xref: /openbmc/qemu/target/hexagon/decode.c (revision 9e6190ae)
1 /*
2  *  Copyright(c) 2019-2023 Qualcomm Innovation Center, Inc. All Rights Reserved.
3  *
4  *  This program is free software; you can redistribute it and/or modify
5  *  it under the terms of the GNU General Public License as published by
6  *  the Free Software Foundation; either version 2 of the License, or
7  *  (at your option) any later version.
8  *
9  *  This program is distributed in the hope that it will be useful,
10  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
11  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12  *  GNU General Public License for more details.
13  *
14  *  You should have received a copy of the GNU General Public License
15  *  along with this program; if not, see <http://www.gnu.org/licenses/>.
16  */
17 
18 #include "qemu/osdep.h"
19 #include "iclass.h"
20 #include "attribs.h"
21 #include "genptr.h"
22 #include "decode.h"
23 #include "insn.h"
24 #include "printinsn.h"
25 #include "mmvec/decode_ext_mmvec.h"
26 
27 #define fZXTN(N, M, VAL) ((VAL) & ((1LL << (N)) - 1))
28 
29 enum {
30     EXT_IDX_noext = 0,
31     EXT_IDX_noext_AFTER = 4,
32     EXT_IDX_mmvec = 4,
33     EXT_IDX_mmvec_AFTER = 8,
34     XX_LAST_EXT_IDX
35 };
36 
37 /*
38  *  Certain operand types represent a non-contiguous set of values.
39  *  For example, the compound compare-and-jump instruction can only access
40  *  registers R0-R7 and R16-23.
41  *  This table represents the mapping from the encoding to the actual values.
42  */
43 
44 #define DEF_REGMAP(NAME, ELEMENTS, ...) \
45     static const unsigned int DECODE_REGISTER_##NAME[ELEMENTS] = \
46     { __VA_ARGS__ };
47         /* Name   Num Table */
48 DEF_REGMAP(R_16,  16, 0, 1, 2, 3, 4, 5, 6, 7, 16, 17, 18, 19, 20, 21, 22, 23)
49 DEF_REGMAP(R__8,  8,  0, 2, 4, 6, 16, 18, 20, 22)
50 DEF_REGMAP(R_8,   8,  0, 1, 2, 3, 4, 5, 6, 7)
51 
52 #define DECODE_MAPPED_REG(OPNUM, NAME) \
53     insn->regno[OPNUM] = DECODE_REGISTER_##NAME[insn->regno[OPNUM]];
54 
55 /* Helper functions for decode_*_generated.c.inc */
56 #define DECODE_MAPPED(NAME) \
57 static int decode_mapped_reg_##NAME(DisasContext *ctx, int x) \
58 { \
59     return DECODE_REGISTER_##NAME[x]; \
60 }
61 DECODE_MAPPED(R_16)
62 DECODE_MAPPED(R_8)
63 DECODE_MAPPED(R__8)
64 
65 /* Helper function for decodetree_trans_funcs_generated.c.inc */
66 static int shift_left(DisasContext *ctx, int x, int n, int immno)
67 {
68     int ret = x;
69     Insn *insn = ctx->insn;
70     if (!insn->extension_valid ||
71         insn->which_extended != immno) {
72         ret <<= n;
73     }
74     return ret;
75 }
76 
77 /* Include the generated decoder for 32 bit insn */
78 #include "decode_normal_generated.c.inc"
79 #include "decode_hvx_generated.c.inc"
80 
81 /* Include the generated decoder for 16 bit insn */
82 #include "decode_subinsn_a_generated.c.inc"
83 #include "decode_subinsn_l1_generated.c.inc"
84 #include "decode_subinsn_l2_generated.c.inc"
85 #include "decode_subinsn_s1_generated.c.inc"
86 #include "decode_subinsn_s2_generated.c.inc"
87 
88 /* Include the generated helpers for the decoder */
89 #include "decodetree_trans_funcs_generated.c.inc"
90 
91 void decode_send_insn_to(Packet *packet, int start, int newloc)
92 {
93     Insn tmpinsn;
94     int direction;
95     int i;
96     if (start == newloc) {
97         return;
98     }
99     if (start < newloc) {
100         /* Move towards end */
101         direction = 1;
102     } else {
103         /* move towards beginning */
104         direction = -1;
105     }
106     for (i = start; i != newloc; i += direction) {
107         tmpinsn = packet->insn[i];
108         packet->insn[i] = packet->insn[i + direction];
109         packet->insn[i + direction] = tmpinsn;
110     }
111 }
112 
113 /* Fill newvalue registers with the correct regno */
114 static void
