summaryrefslogtreecommitdiffstats
path: root/js/src/jit/JitFrames.cpp
blob: 176b988e050d13c27a79ee04b3e8c238a20b1b35 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=8 sts=2 et sw=2 tw=80:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "jit/JitFrames-inl.h"

#include "mozilla/ScopeExit.h"

#include <algorithm>

#include "builtin/ModuleObject.h"
#include "gc/GC.h"
#include "jit/BaselineFrame.h"
#include "jit/BaselineIC.h"
#include "jit/BaselineJIT.h"
#include "jit/Ion.h"
#include "jit/IonScript.h"
#include "jit/JitRuntime.h"
#include "jit/JitSpewer.h"
#include "jit/LIR.h"
#include "jit/Recover.h"
#include "jit/Safepoints.h"
#include "jit/ScriptFromCalleeToken.h"
#include "jit/Snapshots.h"
#include "jit/VMFunctions.h"
#include "js/Exception.h"
#include "js/friend/DumpFunctions.h"  // js::DumpObject, js::DumpValue
#include "vm/Interpreter.h"
#include "vm/JSContext.h"
#include "vm/JSFunction.h"
#include "vm/JSObject.h"
#include "vm/JSScript.h"
#include "wasm/WasmBuiltins.h"
#include "wasm/WasmInstance.h"

#include "debugger/DebugAPI-inl.h"
#include "jit/JSJitFrameIter-inl.h"
#include "vm/GeckoProfiler-inl.h"
#include "vm/JSScript-inl.h"
#include "vm/Probes-inl.h"

namespace js {
namespace jit {

// Given a slot index, returns the offset, in bytes, of that slot from an
// JitFrameLayout. Slot distances are uniform across architectures, however,
// the distance does depend on the size of the frame header.
static inline int32_t OffsetOfFrameSlot(int32_t slot) { return -slot; }

static inline uint8_t* AddressOfFrameSlot(JitFrameLayout* fp, int32_t slot) {
  return (uint8_t*)fp + OffsetOfFrameSlot(slot);
}

static inline uintptr_t ReadFrameSlot(JitFrameLayout* fp, int32_t slot) {
  return *(uintptr_t*)AddressOfFrameSlot(fp, slot);
}

static inline void WriteFrameSlot(JitFrameLayout* fp, int32_t slot,
                                  uintptr_t value) {
  *(uintptr_t*)AddressOfFrameSlot(fp, slot) = value;
}

static inline double ReadFrameDoubleSlot(JitFrameLayout* fp, int32_t slot) {
  return *(double*)AddressOfFrameSlot(fp, slot);
}

static inline float ReadFrameFloat32Slot(JitFrameLayout* fp, int32_t slot) {
  return *(float*)AddressOfFrameSlot(fp, slot);
}

static inline int32_t ReadFrameInt32Slot(JitFrameLayout* fp, int32_t slot) {
  return *(int32_t*)AddressOfFrameSlot(fp, slot);
}

static inline bool ReadFrameBooleanSlot(JitFrameLayout* fp, int32_t slot) {
  return *(bool*)AddressOfFrameSlot(fp, slot);
}

static uint32_t NumArgAndLocalSlots(const InlineFrameIterator& frame) {
  JSScript* script = frame.script();
  return CountArgSlots(script, frame.maybeCalleeTemplate()) + script->nfixed();
}

static void CloseLiveIteratorIon(JSContext* cx,
                                 const InlineFrameIterator& frame,
                                 const TryNote* tn) {
  MOZ_ASSERT(tn->kind() == TryNoteKind::ForIn ||
             tn->kind() == TryNoteKind::Destructuring);

  bool isDestructuring = tn->kind() == TryNoteKind::Destructuring;
  MOZ_ASSERT_IF(!isDestructuring, tn->stackDepth > 0);
  MOZ_ASSERT_IF(isDestructuring, tn->stackDepth > 1);

  // Save any pending exception, because some recover operations call into
  // AutoUnsafeCallWithABI functions, which don't allow pending exceptions.
  JS::AutoSaveExceptionState savedExc(cx);

  SnapshotIterator si = frame.snapshotIterator();

  // Skip stack slots until we reach the iterator object on the stack. For
  // the destructuring case, we also need to get the "done" value.
  uint32_t stackSlot = tn->stackDepth;
  uint32_t adjust = isDestructuring ? 2 : 1;
  uint32_t skipSlots = NumArgAndLocalSlots(frame) + stackSlot - adjust;

  for (unsigned i = 0; i < skipSlots; i++) {
    si.skip();
  }

  MaybeReadFallback recover(cx, cx->activation()->asJit(), &frame.frame(),
                            MaybeReadFallback::Fallback_DoNothing);
  Value v = si.maybeRead(recover);
  MOZ_RELEASE_ASSERT(v.isObject());
  RootedObject iterObject(cx, &v.toObject());

  if (isDestructuring) {
    RootedValue doneValue(cx, si.read());
    MOZ_RELEASE_ASSERT(!doneValue.isMagic());
    bool done = ToBoolean(doneValue);
    // Do not call IteratorClose if the destructuring iterator is already
    // done.
    if (done) {
      return;
    }
  }

  // Restore any pending exception before the closing the iterator.
  savedExc.restore();

  if (cx->isExceptionPending()) {
    if (tn->kind() == TryNoteKind::ForIn) {
      CloseIterator(iterObject);
    } else {
      IteratorCloseForException(cx, iterObject);
    }
  } else {
    UnwindIteratorForUncatchableException(iterObject);
  }
}

class IonTryNoteFilter {
  uint32_t depth_;

 public:
  explicit IonTryNoteFilter(const InlineFrameIterator& frame) {
    uint32_t base = NumArgAndLocalSlots(frame);
    SnapshotIterator si = frame.snapshotIterator();
    MOZ_ASSERT(si.numAllocations() >= base);
    depth_ = si.numAllocations() - base;
  }

  bool operator()(const TryNote* note) { return note->stackDepth <= depth_; }
};

class TryNoteIterIon : public TryNoteIter<IonTryNoteFilter> {
 public:
  TryNoteIterIon(JSContext* cx, const InlineFrameIterator& frame)
      : TryNoteIter(cx, frame.script(), frame.pc(), IonTryNoteFilter(frame)) {}
};

static bool ShouldBailoutForDebugger(JSContext* cx,
                                     const InlineFrameIterator& frame,
                                     bool hitBailoutException) {
  if (hitBailoutException) {
    MOZ_ASSERT(!cx->isPropagatingForcedReturn());
    return false;
  }

  // Bail out if we're propagating a forced return from an inlined frame,
  // even if the realm is no longer a debuggee.
  if (cx->isPropagatingForcedReturn() && frame.more()) {
    return true;
  }

  if (!cx->realm()->isDebuggee()) {
    return false;
  }

  // Bail out if there's a catchable exception and we are the debuggee of a
  // Debugger with a live onExceptionUnwind hook.
  if (cx->isExceptionPending() &&
      DebugAPI::hasExceptionUnwindHook(cx->global())) {
    return true;
  }

  // Bail out if a Debugger has observed this frame (e.g., for onPop).
  JitActivation* act = cx->activation()->asJit();
  RematerializedFrame* rematFrame =
      act->lookupRematerializedFrame(frame.frame().fp(), frame.frameNo());
  return rematFrame && rematFrame->isDebuggee();
}

static void OnLeaveIonFrame(JSContext* cx, const InlineFrameIterator& frame,
                            ResumeFromException* rfe) {
  bool returnFromThisFrame =
      cx->isPropagatingForcedReturn() || cx->isClosingGenerator();
  if (!returnFromThisFrame) {
    return;
  }

  JitActivation* act = cx->activation()->asJit();
  RematerializedFrame* rematFrame = nullptr;
  {
    JS::AutoSaveExceptionState savedExc(cx);

