:    o = 2;
109
                8'b00111001:    o = 2;
110
                8'b00111010:    o = 2;
111
                8'b00111011:    o = 2;
112
                8'b00111100:    o = 2;
113
                8'b00111101:    o = 2;
114
                8'b00111110:    o = 2;
115
                8'b00111111:    o = 2;
116
 
117
                // 44 - 1
118
                8'b01000000:    o = 1;
119
                8'b01000001:    o = 1;
120
                8'b01000010:    o = 1;
121
                8'b01000011:    o = 1;
122
                8'b01000100:    o = 1;
123
                8'b01000101:    o = 1;
124
                8'b01000110:    o = 1;
125
                8'b01000111:    o = 1;
126
                8'b01001000:    o = 1;
127
                8'b01001001:    o = 1;
128
                8'b01001010:    o = 1;
129
                8'b01001011:    o = 1;
130
                8'b01001100:    o = 1;
131
                8'b01001101:    o = 1;
132
                8'b01001110:    o = 1;
133
                8'b01001111:    o = 1;
134
 
135
                8'b01010000:    o = 1;
136
                8'b01010001:    o = 1;
137
                8'b01010010:    o = 1;
138
                8'b01010011:    o = 1;
139
                8'b01010100:    o = 1;
140
                8'b01010101:    o = 1;
141
                8'b01010110:    o = 1;
142
                8'b01010111:    o = 1;
143
                8'b01011000:    o = 1;
144
                8'b01011001:    o = 1;
145
                8'b01011010:    o = 1;
146
                8'b01011011:    o = 1;
147
                8'b01011100:    o = 1;
148
                8'b01011101:    o = 1;
149
                8'b01011110:    o = 1;
150
                8'b01011111:    o = 1;
151
 
152
                8'b01100000:    o = 1;
153
                8'b01100001:    o = 1;
154
                8'b01100010:    o = 1;
155
                8'b01100011:    o = 1;
156
                8'b01100100:    o = 1;
157
                8'b01100101:    o = 1;
158
                8'b01100110:    o = 1;
159
                8'b01100111:    o = 1;
160
                8'b01101000:    o = 1;
161
                8'b01101001:    o = 1;
162
                8'b01101010:    o = 1;
163
                8'b01101011:    o = 1;
164
                8'b01101100:    o = 1;
165
                8'b01101101:    o = 1;
166
                8'b01101110:    o = 1;
167
                8'b01101111:    o = 1;
168
 
169
                8'b01110000:    o = 1;
170
                8'b01110001:    o = 1;
171
                8'b01110010:    o = 1;
172
                8'b01110011:    o = 1;
173
                8'b01110100:    o = 1;
174
                8'b01110101:    o = 1;
175
                8'b01110110:    o = 1;
176
                8'b01110111:    o = 1;
177
                8'b01111000:    o = 1;
178
                8'b01111001:    o = 1;
179
                8'b01111010:    o = 1;
180
                8'b01111011:    o = 1;
181
                8'b01111100:    o = 1;
182
                8'b01111101:    o = 1;
183
                8'b01111110:    o = 1;
184
                8'b01111111:    o = 1;
185
 
186
                //  - 2
187
                8'b10000000:    o = 0;
188
                8'b10000001:    o = 0;
189
                8'b10000010:    o = 0;
190
                8'b10000011:    o = 0;
191
                8'b10000100:    o = 0;
192
                8'b10000101:    o = 0;
193
                8'b10000110:    o = 0;
194
                8'b10000111:    o = 0;
195
                8'b10001000:    o = 0;
196
                8'b10001001:    o = 0;
197
                8'b10001010:    o = 0;
198
                8'b10001011:    o = 0;
199
                8'b10001100:    o = 0;
200
                8'b10001101:    o = 0;
201
                8'b10001110:    o = 0;
202
                8'b10001111:    o = 0;
203
 
204
                8'b10010000:    o = 0;
205
                8'b10010001:    o = 0;
206
                8'b10010010:    o = 0;
207
                8'b10010011:    o = 0;
208
                8'b10010100:    o = 0;
209
                8'b10010101:    o = 0;
210
                8'b10010110:    o = 0;
211
                8'b10010111:    o = 0;
212
                8'b10011000:    o = 0;
213
                8'b10011001:    o = 0;
214
                8'b10011010:    o = 0;
215
                8'b10011011:    o = 0;
216
                8'b10011100:    o = 0;
217
                8'b10011101:    o = 0;
218
                8'b10011110:    o = 0;
219
                8'b10011111:    o = 0;
220
 