115 decode_fill_newvalue_regno(Packet *packet)
116 {
117     int i, use_regidx, offset, def_idx, dst_idx;
118     uint16_t def_opcode, use_opcode;
119     char *dststr;
120 
121     for (i = 1; i < packet->num_insns; i++) {
122         if (GET_ATTRIB(packet->insn[i].opcode, A_DOTNEWVALUE) &&
123             !GET_ATTRIB(packet->insn[i].opcode, A_EXTENSION)) {
124             use_opcode = packet->insn[i].opcode;
125 
126             /* It's a store, so we're adjusting the Nt field */
127             if (GET_ATTRIB(use_opcode, A_STORE)) {
128                 use_regidx = strchr(opcode_reginfo[use_opcode], 't') -
129                     opcode_reginfo[use_opcode];
130             } else {    /* It's a Jump, so we're adjusting the Ns field */
131                 use_regidx = strchr(opcode_reginfo[use_opcode], 's') -
132                     opcode_reginfo[use_opcode];
133             }
134 
135             /*
136              * What's encoded at the N-field is the offset to who's producing
137              * the value.  Shift off the LSB which indicates odd/even register,
138              * then walk backwards and skip over the constant extenders.
139              */
140             offset = packet->insn[i].regno[use_regidx] >> 1;
141             def_idx = i - offset;
142             for (int j = 0; j < offset; j++) {
143                 if (GET_ATTRIB(packet->insn[i - j - 1].opcode, A_IT_EXTENDER)) {
144                     def_idx--;
145                 }
146             }
147 
148             /*
149              * Check for a badly encoded N-field which points to an instruction
150              * out-of-range
151              */
152             g_assert(!((def_idx < 0) || (def_idx > (packet->num_insns - 1))));
153 
154             /*
155              * packet->insn[def_idx] is the producer
156              * Figure out which type of destination it produces
157              * and the corresponding index in the reginfo
158              */
159             def_opcode = packet->insn[def_idx].opcode;
160             dststr = strstr(opcode_wregs[def_opcode], "Rd");
161             if (dststr) {
162                 dststr = strchr(opcode_reginfo[def_opcode], 'd');
163             } else {
164                 dststr = strstr(opcode_wregs[def_opcode], "Rx");
165                 if (dststr) {
166                     dststr = strchr(opcode_reginfo[def_opcode], 'x');
167                 } else {
168                     dststr = strstr(opcode_wregs[def_opcode], "Re");
169                     if (dststr) {
170                         dststr = strchr(opcode_reginfo[def_opcode], 'e');
171                     } else {
172                         dststr = strstr(opcode_wregs[def_opcode], "Ry");
173                         if (dststr) {
174                             dststr = strchr(opcode_reginfo[def_opcode], 'y');
175                         } else {
176                             g_assert_not_reached();
177                         }
178                     }
179                 }
180             }
181             g_assert(dststr != NULL);
182 
183             /* Now patch up the consumer with the register number */
184             dst_idx = dststr - opcode_reginfo[def_opcode];
185             packet->insn[i].regno[use_regidx] =
186                 packet->insn[def_idx].regno[dst_idx];
187             /*
188              * We need to remember who produces this value to later
189              * check if it was dynamically cancelled
190              */
191             packet->insn[i].new_value_producer_slot =
192                 packet->insn[def_idx].slot;
193         }
194     }
195 }
196 
197 /* Split CJ into a compare and a jump */
198 static void decode_split_cmpjump(Packet *pkt)
199 {
200     int last, i;
201     int numinsns = pkt->num_insns;
202 
203     /*
204      * First, split all compare-jumps.