    // We can run recover instructions without invalidating because we're
    // already leaving the frame.
    MaybeReadFallback::FallbackConsequence consequence =
        MaybeReadFallback::Fallback_DoNothing;
    rematFrame = act->getRematerializedFrame(cx, frame.frame(), frame.frameNo(),
                                             consequence);
    if (!rematFrame) {
      return;
    }
  }

  MOZ_ASSERT(!frame.more());

  if (cx->isClosingGenerator()) {
    HandleClosingGeneratorReturn(cx, rematFrame, /*frameOk=*/true);
  } else {
    cx->clearPropagatingForcedReturn();
  }

  Value& rval = rematFrame->returnValue();
  MOZ_RELEASE_ASSERT(!rval.isMagic());

  // Set both framePointer and stackPointer to the address of the
  // JitFrameLayout.
  rfe->kind = ExceptionResumeKind::ForcedReturnIon;
  rfe->framePointer = frame.frame().fp();
  rfe->stackPointer = frame.frame().fp();
  rfe->exception = rval;
  rfe->exceptionStack = NullValue();

  act->removeIonFrameRecovery(frame.frame().jsFrame());
  act->removeRematerializedFrame(frame.frame().fp());
}

static void HandleExceptionIon(JSContext* cx, const InlineFrameIterator& frame,
                               ResumeFromException* rfe,
                               bool* hitBailoutException) {
  if (ShouldBailoutForDebugger(cx, frame, *hitBailoutException)) {
    // We do the following:
    //
    //   1. Bailout to baseline to reconstruct a baseline frame.
    //   2. Resume immediately into the exception tail afterwards, and
    //      handle the exception again with the top frame now a baseline
    //      frame.
    //
    // An empty exception info denotes that we're propagating an Ion
    // exception due to debug mode, which BailoutIonToBaseline needs to
    // know. This is because we might not be able to fully reconstruct up
    // to the stack depth at the snapshot, as we could've thrown in the
    // middle of a call.
    ExceptionBailoutInfo propagateInfo(cx);
    if (ExceptionHandlerBailout(cx, frame, rfe, propagateInfo)) {
      return;
    }
    *hitBailoutException = true;
  }

  RootedScript script(cx, frame.script());

  for (TryNoteIterIon tni(cx, frame); !tni.done(); ++tni) {
    const TryNote* tn = *tni;
    switch (tn->kind()) {
      case TryNoteKind::ForIn:
      case TryNoteKind::Destructuring:
        CloseLiveIteratorIon(cx, frame, tn);
        break;

      case TryNoteKind::Catch:
        // If we're closing a generator, we have to skip catch blocks.
        if (cx->isClosingGenerator()) {
          break;
        }

        if (cx->isExceptionPending()) {
          // Ion can compile try-catch, but bailing out to catch
          // exceptions is slow. Reset the warm-up counter so that if we
          // catch many exceptions we won't Ion-compile the script.
          script->resetWarmUpCounterToDelayIonCompilation();

          if (*hitBailoutException) {
            break;
          }

          // Bailout at the start of the catch block.
          jsbytecode* catchPC = script->offsetToPC(tn->start + tn->length);
          ExceptionBailoutInfo excInfo(cx, frame.frameNo(), catchPC,
                                       tn->stackDepth);
          if (ExceptionHandlerBailout(cx, frame, rfe, excInfo)) {
            // Record exception locations to allow scope unwinding in
            // |FinishBailoutToBaseline|
            MOZ_ASSERT(cx->isExceptionPending());
            rfe->bailoutInfo->tryPC =
                UnwindEnvironmentToTryPc(frame.script(), tn);
            rfe->bailoutInfo->faultPC = frame.pc();
            return;
          }

          *hitBailoutException = true;
          MOZ_ASSERT(cx->isExceptionPending());
        }
        break;

      case TryNoteKind::Finally: {
        if (!cx->isExceptionPending()) {
          // We don't catch uncatchable exceptions.
          break;
        }

        script->resetWarmUpCounterToDelayIonCompilation();

        if (*hitBailoutException) {
          break;
        }

        // Bailout at the start of the finally block.
        jsbytecode* finallyPC = script->offsetToPC(tn->start + tn->length);
        ExceptionBailoutInfo excInfo(cx, frame.frameNo(), finallyPC,
                                     tn->stackDepth);

        RootedValue exception(cx);
        RootedValue exceptionStack(cx);
        if (!cx->getPendingException(&exception) ||
            !cx->getPendingExceptionStack(&exceptionStack)) {
          exception = UndefinedValue();
          exceptionStack = NullValue();
        }
        excInfo.setFinallyException(exception.get(), exceptionStack.get());
        cx->clearPendingException();

        if (ExceptionHandlerBailout(cx, frame, rfe, excInfo)) {
          // Record exception locations to allow scope unwinding in
          // |FinishBailoutToBaseline|
          rfe->bailoutInfo->tryPC =
              UnwindEnvironmentToTryPc(frame.script(), tn);
          rfe->bailoutInfo->faultPC = frame.pc();
          return;
        }

        *hitBailoutException = true;
        MOZ_ASSERT(cx->isExceptionPending());
        break;
      }

      case TryNoteKind::ForOf:
      case TryNoteKind::Loop:
        break;

      // TryNoteKind::ForOfIterclose is handled internally by the try note
      // iterator.
      default:
        MOZ_CRASH("Unexpected try note");
    }
  }

  OnLeaveIonFrame(cx, frame, rfe);
}

static void OnLeaveBaselineFrame(JSContext* cx, const JSJitFrameIter& frame,
                                 jsbytecode* pc, ResumeFromException* rfe,
                                 bool frameOk) {
  BaselineFrame* baselineFrame = frame.baselineFrame();
  bool returnFromThisFrame = jit::DebugEpilogue(cx, baselineFrame, pc, frameOk);
  if (returnFromThisFrame) {
    rfe->kind = ExceptionResumeKind::ForcedReturnBaseline;
    rfe->framePointer = frame.fp();
    rfe->stackPointer = reinterpret_cast<uint8_t*>(baselineFrame);
  }
}

static inline void BaselineFrameAndStackPointersFromTryNote(
    const TryNote* tn, const JSJitFrameIter& frame, uint8_t** framePointer,
    uint8_t** stackPointer) {
  JSScript* script = frame.baselineFrame()->script();
  *framePointer = frame.fp();
  *stackPointer = *framePointer - BaselineFrame::Size() -
                  (script->nfixed() + tn->stackDepth) * sizeof(Value);
}

static void SettleOnTryNote(JSContext* cx, const TryNote* tn,
                            const JSJitFrameIter& frame, EnvironmentIter& ei,
                            ResumeFromException* rfe, jsbytecode** pc) {
  RootedScript script(cx, frame.baselineFrame()->script());

  // Unwind environment chain (pop block objects).
  if (cx->isExceptionPending()) {
    UnwindEnvironment(cx, ei, UnwindEnvironmentToTryPc(script, tn));
  }

  // Compute base pointer and stack pointer.
  BaselineFrameAndStackPointersFromTryNote(tn, frame, &rfe->framePointer,
                                           &rfe->stackPointer);

  // Compute the pc.
  *pc = script->offsetToPC(tn->start + tn->length);
}

class BaselineTryNoteFilter {
  const JSJitFrameIter& frame_;

 public:
  explicit BaselineTryNoteFilter(const JSJitFrameIter& frame) : frame_(frame) {}
  bool operator()(const TryNote* note) {
    BaselineFrame* frame = frame_.baselineFrame();

    uint32_t numValueSlots = frame_.baselineFrameNumValueSlots();
    MOZ_RELEASE_ASSERT(numValueSlots >= frame->script()->nfixed());

    uint32_t currDepth = numValueSlots - frame->script()->nfixed();
    return note->stackDepth <= currDepth;
  }
};

class TryNoteIterBaseline : public TryNoteIter<BaselineTryNoteFilter> {
 public:
  TryNoteIterBaseline(JSContext* cx, const JSJitFrameIter& frame,
                      jsbytecode* pc)
      : TryNoteIter(cx, frame.script(), pc, BaselineTryNoteFilter(frame)) {}
};