221
                8'b10100000:    o = 0;
222
                8'b10100001:    o = 0;
223
                8'b10100010:    o = 0;
224
                8'b10100011:    o = 0;
225
                8'b10100100:    o = 0;
226
                8'b10100101:    o = 0;
227
                8'b10100110:    o = 0;
228
                8'b10100111:    o = 0;
229
                8'b10101000:    o = 0;
230
                8'b10101001:    o = 0;
231
                8'b10101010:    o = 0;
232
                8'b10101011:    o = 0;
233
                8'b10101100:    o = 0;
234
                8'b10101101:    o = 0;
235
                8'b10101110:    o = 0;
236
                8'b10101111:    o = 0;
237
 
238
                8'b10110000:    o = 0;
239
                8'b10110001:    o = 0;
240
                8'b10110010:    o = 0;
241
                8'b10110011:    o = 0;
242
                8'b10110100:    o = 0;
243
                8'b10110101:    o = 0;
244
                8'b10110110:    o = 0;
245
                8'b10110111:    o = 0;
246
                8'b10111000:    o = 0;
247
                8'b10111001:    o = 0;
248
                8'b10111010:    o = 0;
249
                8'b10111011:    o = 0;
250
                8'b10111100:    o = 0;
251
                8'b10111101:    o = 0;
252
                8'b10111110:    o = 0;
253
                8'b10111111:    o = 0;
254
 
255
                // 44 - 3
256
                8'b11000000:    o = 0;
257
                8'b11000001:    o = 0;
258
                8'b11000010:    o = 0;
259
                8'b11000011:    o = 0;
260
                8'b11000100:    o = 0;
261
                8'b11000101:    o = 0;
262
                8'b11000110:    o = 0;
263
                8'b11000111:    o = 0;
264
                8'b11001000:    o = 0;
265
                8'b11001001:    o = 0;
266
                8'b11001010:    o = 0;
267
                8'b11001011:    o = 0;
268
                8'b11001100:    o = 0;
269
                8'b11001101:    o = 0;
270
                8'b11001110:    o = 0;
271
                8'b11001111:    o = 0;
272
 
273
                8'b11010000:    o = 0;
274
                8'b11010001:    o = 0;
275
                8'b11010010:    o = 0;
276
                8'b11010011:    o = 0;
277
                8'b11010100:    o = 0;
278
                8'b11010101:    o = 0;
279
                8'b11010110:    o = 0;
280
                8'b11010111:    o = 0;
281
                8'b11011000:    o = 0;
282
                8'b11011001:    o = 0;
283
                8'b11011010:    o = 0;
284
                8'b11011011:    o = 0;
285
                8'b11011100:    o = 0;
286
                8'b11011101:    o = 0;
287
                8'b11011110:    o = 0;
288
                8'b11011111:    o = 0;
289
 
290
                8'b11100000:    o = 0;
291
                8'b11100001:    o = 0;
292
                8'b11100010:    o = 0;
293
                8'b11100011:    o = 0;
294
                8'b11100100:    o = 0;
295
                8'b11100101:    o = 0;
296
                8'b11100110:    o = 0;
297
                8'b11100111:    o = 0;
298
                8'b11101000:    o = 0;
299
                8'b11101001:    o = 0;
300
                8'b11101010:    o = 0;
301
                8'b11101011:    o = 0;
302
                8'b11101100:    o = 0;
303
                8'b11101101:    o = 0;
304
                8'b11101110:    o = 0;
305
                8'b11101111:    o = 0;
306
 
307
                8'b11110000:    o = 0;
308
                8'b11110001:    o = 0;
309
                8'b11110010:    o = 0;
310
                8'b11110011:    o = 0;
311
                8'b11110100:    o = 0;
312
                8'b11110101:    o = 0;
313
                8'b11110110:    o = 0;
314
                8'b11110111:    o = 0;
315
                8'b11111000:    o = 0;
316
                8'b11111001:    o = 0;
317
                8'b11111010:    o = 0;
318
                8'b11111011:    o = 0;
319
                8'b11111100:    o = 0;
320
                8'b11111101:    o = 0;
321
                8'b11111110:    o = 0;
322
                8'b11111111:    o = 0;
323
 
324
                endcase
325
 
326
 
327
endmodule
328
 
329
 
330
module cntlz16(
331
        input [15:0] i,
332
        output [4:0] o
333
);
334
 
335
        wire [3:0] cnt1, cnt2;
336
 
337
        cntlz8 u1 (i[ 7:0],cnt1);
338
        cntlz8 u2 (i[15:8],cnt2);
339
 
340
        assign o = cnt2[3] ? cnt1 + 4'h8 : cnt2;
341
 
342
endmodule
343
 
344
 
345
// 39 slices / 67 LUTs / 19.3ns
346
module cntlz24(
347
        input [23:0] i,
348
        output [4:0] o
349
);
350
 