205      * The compare is sent to the end as a new instruction.
206      * Do it this way so we don't reorder dual jumps. Those need to stay in
207      * original order.
208      */
209     for (i = 0; i < numinsns; i++) {
210         /* It's a cmp-jump */
211         if (GET_ATTRIB(pkt->insn[i].opcode, A_NEWCMPJUMP)) {
212             last = pkt->num_insns;
213             pkt->insn[last] = pkt->insn[i];    /* copy the instruction */
214             pkt->insn[last].part1 = true;      /* last insn does the CMP */
215             pkt->insn[i].part1 = false;        /* existing insn does the JUMP */
216             pkt->num_insns++;
217         }
218     }
219 
220     /* Now re-shuffle all the compares back to the beginning */
221     for (i = 0; i < pkt->num_insns; i++) {
222         if (pkt->insn[i].part1) {
223             decode_send_insn_to(pkt, i, 0);
224         }
225     }
226 }
227 
228 static bool decode_opcode_can_jump(int opcode)
229 {
230     if ((GET_ATTRIB(opcode, A_JUMP)) ||
231         (GET_ATTRIB(opcode, A_CALL)) ||
232         (opcode == J2_trap0) ||
233         (opcode == J2_pause)) {
234         /* Exception to A_JUMP attribute */
235         if (opcode == J4_hintjumpr) {
236             return false;
237         }
238         return true;
239     }
240 
241     return false;
242 }
243 
244 static bool decode_opcode_ends_loop(int opcode)
245 {
246     return GET_ATTRIB(opcode, A_HWLOOP0_END) ||
247            GET_ATTRIB(opcode, A_HWLOOP1_END);
248 }
249 
250 /* Set the is_* fields in each instruction */
251 static void decode_set_insn_attr_fields(Packet *pkt)
252 {
253     int i;
254     int numinsns = pkt->num_insns;
255     uint16_t opcode;
256 
257     pkt->pkt_has_cof = false;
258     pkt->pkt_has_multi_cof = false;
259     pkt->pkt_has_endloop = false;
260     pkt->pkt_has_dczeroa = false;
261 
262     for (i = 0; i < numinsns; i++) {
263         opcode = pkt->insn[i].opcode;
264         if (pkt->insn[i].part1) {
265             continue;    /* Skip compare of cmp-jumps */
266         }
267 
268         if (GET_ATTRIB(opcode, A_DCZEROA)) {
269             pkt->pkt_has_dczeroa = true;
270         }
271 
272         if (GET_ATTRIB(opcode, A_STORE)) {
273             if (GET_ATTRIB(opcode, A_SCALAR_STORE) &&
274                 !GET_ATTRIB(opcode, A_MEMSIZE_0B)) {
275                 if (pkt->insn[i].slot == 0) {
276                     pkt->pkt_has_store_s0 = true;
277                 } else {
278                     pkt->pkt_has_store_s1 = true;
279                 }
280             }
281         }
282 
283         if (decode_opcode_can_jump(opcode)) {
284             if (pkt->pkt_has_cof) {
285                 pkt->pkt_has_multi_cof = true;
286             }
287             pkt->pkt_has_cof = true;
288         }
289 
290         pkt->insn[i].is_endloop = decode_opcode_ends_loop(opcode);
291 
292         pkt->pkt_has_endloop |= pkt->insn[i].is_endloop;
293 
294         if (pkt->pkt_has_endloop) {
295             if (pkt->pkt_has_cof) {
296                 pkt->pkt_has_multi_cof = true;
297             }
298             pkt->pkt_has_cof = true;
299         }
300     }
301 }
302 
303 /*
304  * Shuffle for execution
305  * Move stores to end (in same order as encoding)
306  * Move compares to beginning (for use by .new insns)
307  */
308 static void decode_shuffle_for_execution(Packet *packet)
309 {
310     bool changed = false;
311     int i;
312     bool flag;    /* flag means we've seen a non-memory instruction */
313     int n_mems;
314     int last_insn = packet->num_insns - 1;
315 
316     /*
317      * Skip end loops, somehow an end loop is getting in and messing
318      * up the order
319      */
320     if (decode_opcode_ends_loop(packet->insn[last_insn].opcode)) {
321         last_insn--;
322     }
323 
324     do {
325         changed = false;
326         /*
327          * Stores go last, must not reorder.