// Close all live iterators on a BaselineFrame due to exception unwinding. The
// pc parameter is updated to where the envs have been unwound to.
static void CloseLiveIteratorsBaselineForUncatchableException(
    JSContext* cx, const JSJitFrameIter& frame, jsbytecode* pc) {
  for (TryNoteIterBaseline tni(cx, frame, pc); !tni.done(); ++tni) {
    const TryNote* tn = *tni;
    switch (tn->kind()) {
      case TryNoteKind::ForIn: {
        uint8_t* framePointer;
        uint8_t* stackPointer;
        BaselineFrameAndStackPointersFromTryNote(tn, frame, &framePointer,
                                                 &stackPointer);
        Value iterValue(*(Value*)stackPointer);
        RootedObject iterObject(cx, &iterValue.toObject());
        UnwindIteratorForUncatchableException(iterObject);
        break;
      }

      default:
        break;
    }
  }
}

static bool ProcessTryNotesBaseline(JSContext* cx, const JSJitFrameIter& frame,
                                    EnvironmentIter& ei,
                                    ResumeFromException* rfe, jsbytecode** pc) {
  MOZ_ASSERT(frame.baselineFrame()->runningInInterpreter(),
             "Caller must ensure frame is an interpreter frame");

  RootedScript script(cx, frame.baselineFrame()->script());

  for (TryNoteIterBaseline tni(cx, frame, *pc); !tni.done(); ++tni) {
    const TryNote* tn = *tni;

    MOZ_ASSERT(cx->isExceptionPending());
    switch (tn->kind()) {
      case TryNoteKind::Catch: {
        // If we're closing a generator, we have to skip catch blocks.
        if (cx->isClosingGenerator()) {
          break;
        }

        SettleOnTryNote(cx, tn, frame, ei, rfe, pc);

        // Ion can compile try-catch, but bailing out to catch
        // exceptions is slow. Reset the warm-up counter so that if we
        // catch many exceptions we won't Ion-compile the script.
        script->resetWarmUpCounterToDelayIonCompilation();

        // Resume at the start of the catch block.
        frame.baselineFrame()->setInterpreterFields(*pc);
        rfe->kind = ExceptionResumeKind::Catch;
        if (IsBaselineInterpreterEnabled()) {
          const BaselineInterpreter& interp =
              cx->runtime()->jitRuntime()->baselineInterpreter();
          rfe->target = interp.interpretOpAddr().value;
        }
        return true;
      }

      case TryNoteKind::Finally: {
        SettleOnTryNote(cx, tn, frame, ei, rfe, pc);

        frame.baselineFrame()->setInterpreterFields(*pc);
        rfe->kind = ExceptionResumeKind::Finally;
        if (IsBaselineInterpreterEnabled()) {
          const BaselineInterpreter& interp =
              cx->runtime()->jitRuntime()->baselineInterpreter();
          rfe->target = interp.interpretOpAddr().value;
        }

        // Drop the exception instead of leaking cross compartment data.
        RootedValue exception(cx);
        RootedValue exceptionStack(cx);
        if (!cx->getPendingException(&exception) ||
            !cx->getPendingExceptionStack(&exceptionStack)) {
          rfe->exception = UndefinedValue();
          rfe->exceptionStack = NullValue();
        } else {
          rfe->exception = exception;
          rfe->exceptionStack = exceptionStack;
        }
        cx->clearPendingException();
        return true;
      }

      case TryNoteKind::ForIn: {
        uint8_t* framePointer;
        uint8_t* stackPointer;
        BaselineFrameAndStackPointersFromTryNote(tn, frame, &framePointer,
                                                 &stackPointer);
        Value iterValue(*reinterpret_cast<Value*>(stackPointer));
        JSObject* iterObject = &iterValue.toObject();
        CloseIterator(iterObject);
        break;
      }

      case TryNoteKind::Destructuring: {
        uint8_t* framePointer;
        uint8_t* stackPointer;
        BaselineFrameAndStackPointersFromTryNote(tn, frame, &framePointer,
                                                 &stackPointer);
        // Note: if this ever changes, also update the
        // TryNoteKind::Destructuring code in WarpBuilder.cpp!
        RootedValue doneValue(cx, *(reinterpret_cast<Value*>(stackPointer)));
        MOZ_RELEASE_ASSERT(!doneValue.isMagic());
        bool done = ToBoolean(doneValue);
        if (!done) {
          Value iterValue(*(reinterpret_cast<Value*>(stackPointer) + 1));
          RootedObject iterObject(cx, &iterValue.toObject());
          if (!IteratorCloseForException(cx, iterObject)) {
            SettleOnTryNote(cx, tn, frame, ei, rfe, pc);
            return false;
          }
        }
        break;
      }

      case TryNoteKind::ForOf:
      case TryNoteKind::Loop:
        break;

      // TryNoteKind::ForOfIterClose is handled internally by the try note
      // iterator.
      default:
        MOZ_CRASH("Invalid try note");
    }
  }
  return true;
}

static void HandleExceptionBaseline(JSContext* cx, JSJitFrameIter& frame,
                                    CommonFrameLayout* prevFrame,
                                    ResumeFromException* rfe) {
  MOZ_ASSERT(frame.isBaselineJS());
  MOZ_ASSERT(prevFrame);

  jsbytecode* pc;
  frame.baselineScriptAndPc(nullptr, &pc);

  // Ensure the BaselineFrame is an interpreter frame. This is easy to do and
  // simplifies the code below and interaction with DebugModeOSR.
  //
  // Note that we never return to this frame via the previous frame's return
  // address. We could set the return address to nullptr to ensure it's never
  // used, but the profiler expects a non-null return value for its JitCode map
  // lookup so we have to use an address in the interpreter code instead.
  if (!frame.baselineFrame()->runningInInterpreter()) {
    const BaselineInterpreter& interp =
        cx->runtime()->jitRuntime()->baselineInterpreter();
    uint8_t* retAddr = interp.codeRaw();
    BaselineFrame* baselineFrame = frame.baselineFrame();

    // Suppress profiler sampling while we fix up the frame to ensure the
    // sampler thread doesn't see an inconsistent state.
    AutoSuppressProfilerSampling suppressProfilerSampling(cx);
    baselineFrame->switchFromJitToInterpreterForExceptionHandler(cx, pc);
    prevFrame->setReturnAddress(retAddr);

    // Ensure the current iterator's resumePCInCurrentFrame_ isn't used
    // anywhere.
    frame.setResumePCInCurrentFrame(nullptr);
  }

  bool frameOk = false;
  RootedScript script(cx, frame.baselineFrame()->script());

  if (script->hasScriptCounts()) {
    PCCounts* counts = script->getThrowCounts(pc);
    // If we failed to allocate, then skip the increment and continue to
    // handle the exception.
    if (counts) {
      counts->numExec()++;
    }
  }

  bool hasTryNotes = !script->trynotes().empty();

again:
  if (cx->isExceptionPending()) {
    if (!cx->isClosingGenerator()) {
      if (!DebugAPI::onExceptionUnwind(cx, frame.baselineFrame())) {
        if (!cx->isExceptionPending()) {
          goto again;
        }
      }
      // Ensure that the debugger hasn't returned 'true' while clearing the
      // exception state.
      MOZ_ASSERT(cx->isExceptionPending());
    }

    if (hasTryNotes) {
      EnvironmentIter ei(cx, frame.baselineFrame(), pc);
      if (!ProcessTryNotesBaseline(cx, frame, ei, rfe, &pc)) {
        goto again;
      }
      if (rfe->kind != ExceptionResumeKind::EntryFrame) {
        // No need to increment the PCCounts number of execution here,
        // as the interpreter increments any PCCounts if present.
        MOZ_ASSERT_IF(script->hasScriptCounts(), script->maybeGetPCCounts(pc));
        return;
      }
    }

    frameOk = HandleClosingGeneratorReturn(cx, frame.baselineFrame(), frameOk);
  } else {
    if (hasTryNotes) {
      CloseLiveIteratorsBaselineForUncatchableException(cx, frame, pc);
    }