351
        wire [3:0] cnt1, cnt2, cnt3;
352
 
353
        // cntlz8 results in faster result than cntlz16
354
        cntlz8 u1 (i[ 7: 0],cnt1);
355
        cntlz8 u2 (i[15: 8],cnt2);
356
        cntlz8 u3 (i[23:16],cnt3);
357
 
358
        assign o =
359
                !cnt3[3] ? cnt3 :
360
                !cnt2[3] ? cnt2 + 5'd8 :
361
                 cnt1 + 5'd16;
362
 
363
endmodule
364
 
365
// 39 slices / 67 LUTs / 19.3ns
366
module cntlz32(
367
        input [31:0] i,
368
        output [5:0] o
369
);
370
 
371
        wire [3:0] cnt1, cnt2, cnt3, cnt4;
372
 
373
        // cntlz8 results in faster result than cntlz16
374
        cntlz8 u1 (i[ 7: 0],cnt1);
375
        cntlz8 u2 (i[15: 8],cnt2);
376
        cntlz8 u3 (i[23:16],cnt3);
377
        cntlz8 u4 (i[31:24],cnt4);
378
 
379
        assign o =
380
                !cnt4[3] ? cnt4 :
381
                !cnt3[3] ? cnt3 + 6'd8 :
382
                !cnt2[3] ? cnt2 + 6'd16 :
383
                 cnt1 + 6'd24;
384
 
385
endmodule
386
 
387
 
388
// 88 slices / 154 LUTs / 22.5 ns
389
module cntlz48(
390
        input [47:0] i,
391
        output [5:0] o
392
);
393
 
394
        wire [4:0] cnt1, cnt2, cnt3;
395
 
396
        cntlz16 u1 (i[15: 0],cnt1);
397
        cntlz16 u2 (i[31:16],cnt2);
398
        cntlz16 u3 (i[47:32],cnt3);
399
 
400
        assign o =
401
                !cnt3[4] ? cnt3 :
402
                !cnt2[4] ? cnt2 + 7'd16 :
403
                 cnt1 + 7'd32;
404
 
405
endmodule
406
 
407
 
408
// 88 slices / 154 LUTs / 22.5 ns
409
module cntlz64(
410
        input [63:0] i,
411
        output [6:0] o
412
);
413
 
414
        wire [4:0] cnt1, cnt2, cnt3, cnt4;
415
 
416
        cntlz16 u1 (i[15: 0],cnt1);
417
        cntlz16 u2 (i[31:16],cnt2);
418
        cntlz16 u3 (i[47:32],cnt3);
419
        cntlz16 u4 (i[63:48],cnt4);
420
 
421
        assign o =
422
                !cnt4[4] ? cnt4 :
423
                !cnt3[4] ? cnt3 + 7'd16 :
424
                !cnt2[4] ? cnt2 + 7'd32 :
425
                 cnt1 + 7'd48;
426
 
427
endmodule
428
 
429
 
430
module cntlz80(
431
        input [79:0] i,
432
        output [6:0] o
433
);
434
 
435
    wire [4:0] cnt3;
436
        wire [5:0] cnt1, cnt2;
437
 
438
        cntlz32 u1 (i[31: 0],cnt1);
439
        cntlz32 u2 (i[63:32],cnt2);
440
        cntlz16 u3 (i[79:64],cnt3);
441
 
442
        assign o =
443
                !cnt3[4] ? {2'b0,cnt3} :
444
                !cnt2[5] ? {1'b0,cnt2} + 8'd16 :
445
                 {1'b0,cnt1} + 7'd48;
446
 
447
endmodule
448
 
449
 
450
module cntlz96(
451
        input [95:0] i,
452
        output [7:0] o
453
);
454
 
455
        wire [5:0] cnt1, cnt2, cnt3;
456
 
457
        cntlz32 u1 (i[31: 0],cnt1);
458
        cntlz32 u2 (i[63:32],cnt2);
459
        cntlz32 u3 (i[95:64],cnt3);
460
 
461
        assign o =
462
                !cnt3[5] ? cnt3 :
463
                !cnt2[5] ? cnt2 + 8'd32 :
464
                 cnt1 + 8'd64;
465
 
466
endmodule
467
 
468
 
469
module cntlz128(
470
        input [127:0] i,
471
        output [7:0] o
472
);
473
 
474
        wire [5:0] cnt1, cnt2, cnt3, cnt4;
475
 
476
        cntlz32 u1 (i[31: 0],cnt1);
477
        cntlz32 u2 (i[63:32],cnt2);
478
        cntlz32 u3 (i[95:64],cnt3);
479
        cntlz32 u4 (i[127:96],cnt4);
480
 
481
        assign o =
482
                !cnt4[5] ? cnt4 :
483
                !cnt3[5] ? cnt3 + 8'd32 :
484
                !cnt2[5] ? cnt2 + 8'd64 :
485
                 cnt1 + 8'd96;
486
 