328          * Cannot shuffle stores past loads, either.
329          * Iterate backwards.  If we see a non-memory instruction,
330          * then a store, shuffle the store to the front.  Don't shuffle
331          * stores wrt each other or a load.
332          */
333         for (flag = false, n_mems = 0, i = last_insn; i >= 0; i--) {
334             int opcode = packet->insn[i].opcode;
335 
336             if (flag && GET_ATTRIB(opcode, A_STORE)) {
337                 decode_send_insn_to(packet, i, last_insn - n_mems);
338                 n_mems++;
339                 changed = true;
340             } else if (GET_ATTRIB(opcode, A_STORE)) {
341                 n_mems++;
342             } else if (GET_ATTRIB(opcode, A_LOAD)) {
343                 /*
344                  * Don't set flag, since we don't want to shuffle a
345                  * store past a load
346                  */
347                 n_mems++;
348             } else if (GET_ATTRIB(opcode, A_DOTNEWVALUE)) {
349                 /*
350                  * Don't set flag, since we don't want to shuffle past
351                  * a .new value
352                  */
353             } else {
354                 flag = true;
355             }
356         }
357 
358         if (changed) {
359             continue;
360         }
361         /* Compares go first, may be reordered wrt each other */
362         for (flag = false, i = 0; i < last_insn + 1; i++) {
363             int opcode = packet->insn[i].opcode;
364 
365             if ((strstr(opcode_wregs[opcode], "Pd4") ||
366                  strstr(opcode_wregs[opcode], "Pe4")) &&
367                 GET_ATTRIB(opcode, A_STORE) == 0) {
368                 /* This should be a compare (not a store conditional) */
369                 if (flag) {
370                     decode_send_insn_to(packet, i, 0);
371                     changed = true;
372                     continue;
373                 }
374             } else if (GET_ATTRIB(opcode, A_IMPLICIT_WRITES_P3) &&
375                        !decode_opcode_ends_loop(packet->insn[i].opcode)) {
376                 /*
377                  * spNloop instruction
378                  * Don't reorder endloops; they are not valid for .new uses,
379                  * and we want to match HW
380                  */
381                 if (flag) {
382                     decode_send_insn_to(packet, i, 0);
383                     changed = true;
384                     continue;
385                 }
386             } else if (GET_ATTRIB(opcode, A_IMPLICIT_WRITES_P0) &&
387                        !GET_ATTRIB(opcode, A_NEWCMPJUMP)) {
388                 if (flag) {
389                     decode_send_insn_to(packet, i, 0);
390                     changed = true;
391                     continue;
392                 }
393             } else {
394                 flag = true;
395             }
396         }
397         if (changed) {
398             continue;
399         }
400     } while (changed);
401 
402     /*
403      * If we have a .new register compare/branch, move that to the very
404      * very end, past stores
405      */
406     for (i = 0; i < last_insn; i++) {
407         if (GET_ATTRIB(packet->insn[i].opcode, A_DOTNEWVALUE)) {
408             decode_send_insn_to(packet, i, last_insn);
409             break;
410         }
411     }
412 }
413 
414 static void