    // We may be propagating a forced return from a debugger hook function.
    if (MOZ_UNLIKELY(cx->isPropagatingForcedReturn())) {
      cx->clearPropagatingForcedReturn();
      frameOk = true;
    }
  }

  OnLeaveBaselineFrame(cx, frame, pc, rfe, frameOk);
}

static JitFrameLayout* GetLastProfilingFrame(ResumeFromException* rfe) {
  switch (rfe->kind) {
    case ExceptionResumeKind::EntryFrame:
    case ExceptionResumeKind::Wasm:
    case ExceptionResumeKind::WasmCatch:
      return nullptr;

    // The following all return into Baseline or Ion frames.
    case ExceptionResumeKind::Catch:
    case ExceptionResumeKind::Finally:
    case ExceptionResumeKind::ForcedReturnBaseline:
    case ExceptionResumeKind::ForcedReturnIon:
      return reinterpret_cast<JitFrameLayout*>(rfe->framePointer);

    // When resuming into a bailed-out ion frame, use the bailout info to
    // find the frame we are resuming into.
    case ExceptionResumeKind::Bailout:
      return reinterpret_cast<JitFrameLayout*>(rfe->bailoutInfo->incomingStack);
  }

  MOZ_CRASH("Invalid ResumeFromException type!");
  return nullptr;
}

void HandleExceptionWasm(JSContext* cx, wasm::WasmFrameIter* iter,
                         ResumeFromException* rfe) {
  MOZ_ASSERT(cx->activation()->asJit()->hasWasmExitFP());
  wasm::HandleThrow(cx, *iter, rfe);
  MOZ_ASSERT(iter->done());
}

void HandleException(ResumeFromException* rfe) {
  JSContext* cx = TlsContext.get();

#ifdef DEBUG
  if (!IsPortableBaselineInterpreterEnabled()) {
    cx->runtime()->jitRuntime()->clearDisallowArbitraryCode();
  }

  // Reset the counter when we bailed after MDebugEnterGCUnsafeRegion, but
  // before the matching MDebugLeaveGCUnsafeRegion.
  //
  // NOTE: EnterJit ensures the counter is zero when we enter JIT code.
  cx->resetInUnsafeRegion();
#endif

  auto resetProfilerFrame = mozilla::MakeScopeExit([=] {
    if (!IsPortableBaselineInterpreterEnabled()) {
      if (!cx->runtime()->jitRuntime()->isProfilerInstrumentationEnabled(
              cx->runtime())) {
        return;
      }
    }

    MOZ_ASSERT(cx->jitActivation == cx->profilingActivation());

    auto* lastProfilingFrame = GetLastProfilingFrame(rfe);
    cx->jitActivation->setLastProfilingFrame(lastProfilingFrame);
  });

  rfe->kind = ExceptionResumeKind::EntryFrame;

  JitSpew(JitSpew_IonInvalidate, "handling exception");

  JitActivation* activation = cx->activation()->asJit();

#ifdef CHECK_OSIPOINT_REGISTERS
  if (JitOptions.checkOsiPointRegisters) {
    activation->setCheckRegs(false);
  }
#endif

  JitFrameIter iter(cx->activation()->asJit(),
                    /* mustUnwindActivation = */ true);
  CommonFrameLayout* prevJitFrame = nullptr;
  while (!iter.done()) {
    if (iter.isWasm()) {
      prevJitFrame = nullptr;
      HandleExceptionWasm(cx, &iter.asWasm(), rfe);
      // If a wasm try-catch handler is found, we can immediately jump to it
      // and quit iterating through the stack.
      if (rfe->kind == ExceptionResumeKind::WasmCatch) {
        return;
      }
      if (!iter.done()) {
        ++iter;
      }
      continue;
    }

    JSJitFrameIter& frame = iter.asJSJit();

    // JIT code can enter same-compartment realms, so reset cx->realm to
    // this frame's realm.
    if (frame.isScripted()) {
      cx->setRealmForJitExceptionHandler(iter.realm());
    }

    if (frame.isIonJS()) {
      // Search each inlined frame for live iterator objects, and close
      // them.
      InlineFrameIterator frames(cx, &frame);

      // Invalidation state will be the same for all inlined scripts in the
      // frame.
      IonScript* ionScript = nullptr;
      bool invalidated = frame.checkInvalidation(&ionScript);

      // If we hit OOM or overrecursion while bailing out, we don't
      // attempt to bail out a second time for this Ion frame. Just unwind
      // and continue at the next frame.
      bool hitBailoutException = false;
      for (;;) {
        HandleExceptionIon(cx, frames, rfe, &hitBailoutException);

        if (rfe->kind == ExceptionResumeKind::Bailout ||
            rfe->kind == ExceptionResumeKind::ForcedReturnIon) {
          if (invalidated) {
            ionScript->decrementInvalidationCount(cx->gcContext());
          }
          return;
        }

        MOZ_ASSERT(rfe->kind == ExceptionResumeKind::EntryFrame);

        // When profiling, each frame popped needs a notification that
        // the function has exited, so invoke the probe that a function
        // is exiting.

        JSScript* script = frames.script();
        probes::ExitScript(cx, script, script->function(),
                           /* popProfilerFrame = */ false);
        if (!frames.more()) {
          break;
        }
        ++frames;
      }

      // Remove left-over state which might have been needed for bailout.
      activation->removeIonFrameRecovery(frame.jsFrame());
      activation->removeRematerializedFrame(frame.fp());

      // If invalidated, decrement the number of frames remaining on the
      // stack for the given IonScript.
      if (invalidated) {
        ionScript->decrementInvalidationCount(cx->gcContext());
      }

    } else if (frame.isBaselineJS()) {
      HandleExceptionBaseline(cx, frame, prevJitFrame, rfe);

      if (rfe->kind != ExceptionResumeKind::EntryFrame &&
          rfe->kind != ExceptionResumeKind::ForcedReturnBaseline) {
        return;
      }

      // Unwind profiler pseudo-stack
      JSScript* script = frame.script();
      probes::ExitScript(cx, script, script->function(),
                         /* popProfilerFrame = */ false);

      if (rfe->kind == ExceptionResumeKind::ForcedReturnBaseline) {
        return;
      }
    }

    prevJitFrame = frame.current();
    ++iter;
  }

  // Wasm sets its own value of SP in HandleExceptionWasm.
  if (iter.isJSJit()) {
    MOZ_ASSERT(rfe->kind == ExceptionResumeKind::EntryFrame);
    rfe->framePointer = iter.asJSJit().current()->callerFramePtr();
    rfe->stackPointer =
        iter.asJSJit().fp() + CommonFrameLayout::offsetOfReturnAddress();
  }
}

// Turns a JitFrameLayout into an UnwoundJit ExitFrameLayout.
void EnsureUnwoundJitExitFrame(JitActivation* act, JitFrameLayout* frame) {
  ExitFrameLayout* exitFrame = reinterpret_cast<ExitFrameLayout*>(frame);

  if (act->jsExitFP() == (uint8_t*)frame) {
    // If we already called this function for the current frame, do
    // nothing.
    MOZ_ASSERT(exitFrame->isUnwoundJitExit());
    return;
  }

#ifdef DEBUG
  JSJitFrameIter iter(act);
  while (!iter.isScripted()) {
    ++iter;
  }
  MOZ_ASSERT(iter.current() == frame, "|frame| must be the top JS frame");