487
endmodule
488
 
489
 
490
module cntlz192(
491
        input [191:0] i,
492
        output [7:0] o
493
);
494
 
495
        wire [5:0] cnt1, cnt2, cnt3, cnt4, cnt5, cnt6;
496
 
497
        cntlz32 u1 (i[31: 0],cnt1);
498
        cntlz32 u2 (i[63:32],cnt2);
499
        cntlz32 u3 (i[95:64],cnt3);
500
        cntlz32 u4 (i[127:96],cnt4);
501
        cntlz32 u5 (i[159:128],cnt5);
502
        cntlz32 u6 (i[191:160],cnt6);
503
 
504
        assign o =
505
                !cnt6[5] ? cnt6 :
506
                !cnt5[5] ? cnt5 + 8'd32 :
507
                !cnt4[5] ? cnt4 + 8'd64:
508
                !cnt3[5] ? cnt3 + 8'd96 :
509
                !cnt2[5] ? cnt2 + 8'd128 :
510
                 cnt1 + 8'd160;
511
 
512
endmodule
513
 
514
 
515
module cntlz32Reg(
516
        input clk,
517
        input ce,
518
        input [31:0] i,
519
        output reg [5:0] o
520
);
521
 
522
        wire [5:0] o1;
523
        cntlz32 u1 (i,o1);
524
        always @(posedge clk)
525
                if (ce) o <= o1;
526
 
527
endmodule
528
 
529
 
530
module cntlz64Reg(
531
        input clk,
532
        input ce,
533
        input [63:0] i,
534
        output reg [6:0] o
535
);
536
 
537
        wire [6:0] o1;
538
        cntlz64 u1 (i,o1);
539
        always @(posedge clk)
540
                if (ce) o <= o1;
541
 
542
endmodule
543
 
544
module cntlz80Reg(
545
        input clk,
546
        input ce,
547
        input [79:0] i,
548
        output reg [6:0] o
549
);
550
 
551
        wire [6:0] o1;
552
        cntlz80 u1 (i,o1);
553
        always @(posedge clk)
554
                if (ce) o <= o1;
555
 
556
endmodule
557
 
558
module cntlz96Reg(
559
        input clk,
560
        input ce,
561
        input [95:0] i,
562
        output reg [7:0] o
563
);
564
 
565
        wire [7:0] o1;
566
        cntlz96 u1 (i,o1);
567
        always @(posedge clk)
568
                if (ce) o <= o1;
569
 
570
endmodule
571
 
572
module cntlz128Reg(
573
        input clk,
574
        input ce,
575
        input [127:0] i,
576
        output reg [7:0] o
577
);
578
 
579
        wire [7:0] o1;
580
        cntlz128 u1 (i,o1);
581
        always @(posedge clk)
582
                if (ce) o <= o1;
583
 
584
endmodule
585
 
586
module cntlz192Reg(
587
        input clk,
588
        input ce,
589
        input [191:0] i,
590
        output reg [7:0] o
591
);
592
 
593
        wire [7:0] o1;
594
        cntlz192 u1 (i,o1);
595
        always @(posedge clk)
596
                if (ce) o <= o1;
597
 
598
endmodule
599
 
600
// 5 slices / 10 LUTs / 7.702 ns
601
module cntlo8(
602
        input [7:0] i,
603
        output [3:0] o
604
);
605
 
606
        cntlz8 u1 (~i,o);
607
 
608
endmodule
609
 
610
 
611
module cntlo16(
612
        input [15:0] i,
613
        output [4:0] o
614
);
615
 
616
        cntlz16 u1 (~i,o);
617
 
618
endmodule
619
 
620
 
621
module cntlo32(
622
        input [31:0] i,
623
        output [5:0] o
624
);
625
 
626
        cntlz32 u1 (~i,o);
627
 
628
endmodule
629
 
630
 
631
module cntlo48(
632
        input [47:0] i,
633
        output [5:0] o
634
);
635
 
636
        cntlz48 u1 (~i,o);
637
 
638
endmodule
639
 
640
 
641
// 59 slices / 99 LUTs / 14.065 ns
642
module cntlo64(
643
        input [63:0] i,
644
        output [6:0] o
645
);
646
 
647
        cntlz64 u1 (~i,o);
648
 
649
endmodule
650
 
651
module cntlo80(
652
        input [79:0] i,
653
        output [6:0] o
654
);
655
 
656
        cntlz80 u1 (~i,o);
657
 
658
endmodule
659
 
660
module cntlo128(
661
        input [127:0] i,
662
        output [7:0] o
663
);
664
 
665
        cntlz128 u1 (~i,o);
666
 
667
endmodule
668
 

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