415 apply_extender(Packet *pkt, int i, uint32_t extender)
416 {
417     int immed_num;
418     uint32_t base_immed;
419 
420     immed_num = pkt->insn[i].which_extended;
421     base_immed = pkt->insn[i].immed[immed_num];
422 
423     pkt->insn[i].immed[immed_num] = extender | fZXTN(6, 32, base_immed);
424 }
425 
426 static void decode_apply_extenders(Packet *packet)
427 {
428     int i;
429     for (i = 0; i < packet->num_insns; i++) {
430         if (GET_ATTRIB(packet->insn[i].opcode, A_IT_EXTENDER)) {
431             packet->insn[i + 1].extension_valid = true;
432             apply_extender(packet, i + 1, packet->insn[i].immed[0]);
433         }
434     }
435 }
436 
437 static void decode_remove_extenders(Packet *packet)
438 {
439     int i, j;
440     for (i = 0; i < packet->num_insns; i++) {
441         if (GET_ATTRIB(packet->insn[i].opcode, A_IT_EXTENDER)) {
442             /* Remove this one by moving the remaining instructions down */
443             for (j = i;
444                 (j < packet->num_insns - 1) && (j < INSTRUCTIONS_MAX - 1);
445                 j++) {
446                 packet->insn[j] = packet->insn[j + 1];
447             }
448             packet->num_insns--;
449         }
450     }
451 }
452 
453 static SlotMask get_valid_slots(const Packet *pkt, unsigned int slot)
454 {
455     if (GET_ATTRIB(pkt->insn[slot].opcode, A_EXTENSION)) {
456         return mmvec_ext_decode_find_iclass_slots(pkt->insn[slot].opcode);
457     } else {
458         return find_iclass_slots(pkt->insn[slot].opcode,
459                                  pkt->insn[slot].iclass);
460     }
461 }
462 
463 /*
464  * Section 10.3 of the Hexagon V73 Programmer's Reference Manual
465  *
466  * A duplex is encoded as a 32-bit instruction with bits [15:14] set to 00.
467  * The sub-instructions that comprise a duplex are encoded as 13-bit fields
468  * in the duplex.
469  *
470  * Per table 10-4, the 4-bit duplex iclass is encoded in bits 31:29, 13
471  */
472 static uint32_t get_duplex_iclass(uint32_t encoding)
473 {
474     uint32_t iclass = extract32(encoding, 13, 1);
475     iclass = deposit32(iclass, 1, 3, extract32(encoding, 29, 3));
476     return iclass;
477 }
478 
479 /*
480  * Per table 10-5, the duplex ICLASS field values that specify the group of
481  * each sub-instruction in a duplex
482  *
483  * This table points to the decode instruction for each entry in the table
484  */
485 typedef bool (*subinsn_decode_func)(DisasContext *ctx, uint16_t insn);
486 typedef struct {
487     subinsn_decode_func decode_slot0_subinsn;
488     subinsn_decode_func decode_slot1_subinsn;
489 } subinsn_decode_groups;
490 
491 static const subinsn_decode_groups decode_groups[16] = {
492     [0x0] = { decode_subinsn_l1, decode_subinsn_l1 },
493     [0x1] = { decode_subinsn_l2, decode_subinsn_l1 },
494     [0x2] = { decode_subinsn_l2, decode_subinsn_l2 },
495     [0x3] = { decode_subinsn_a,  decode_subinsn_a },
496     [0x4] = { decode_subinsn_l1, decode_subinsn_a },
497     [0x5] = { decode_subinsn_l2, decode_subinsn_a },
498     [0x6] = { decode_subinsn_s1, decode_subinsn_a },
499     [0x7] = { decode_subinsn_s2, decode_subinsn_a },
500     [0x8] = { decode_subinsn_s1, decode_subinsn_l1 },
501     [0x9] = { decode_subinsn_s1, decode_subinsn_l2 },
502     [0xa] = { decode_subinsn_s1, decode_subinsn_s1 },
503     [0xb] = { decode_subinsn_s2, decode_subinsn_s1 },