  MOZ_ASSERT(!!act->jsExitFP());
  MOZ_ASSERT((uint8_t*)exitFrame->footer() >= act->jsExitFP(),
             "Must have space for ExitFooterFrame before jsExitFP");
#endif

  act->setJSExitFP((uint8_t*)frame);
  exitFrame->footer()->setUnwoundJitExitFrame();
  MOZ_ASSERT(exitFrame->isUnwoundJitExit());
}

JSScript* MaybeForwardedScriptFromCalleeToken(CalleeToken token) {
  switch (GetCalleeTokenTag(token)) {
    case CalleeToken_Script:
      return MaybeForwarded(CalleeTokenToScript(token));
    case CalleeToken_Function:
    case CalleeToken_FunctionConstructing: {
      JSFunction* fun = MaybeForwarded(CalleeTokenToFunction(token));
      return MaybeForwarded(fun)->nonLazyScript();
    }
  }
  MOZ_CRASH("invalid callee token tag");
}

CalleeToken TraceCalleeToken(JSTracer* trc, CalleeToken token) {
  switch (CalleeTokenTag tag = GetCalleeTokenTag(token)) {
    case CalleeToken_Function:
    case CalleeToken_FunctionConstructing: {
      JSFunction* fun = CalleeTokenToFunction(token);
      TraceRoot(trc, &fun, "jit-callee");
      return CalleeToToken(fun, tag == CalleeToken_FunctionConstructing);
    }
    case CalleeToken_Script: {
      JSScript* script = CalleeTokenToScript(token);
      TraceRoot(trc, &script, "jit-script");
      return CalleeToToken(script);
    }
    default:
      MOZ_CRASH("unknown callee token type");
  }
}

uintptr_t* JitFrameLayout::slotRef(SafepointSlotEntry where) {
  if (where.stack) {
    return (uintptr_t*)((uint8_t*)this - where.slot);
  }
  return (uintptr_t*)((uint8_t*)thisAndActualArgs() + where.slot);
}

#ifdef DEBUG
void ExitFooterFrame::assertValidVMFunctionId() const {
  MOZ_ASSERT(data_ >= uintptr_t(ExitFrameType::VMFunction));
  MOZ_ASSERT(data_ - uintptr_t(ExitFrameType::VMFunction) < NumVMFunctions());
}
#endif

#ifdef JS_NUNBOX32
static inline uintptr_t ReadAllocation(const JSJitFrameIter& frame,
                                       const LAllocation* a) {
  if (a->isGeneralReg()) {
    Register reg = a->toGeneralReg()->reg();
    return frame.machineState().read(reg);
  }
  return *frame.jsFrame()->slotRef(SafepointSlotEntry(a));
}
#endif

static void TraceThisAndArguments(JSTracer* trc, const JSJitFrameIter& frame,
                                  JitFrameLayout* layout) {
  // Trace |this| and any extra actual arguments for an Ion frame. Tracing
  // of formal arguments is taken care of by the frame's safepoint/snapshot,
  // except when the script might have lazy arguments or rest, in which case
  // we trace them as well. We also have to trace formals if we have a
  // LazyLink frame or an InterpreterStub frame or a special JSJit to wasm
  // frame (since wasm doesn't use snapshots).

  if (!CalleeTokenIsFunction(layout->calleeToken())) {
    return;
  }

  JSFunction* fun = CalleeTokenToFunction(layout->calleeToken());

  size_t numFormals = fun->nargs();
  size_t numArgs = std::max(layout->numActualArgs(), numFormals);
  size_t firstArg = 0;

  if (frame.type() != FrameType::JSJitToWasm &&
      !frame.isExitFrameLayout<CalledFromJitExitFrameLayout>() &&
      !fun->nonLazyScript()->mayReadFrameArgsDirectly()) {
    firstArg = numFormals;
  }

  Value* argv = layout->thisAndActualArgs();

  // Trace |this|.
  TraceRoot(trc, argv, "ion-thisv");

  // Trace arguments. Note + 1 for thisv.
  for (size_t i = firstArg; i < numArgs; i++) {
    TraceRoot(trc, &argv[i + 1], "ion-argv");
  }

  // Always trace the new.target from the frame. It's not in the snapshots.
  // +1 to pass |this|
  if (CalleeTokenIsConstructing(layout->calleeToken())) {
    TraceRoot(trc, &argv[1 + numArgs], "ion-newTarget");
  }
}

#ifdef JS_NUNBOX32
static inline void WriteAllocation(const JSJitFrameIter& frame,
                                   const LAllocation* a, uintptr_t value) {
  if (a->isGeneralReg()) {
    Register reg = a->toGeneralReg()->reg();
    frame.machineState().write(reg, value);
  } else {
    *frame.jsFrame()->slotRef(SafepointSlotEntry(a)) = value;
  }
}
#endif

static void TraceIonJSFrame(JSTracer* trc, const JSJitFrameIter& frame) {
  JitFrameLayout* layout = (JitFrameLayout*)frame.fp();

  layout->replaceCalleeToken(TraceCalleeToken(trc, layout->calleeToken()));

  IonScript* ionScript = nullptr;
  if (frame.checkInvalidation(&ionScript)) {
    // This frame has been invalidated, meaning that its IonScript is no
    // longer reachable through the callee token (JSFunction/JSScript->ion
    // is now nullptr or recompiled). Manually trace it here.
    ionScript->trace(trc);
  } else {
    ionScript = frame.ionScriptFromCalleeToken();
  }

  TraceThisAndArguments(trc, frame, frame.jsFrame());

  const SafepointIndex* si =
      ionScript->getSafepointIndex(frame.resumePCinCurrentFrame());

  SafepointReader safepoint(ionScript, si);

  // Scan through slots which contain pointers (or on punboxing systems,
  // actual values).
  SafepointSlotEntry entry;

  while (safepoint.getGcSlot(&entry)) {
    uintptr_t* ref = layout->slotRef(entry);
    TraceGenericPointerRoot(trc, reinterpret_cast<gc::Cell**>(ref),
                            "ion-gc-slot");
  }

  uintptr_t* spill = frame.spillBase();
  LiveGeneralRegisterSet gcRegs = safepoint.gcSpills();
  LiveGeneralRegisterSet valueRegs = safepoint.valueSpills();
  LiveGeneralRegisterSet wasmAnyRefRegs = safepoint.wasmAnyRefSpills();
  for (GeneralRegisterBackwardIterator iter(safepoint.allGprSpills());
       iter.more(); ++iter) {
    --spill;
    if (gcRegs.has(*iter)) {
      TraceGenericPointerRoot(trc, reinterpret_cast<gc::Cell**>(spill),
                              "ion-gc-spill");
    } else if (valueRegs.has(*iter)) {
      TraceRoot(trc, reinterpret_cast<Value*>(spill), "ion-value-spill");
    } else if (wasmAnyRefRegs.has(*iter)) {
      TraceRoot(trc, reinterpret_cast<wasm::AnyRef*>(spill),
                "ion-anyref-spill");
    }
  }

#ifdef JS_PUNBOX64
  while (safepoint.getValueSlot(&entry)) {
    Value* v = (Value*)layout->slotRef(entry);
    TraceRoot(trc, v, "ion-gc-slot");
  }
#else
  LAllocation type, payload;
  while (safepoint.getNunboxSlot(&type, &payload)) {
    JSValueTag tag = JSValueTag(ReadAllocation(frame, &type));
    uintptr_t rawPayload = ReadAllocation(frame, &payload);

    Value v = Value::fromTagAndPayload(tag, rawPayload);
    TraceRoot(trc, &v, "ion-torn-value");

    if (v != Value::fromTagAndPayload(tag, rawPayload)) {
      // GC moved the value, replace the stored payload.
      rawPayload = v.toNunboxPayload();
      WriteAllocation(frame, &payload, rawPayload);
    }
  }
#endif