504     [0xc] = { decode_subinsn_s2, decode_subinsn_l1 },
505     [0xd] = { decode_subinsn_s2, decode_subinsn_l2 },
506     [0xe] = { decode_subinsn_s2, decode_subinsn_s2 },
507     [0xf] = { NULL,              NULL },              /* Reserved */
508 };
509 
510 static uint16_t get_slot0_subinsn(uint32_t encoding)
511 {
512     return extract32(encoding, 0, 13);
513 }
514 
515 static uint16_t get_slot1_subinsn(uint32_t encoding)
516 {
517     return extract32(encoding, 16, 13);
518 }
519 
520 static unsigned int
521 decode_insns(DisasContext *ctx, Insn *insn, uint32_t encoding)
522 {
523     if (parse_bits(encoding) != 0) {
524         if (decode_normal(ctx, encoding) ||
525             decode_hvx(ctx, encoding)) {
526             insn->generate = opcode_genptr[insn->opcode];
527             insn->iclass = iclass_bits(encoding);
528             return 1;
529         }
530         g_assert_not_reached();
531     } else {
532         uint32_t iclass = get_duplex_iclass(encoding);
533         unsigned int slot0_subinsn = get_slot0_subinsn(encoding);
534         unsigned int slot1_subinsn = get_slot1_subinsn(encoding);
535         subinsn_decode_func decode_slot0_subinsn =
536             decode_groups[iclass].decode_slot0_subinsn;
537         subinsn_decode_func decode_slot1_subinsn =
538             decode_groups[iclass].decode_slot1_subinsn;
539 
540         /* The slot1 subinsn needs to be in the packet first */
541         if (decode_slot1_subinsn(ctx, slot1_subinsn)) {
542             insn->generate = opcode_genptr[insn->opcode];
543             insn->iclass = iclass_bits(encoding);
544             ctx->insn = ++insn;
545             if (decode_slot0_subinsn(ctx, slot0_subinsn)) {
546                 insn->generate = opcode_genptr[insn->opcode];
547                 insn->iclass = iclass_bits(encoding);
548                 return 2;
549             }
550         }
551         g_assert_not_reached();
552     }
553 }
554 
555 static void decode_add_endloop_insn(Insn *insn, int loopnum)
556 {
557     if (loopnum == 10) {
558         insn->opcode = J2_endloop01;
559         insn->generate = opcode_genptr[J2_endloop01];
560     } else if (loopnum == 1) {
561         insn->opcode = J2_endloop1;
562         insn->generate = opcode_genptr[J2_endloop1];
563     } else if (loopnum == 0) {
564         insn->opcode = J2_endloop0;
565         insn->generate = opcode_genptr[J2_endloop0];
566     } else {
567         g_assert_not_reached();
568     }
569 }
570 
571 static bool decode_parsebits_is_loopend(uint32_t encoding32)
572 {
573     uint32_t bits = parse_bits(encoding32);
574     return bits == 0x2;
575 }
576 
577 static bool has_valid_slot_assignment(Packet *pkt)
578 {
579     int used_slots = 0;
580     for (int i = 0; i < pkt->num_insns; i++) {
581         int slot_mask;
582         Insn *insn = &pkt->insn[i];
583         if (decode_opcode_ends_loop(insn->opcode)) {
584             /* We overload slot 0 for endloop. */
585             continue;
586         }
587         slot_mask = 1 << insn->slot;
588         if (used_slots & slot_mask) {
589             return false;
590         }
591         used_slots |= slot_mask;
592     }
593     return true;
594 }
595 
596 static bool
597 decode_set_slot_number(Packet *pkt)
598 {
599     int slot;
600     int i;
601     bool hit_mem_insn = false;
602     bool hit_duplex = false;
603     bool slot0_found = false;
604     bool slot1_found = false;
605     int slot1_iidx = 0;
606 
607     /*
608      * The slots are encoded in reverse order
609      * For each instruction, count down until you find a suitable slot
610      */
611     for (i = 0, slot = 3; i < pkt->num_insns; i++) {
612         SlotMask valid_slots = get_valid_slots(pkt, i);
613 
614         while (!(valid_slots & (1 << slot))) {
615             slot--;
616         }
617         pkt->insn[i].slot = slot;
618         if (slot) {
619             /* I've assigned the slot, now decrement it for the next insn */
620             slot--;
621         }
622     }
623 
624     /* Fix the exceptions - mem insns to slot 0,1 */
625     for (i = pkt->num_insns - 1; i >= 0; i--) {
626         /* First memory instruction always goes to slot 0 */
627         if ((GET_ATTRIB(pkt->insn[i].opcode, A_MEMLIKE) ||
628              GET_ATTRIB(pkt->insn[i].opcode, A_MEMLIKE_PACKET_RULES)) &&
629             !hit_mem_insn) {
630             hit_mem_insn = true;
631             pkt->insn[i].slot = 0;
632             continue;
633         }
634 
635         /* Next memory instruction always goes to slot 1 */
636         if ((GET_ATTRIB(pkt->insn[i].opcode, A_MEMLIKE) ||
637              GET_ATTRIB(pkt->insn[i].opcode, A_MEMLIKE_PACKET_RULES)) &&
638             hit_mem_insn) {
639             pkt->insn[i].slot = 1;
640         }
641     }
642 
643     /* Fix the exceptions - duplex always slot 0,1 */
644     for (i = pkt->num_insns - 1; i >= 0; i--) {
645         /* First subinsn always goes to slot 0 */
646         if (GET_ATTRIB(pkt->insn[i].opcode, A_SUBINSN) && !hit_duplex) {
647             hit_duplex = true;
648             pkt->insn[i].slot = 0;
649             continue;
650         }
651 
652         /* Next subinsn always goes to slot 1 */
653         if (GET_ATTRIB(pkt->insn[i].opcode, A_SUBINSN) && hit_duplex) {
654             pkt->insn[i].slot = 1;
655         }
656     }
657 
658     /* Fix the exceptions - slot 1 is never empty, always aligns to slot 0 */
659     for (i = pkt->num_insns - 1; i >= 0; i--) {
660         /* Is slot0 used? */
661         if (pkt->insn[i].slot == 0) {
662             bool is_endloop = (pkt->insn[i].opcode == J2_endloop01);
663             is_endloop |= (pkt->insn[i].opcode == J2_endloop0);
664             is_endloop |= (pkt->insn[i].opcode == J2_endloop1);
665 
666             /*
667              * Make sure it's not endloop since, we're overloading
668              * slot0 for endloop
669              */
670             if (!is_endloop) {
671                 slot0_found = true;
672             }
673         }
674         /* Is slot1 used? */
675         if (pkt->insn[i].slot == 1) {
676             slot1_found = true;
677             slot1_iidx = i;
678         }
679     }
680     /* Is slot0 empty and slot1 used? */
681     if ((!slot0_found) && slot1_found) {
682         /* Then push it to slot0 */
683         pkt->insn[slot1_iidx].slot = 0;
684     }
685 
686     return has_valid_slot_assignment(pkt);
687 }
688 
689 /*
690  * decode_packet
691  * Decodes packet with given words
692  * Returns 0 on insufficient words,
693  * or number of words used on success
694  */
695 
696 int decode_packet(DisasContext *ctx, int max_words, const uint32_t *words,
697                   Packet *pkt, bool disas_only)
698 {
699     int num_insns = 0;
700     int words_read = 0;