  // Skip over slots/elements to get to wasm anyrefs
  while (safepoint.getSlotsOrElementsSlot(&entry)) {
  }

  while (safepoint.getWasmAnyRefSlot(&entry)) {
    wasm::AnyRef* v = (wasm::AnyRef*)layout->slotRef(entry);
    TraceRoot(trc, v, "ion-wasm-anyref-slot");
  }
}

static void TraceBailoutFrame(JSTracer* trc, const JSJitFrameIter& frame) {
  JitFrameLayout* layout = (JitFrameLayout*)frame.fp();

  layout->replaceCalleeToken(TraceCalleeToken(trc, layout->calleeToken()));

  // We have to trace the list of actual arguments, as only formal arguments
  // are represented in the Snapshot.
  TraceThisAndArguments(trc, frame, frame.jsFrame());

  // Under a bailout, do not have a Safepoint to only iterate over GC-things.
  // Thus we use a SnapshotIterator to trace all the locations which would be
  // used to reconstruct the Baseline frame.
  //
  // Note that at the time where this function is called, we have not yet
  // started to reconstruct baseline frames.

  // The vector of recover instructions is already traced as part of the
  // JitActivation.
  SnapshotIterator snapIter(frame,
                            frame.activation()->bailoutData()->machineState());

  // For each instruction, we read the allocations without evaluating the
  // recover instruction, nor reconstructing the frame. We are only looking at
  // tracing readable allocations.
  while (true) {
    while (snapIter.moreAllocations()) {
      snapIter.traceAllocation(trc);
    }

    if (!snapIter.moreInstructions()) {
      break;
    }
    snapIter.nextInstruction();
  }
}

static void UpdateIonJSFrameForMinorGC(JSRuntime* rt,
                                       const JSJitFrameIter& frame) {
  // Minor GCs may move slots/elements allocated in the nursery. Update
  // any slots/elements pointers stored in this frame.

  JitFrameLayout* layout = (JitFrameLayout*)frame.fp();

  IonScript* ionScript = nullptr;
  if (frame.checkInvalidation(&ionScript)) {
    // This frame has been invalidated, meaning that its IonScript is no
    // longer reachable through the callee token (JSFunction/JSScript->ion
    // is now nullptr or recompiled).
  } else {
    ionScript = frame.ionScriptFromCalleeToken();
  }

  Nursery& nursery = rt->gc.nursery();

  const SafepointIndex* si =
      ionScript->getSafepointIndex(frame.resumePCinCurrentFrame());
  SafepointReader safepoint(ionScript, si);

  LiveGeneralRegisterSet slotsRegs = safepoint.slotsOrElementsSpills();
  uintptr_t* spill = frame.spillBase();
  for (GeneralRegisterBackwardIterator iter(safepoint.allGprSpills());
       iter.more(); ++iter) {
    --spill;
    if (slotsRegs.has(*iter)) {
      nursery.forwardBufferPointer(spill);
    }
  }

  // Skip to the right place in the safepoint
  SafepointSlotEntry entry;
  while (safepoint.getGcSlot(&entry)) {
  }

#ifdef JS_PUNBOX64
  while (safepoint.getValueSlot(&entry)) {
  }
#else
  LAllocation type, payload;
  while (safepoint.getNunboxSlot(&type, &payload)) {
  }
#endif

  while (safepoint.getSlotsOrElementsSlot(&entry)) {
    nursery.forwardBufferPointer(layout->slotRef(entry));
  }
}

static void TraceBaselineStubFrame(JSTracer* trc, const JSJitFrameIter& frame) {
  // Trace the ICStub pointer stored in the stub frame. This is necessary
  // so that we don't destroy the stub code after unlinking the stub.

  MOZ_ASSERT(frame.type() == FrameType::BaselineStub);
  BaselineStubFrameLayout* layout = (BaselineStubFrameLayout*)frame.fp();

  if (ICStub* stub = layout->maybeStubPtr()) {
    if (stub->isFallback()) {
      // Fallback stubs use runtime-wide trampoline code we don't need to trace.
      MOZ_ASSERT(stub->usesTrampolineCode());
    } else {
      MOZ_ASSERT(stub->toCacheIRStub()->makesGCCalls());
      stub->toCacheIRStub()->trace(trc);

#ifndef ENABLE_PORTABLE_BASELINE_INTERP
      for (int i = 0; i < stub->jitCode()->localTracingSlots(); ++i) {
        TraceRoot(trc, layout->locallyTracedValuePtr(i),
                  "baseline-local-tracing-slot");
      }
#endif
    }
  }
}

static void TraceWeakBaselineStubFrame(JSTracer* trc,
                                       const JSJitFrameIter& frame) {
  MOZ_ASSERT(frame.type() == FrameType::BaselineStub);
  BaselineStubFrameLayout* layout = (BaselineStubFrameLayout*)frame.fp();

  if (ICStub* stub = layout->maybeStubPtr()) {
    if (!stub->isFallback()) {
      MOZ_ASSERT(stub->toCacheIRStub()->makesGCCalls());
      stub->toCacheIRStub()->traceWeak(trc);
    }
  }
}

static void TraceIonICCallFrame(JSTracer* trc, const JSJitFrameIter& frame) {
  MOZ_ASSERT(frame.type() == FrameType::IonICCall);
  IonICCallFrameLayout* layout = (IonICCallFrameLayout*)frame.fp();
  TraceRoot(trc, layout->stubCode(), "ion-ic-call-code");

  for (int i = 0; i < (*layout->stubCode())->localTracingSlots(); ++i) {
    TraceRoot(trc, layout->locallyTracedValuePtr(i),
              "ion-ic-local-tracing-slot");
  }
}

#if defined(JS_CODEGEN_ARM64) || defined(JS_CODEGEN_MIPS32)
uint8_t* alignDoubleSpill(uint8_t* pointer) {
  uintptr_t address = reinterpret_cast<uintptr_t>(pointer);
  address &= ~(uintptr_t(ABIStackAlignment) - 1);
  return reinterpret_cast<uint8_t*>(address);
}
#endif

#ifdef JS_CODEGEN_MIPS32
static void TraceJitExitFrameCopiedArguments(JSTracer* trc,
                                             const VMFunctionData* f,
                                             ExitFooterFrame* footer) {
  uint8_t* doubleArgs = footer->alignedForABI();
  if (f->outParam == Type_Handle) {
    doubleArgs -= sizeof(Value);
  }
  doubleArgs -= f->doubleByRefArgs() * sizeof(double);

  for (uint32_t explicitArg = 0; explicitArg < f->explicitArgs; explicitArg++) {
    if (f->argProperties(explicitArg) == VMFunctionData::DoubleByRef) {
      // Arguments with double size can only have RootValue type.
      if (f->argRootType(explicitArg) == VMFunctionData::RootValue) {
        TraceRoot(trc, reinterpret_cast<Value*>(doubleArgs), "ion-vm-args");
      } else {
        MOZ_ASSERT(f->argRootType(explicitArg) == VMFunctionData::RootNone);
      }
      doubleArgs += sizeof(double);
    }
  }
}
#else
static void TraceJitExitFrameCopiedArguments(JSTracer* trc,
                                             const VMFunctionData* f,
                                             ExitFooterFrame* footer) {
  // This is NO-OP on other platforms.
}
#endif

static void TraceJitExitFrame(JSTracer* trc, const JSJitFrameIter& frame) {
  ExitFooterFrame* footer = frame.exitFrame()->footer();