701     bool end_of_packet = false;
702     int new_insns = 0;
703     int i;
704     uint32_t encoding32;
705 
706     /* Initialize */
707     memset(pkt, 0, sizeof(*pkt));
708     /* Try to build packet */
709     while (!end_of_packet && (words_read < max_words)) {
710         Insn *insn = &pkt->insn[num_insns];
711         ctx->insn = insn;
712         encoding32 = words[words_read];
713         end_of_packet = is_packet_end(encoding32);
714         new_insns = decode_insns(ctx, insn, encoding32);
715         g_assert(new_insns > 0);
716         /*
717          * If we saw an extender, mark next word extended so immediate
718          * decode works
719          */
720         if (pkt->insn[num_insns].opcode == A4_ext) {
721             pkt->insn[num_insns + 1].extension_valid = true;
722         }
723         num_insns += new_insns;
724         words_read++;
725     }
726 
727     pkt->num_insns = num_insns;
728     if (!end_of_packet) {
729         /* Ran out of words! */
730         return 0;
731     }
732     pkt->encod_pkt_size_in_bytes = words_read * 4;
733     pkt->pkt_has_hvx = false;
734     for (i = 0; i < num_insns; i++) {
735         pkt->pkt_has_hvx |=
736             GET_ATTRIB(pkt->insn[i].opcode, A_CVI);
737     }
738 
739     /*
740      * Check for :endloop in the parse bits
741      * Section 10.6 of the Programmer's Reference describes the encoding
742      *     The end of hardware loop 0 can be encoded with 2 words
743      *     The end of hardware loop 1 needs 3 words
744      */
745     if ((words_read == 2) && (decode_parsebits_is_loopend(words[0]))) {
746         decode_add_endloop_insn(&pkt->insn[pkt->num_insns++], 0);
747     }
748     if (words_read >= 3) {
749         bool has_loop0, has_loop1;
750         has_loop0 = decode_parsebits_is_loopend(words[0]);
751         has_loop1 = decode_parsebits_is_loopend(words[1]);
752         if (has_loop0 && has_loop1) {
753             decode_add_endloop_insn(&pkt->insn[pkt->num_insns++], 10);
754         } else if (has_loop1) {
755             decode_add_endloop_insn(&pkt->insn[pkt->num_insns++], 1);
756         } else if (has_loop0) {
757             decode_add_endloop_insn(&pkt->insn[pkt->num_insns++], 0);
758         }
759     }
760 
761     decode_apply_extenders(pkt);
762     if (!disas_only) {
763         decode_remove_extenders(pkt);
764         if (!decode_set_slot_number(pkt)) {
765             /* Invalid packet */
766             return 0;
767         }
768     }
769     decode_fill_newvalue_regno(pkt);
770 
771     if (pkt->pkt_has_hvx) {
772         mmvec_ext_decode_checks(pkt, disas_only);
773     }
774 
775     if (!disas_only) {
776         decode_shuffle_for_execution(pkt);
777         decode_split_cmpjump(pkt);
778         decode_set_insn_attr_fields(pkt);
779     }
780 
781     return words_read;
782 }
783 
784 /* Used for "-d in_asm" logging */
785 int disassemble_hexagon(uint32_t *words, int nwords, bfd_vma pc,
786                         GString *buf)
787 {
788     DisasContext ctx;
789     Packet pkt;
790 
791     memset(&ctx, 0, sizeof(DisasContext));
792     ctx.pkt = &pkt;
793 
794     if (decode_packet(&ctx, nwords, words, &pkt, true) > 0) {
795         snprint_a_pkt_disas(buf, &pkt, words, pc);
796         return pkt.encod_pkt_size_in_bytes;
797     } else {
798         g_string_assign(buf, "<invalid>");
799         return 0;
800     }
801 }
802