  // This corresponds to the case where we have build a fake exit frame which
  // handles the case of a native function call. We need to trace the argument
  // vector of the function call, and also new.target if it was a constructing
  // call.
  if (frame.isExitFrameLayout<NativeExitFrameLayout>()) {
    NativeExitFrameLayout* native =
        frame.exitFrame()->as<NativeExitFrameLayout>();
    size_t len = native->argc() + 2;
    Value* vp = native->vp();
    TraceRootRange(trc, len, vp, "ion-native-args");
    if (frame.isExitFrameLayout<ConstructNativeExitFrameLayout>()) {
      TraceRoot(trc, vp + len, "ion-native-new-target");
    }
    return;
  }

  if (frame.isExitFrameLayout<IonOOLNativeExitFrameLayout>()) {
    IonOOLNativeExitFrameLayout* oolnative =
        frame.exitFrame()->as<IonOOLNativeExitFrameLayout>();
    TraceRoot(trc, oolnative->stubCode(), "ion-ool-native-code");
    TraceRoot(trc, oolnative->vp(), "iol-ool-native-vp");
    size_t len = oolnative->argc() + 1;
    TraceRootRange(trc, len, oolnative->thisp(), "ion-ool-native-thisargs");
    return;
  }

  if (frame.isExitFrameLayout<IonOOLProxyExitFrameLayout>()) {
    IonOOLProxyExitFrameLayout* oolproxy =
        frame.exitFrame()->as<IonOOLProxyExitFrameLayout>();
    TraceRoot(trc, oolproxy->stubCode(), "ion-ool-proxy-code");
    TraceRoot(trc, oolproxy->vp(), "ion-ool-proxy-vp");
    TraceRoot(trc, oolproxy->id(), "ion-ool-proxy-id");
    TraceRoot(trc, oolproxy->proxy(), "ion-ool-proxy-proxy");
    return;
  }

  if (frame.isExitFrameLayout<IonDOMExitFrameLayout>()) {
    IonDOMExitFrameLayout* dom = frame.exitFrame()->as<IonDOMExitFrameLayout>();
    TraceRoot(trc, dom->thisObjAddress(), "ion-dom-args");
    if (dom->isMethodFrame()) {
      IonDOMMethodExitFrameLayout* method =
          reinterpret_cast<IonDOMMethodExitFrameLayout*>(dom);
      size_t len = method->argc() + 2;
      Value* vp = method->vp();
      TraceRootRange(trc, len, vp, "ion-dom-args");
    } else {
      TraceRoot(trc, dom->vp(), "ion-dom-args");
    }
    return;
  }

  if (frame.isExitFrameLayout<CalledFromJitExitFrameLayout>()) {
    auto* layout = frame.exitFrame()->as<CalledFromJitExitFrameLayout>();
    JitFrameLayout* jsLayout = layout->jsFrame();
    jsLayout->replaceCalleeToken(
        TraceCalleeToken(trc, jsLayout->calleeToken()));
    TraceThisAndArguments(trc, frame, jsLayout);
    return;
  }

  if (frame.isExitFrameLayout<DirectWasmJitCallFrameLayout>()) {
    // Nothing needs to be traced here at the moment -- the arguments to the
    // callee are traced by the callee, and the inlined caller does not push
    // anything else.
    return;
  }

  if (frame.isBareExit() || frame.isUnwoundJitExit()) {
    // Nothing to trace. Fake exit frame pushed for VM functions with
    // nothing to trace on the stack or unwound JitFrameLayout.
    return;
  }

  MOZ_ASSERT(frame.exitFrame()->isWrapperExit());

  const VMFunctionData& f = GetVMFunction(footer->functionId());

  // Trace arguments of the VM wrapper.
  uint8_t* argBase = frame.exitFrame()->argBase();
  for (uint32_t explicitArg = 0; explicitArg < f.explicitArgs; explicitArg++) {
    switch (f.argRootType(explicitArg)) {
      case VMFunctionData::RootNone:
        break;
      case VMFunctionData::RootObject: {
        // Sometimes we can bake in HandleObjects to nullptr.
        JSObject** pobj = reinterpret_cast<JSObject**>(argBase);
        if (*pobj) {
          TraceRoot(trc, pobj, "ion-vm-args");
        }
        break;
      }
      case VMFunctionData::RootString:
        TraceRoot(trc, reinterpret_cast<JSString**>(argBase), "ion-vm-args");
        break;
      case VMFunctionData::RootValue:
        TraceRoot(trc, reinterpret_cast<Value*>(argBase), "ion-vm-args");
        break;
      case VMFunctionData::RootId:
        TraceRoot(trc, reinterpret_cast<jsid*>(argBase), "ion-vm-args");
        break;
      case VMFunctionData::RootCell:
        TraceGenericPointerRoot(trc, reinterpret_cast<gc::Cell**>(argBase),
                                "ion-vm-args");
        break;
      case VMFunctionData::RootBigInt:
        TraceRoot(trc, reinterpret_cast<JS::BigInt**>(argBase), "ion-vm-args");
        break;
    }

    switch (f.argProperties(explicitArg)) {
      case VMFunctionData::WordByValue:
      case VMFunctionData::WordByRef:
        argBase += sizeof(void*);
        break;
      case VMFunctionData::DoubleByValue:
      case VMFunctionData::DoubleByRef:
        argBase += 2 * sizeof(void*);
        break;
    }
  }

  if (f.outParam == Type_Handle) {
    switch (f.outParamRootType) {
      case VMFunctionData::RootNone:
        MOZ_CRASH("Handle outparam must have root type");
      case VMFunctionData::RootObject:
        TraceRoot(trc, footer->outParam<JSObject*>(), "ion-vm-out");
        break;
      case VMFunctionData::RootString:
        TraceRoot(trc, footer->outParam<JSString*>(), "ion-vm-out");
        break;
      case VMFunctionData::RootValue:
        TraceRoot(trc, footer->outParam<Value>(), "ion-vm-outvp");
        break;
      case VMFunctionData::RootId:
        TraceRoot(trc, footer->outParam<jsid>(), "ion-vm-outvp");
        break;
      case VMFunctionData::RootCell:
        TraceGenericPointerRoot(trc, footer->outParam<gc::Cell*>(),
                                "ion-vm-out");
        break;
      case VMFunctionData::RootBigInt:
        TraceRoot(trc, footer->outParam<JS::BigInt*>(), "ion-vm-out");
        break;
    }
  }

  TraceJitExitFrameCopiedArguments(trc, &f, footer);
}

static void TraceBaselineInterpreterEntryFrame(JSTracer* trc,
                                               const JSJitFrameIter& frame) {
  // Baseline Interpreter entry code generated under --emit-interpreter-entry.
  BaselineInterpreterEntryFrameLayout* layout =
      (BaselineInterpreterEntryFrameLayout*)frame.fp();
  layout->replaceCalleeToken(TraceCalleeToken(trc, layout->calleeToken()));
  TraceThisAndArguments(trc, frame, layout);
}

static void TraceRectifierFrame(JSTracer* trc, const JSJitFrameIter& frame) {
  // Trace thisv.
  //
  // Baseline JIT code generated as part of the ICCall_Fallback stub may use
  // it if we're calling a constructor that returns a primitive value.
  RectifierFrameLayout* layout = (RectifierFrameLayout*)frame.fp();
  TraceRoot(trc, &layout->thisv(), "rectifier-thisv");
}

static void TraceJSJitToWasmFrame(JSTracer* trc, const JSJitFrameIter& frame) {
  // This is doing a subset of TraceIonJSFrame, since the callee doesn't
  // have a script.
  JitFrameLayout* layout = (JitFrameLayout*)frame.fp();
  layout->replaceCalleeToken(TraceCalleeToken(trc, layout->calleeToken()));
  TraceThisAndArguments(trc, frame, layout);
}

static void TraceJitActivation(JSTracer* trc, JitActivation* activation) {
#ifdef CHECK_OSIPOINT_REGISTERS
  if (JitOptions.checkOsiPointRegisters) {
    // GC can modify spilled registers, breaking our register checks.
    // To handle this, we disable these checks for the current VM call
    // when a GC happens.
    activation->setCheckRegs(false);
  }
#endif

  activation->traceRematerializedFrames(trc);
  activation->traceIonRecovery(trc);

  // This is used for sanity checking continuity of the sequence of wasm stack
  // maps as we unwind.  It has no functional purpose.
  uintptr_t highestByteVisitedInPrevWasmFrame = 0;

  for (JitFrameIter frames(activation); !frames.done(); ++frames) {
    if (frames.isJSJit()) {
      const JSJitFrameIter& jitFrame = frames.asJSJit();
      switch (jitFrame.type()) {
        case FrameType::Exit:
          TraceJitExitFrame(trc, jitFrame);
          break;
        case FrameType::BaselineJS:
          jitFrame.baselineFrame()->trace(trc, jitFrame);
          break;
        case FrameType::IonJS:
          TraceIonJSFrame(trc, jitFrame);
          break;
        case FrameType::BaselineStub:
          TraceBaselineStubFrame(trc, jitFrame);
          break;
        case FrameType::Bailout:
          TraceBailoutFrame(trc, jitFrame);
          break;
        case FrameType::BaselineInterpreterEntry:
          TraceBaselineInterpreterEntryFrame(trc, jitFrame);
          break;
        case FrameType::Rectifier:
          TraceRectifierFrame(trc, jitFrame);
          break;
        case FrameType::IonICCall:
          TraceIonICCallFrame(trc, jitFrame);
          break;
        case FrameType::WasmToJSJit:
          // Ignore: this is a special marker used to let the
          // JitFrameIter know the frame above is a wasm frame, handled
          // in the next iteration.
          break;
        case FrameType::JSJitToWasm:
          TraceJSJitToWasmFrame(trc, jitFrame);
          break;
        default:
          MOZ_CRASH("unexpected frame type");
      }
      highestByteVisitedInPrevWasmFrame = 0; /* "unknown" */
    } else {
      MOZ_ASSERT(frames.isWasm());
      uint8_t* nextPC = frames.resumePCinCurrentFrame();
      MOZ_ASSERT(nextPC != 0);
      wasm::WasmFrameIter& wasmFrameIter = frames.asWasm();
      wasm::Instance* instance = wasmFrameIter.instance();
      wasm::TraceInstanceEdge(trc, instance, "WasmFrameIter instance");
      highestByteVisitedInPrevWasmFrame = instance->traceFrame(
          trc, wasmFrameIter, nextPC, highestByteVisitedInPrevWasmFrame);
    }
  }
}

void TraceJitActivations(JSContext* cx, JSTracer* trc) {
  for (JitActivationIterator activations(cx); !activations.done();
       ++activations) {
    TraceJitActivation(trc, activations->asJit());
  }
}

void TraceWeakJitActivationsInSweepingZones(JSContext* cx, JSTracer* trc) {
  for (JitActivationIterator activation(cx); !activation.done(); ++activation) {
    if (activation->compartment()->zone()->isGCSweeping()) {
      for (JitFrameIter frame(activation->asJit()); !frame.done(); ++frame) {
        if (frame.isJSJit()) {
          const JSJitFrameIter& jitFrame = frame.asJSJit();
          if (jitFrame.type() == FrameType::BaselineStub) {
            TraceWeakBaselineStubFrame(trc, jitFrame);
          }
        }
      }
    }
  }
}

void UpdateJitActivationsForMinorGC(JSRuntime* rt) {
  MOZ_ASSERT(JS::RuntimeHeapIsMinorCollecting());
  JSContext* cx = rt->mainContextFromOwnThread();
  for (JitActivationIterator activations(cx); !activations.done();
       ++activations) {
    for (JitFrameIter iter(activations->asJit()); !iter.done(); ++iter) {
      if (iter.isJSJit()) {
        const JSJitFrameIter& jitFrame = iter.asJSJit();
        if (jitFrame.type() == FrameType::IonJS) {
          UpdateIonJSFrameForMinorGC(rt, jitFrame);
        }
      } else if (iter.isWasm()) {
        const wasm::WasmFrameIter& frame = iter.asWasm();
        frame.instance()->updateFrameForMovingGC(
            frame, frame.resumePCinCurrentFrame());
      }
    }
  }
}

void UpdateJitActivationsForCompactingGC(JSRuntime* rt) {
  MOZ_ASSERT(JS::RuntimeHeapIsMajorCollecting());
  JSContext* cx = rt->mainContextFromOwnThread();
  for (JitActivationIterator activations(cx); !activations.done();
       ++activations) {
    for (JitFrameIter iter(activations->asJit()); !iter.done(); ++iter) {
      if (iter.isWasm()) {
        const wasm::WasmFrameIter& frame = iter.asWasm();
        frame.instance()->updateFrameForMovingGC(
            frame, frame.resumePCinCurrentFrame());
      }
    }
  }
}

JSScript* GetTopJitJSScript(JSContext* cx) {
  JSJitFrameIter frame(cx->activation()->asJit());
  MOZ_ASSERT(frame.type() == FrameType::Exit);
  ++frame;

  if (frame.isBaselineStub()) {
    ++frame;
    MOZ_ASSERT(frame.isBaselineJS());
  }

  MOZ_ASSERT(frame.isScripted());
  return frame.script();
}

RInstructionResults::RInstructionResults(JitFrameLayout* fp)
    : results_(nullptr), fp_(fp), initialized_(false) {}

RInstructionResults::RInstructionResults(RInstructionResults&& src)
    : results_(std::move(src.results_)),
      fp_(src.fp_),
      initialized_(src.initialized_) {
  src.initialized_ = false;
}

RInstructionResults& RInstructionResults::operator=(RInstructionResults&& rhs) {
  MOZ_ASSERT(&rhs != this, "self-moves are prohibited");
  this->~RInstructionResults();
  new (this) RInstructionResults(std::move(rhs));
  return *this;
}

RInstructionResults::~RInstructionResults() {
  // results_ is freed by the UniquePtr.
}

bool RInstructionResults::init(JSContext* cx, uint32_t numResults) {
  if (numResults) {
    results_ = cx->make_unique<Values>();
    if (!results_) {
      return false;
    }
    if (!results_->growBy(numResults)) {
      ReportOutOfMemory(cx);
      return false;
    }

    Value guard = MagicValue(JS_ION_BAILOUT);
    for (size_t i = 0; i < numResults; i++) {
      (*results_)[i].init(guard);
    }
  }

  initialized_ = true;
  return true;
}

bool RInstructionResults::isInitialized() const { return initialized_; }

size_t RInstructionResults::length() const { return results_->length(); }

JitFrameLayout* RInstructionResults::frame() const {
  MOZ_ASSERT(fp_);
  return fp_;
}

HeapPtr<Value>& RInstructionResults::operator[](size_t index) {
  return (*results_)[index];
}

void RInstructionResults::trace(JSTracer* trc) {
  // Note: The vector necessary exists, otherwise this object would not have
  // been stored on the activation from where the trace function is called.
  TraceRange(trc, results_->length(), results_->begin(), "ion-recover-results");
}

SnapshotIterator::SnapshotIterator(const JSJitFrameIter& iter,
                                   const MachineState* machineState)
    : snapshot_(iter.ionScript()->snapshots(), iter.snapshotOffset(),
                iter.ionScript()->snapshotsRVATableSize(),
                iter.ionScript()->snapshotsListSize()),
      recover_(snapshot_, iter.ionScript()->recovers(),
               iter.ionScript()->recoversSize()),
      fp_(iter.jsFrame()),
      machine_(machineState),
      ionScript_(iter.ionScript()),
      instructionResults_(nullptr) {}

SnapshotIterator::SnapshotIterator()
    : snapshot_(nullptr, 0, 0, 0),
      recover_(snapshot_, nullptr, 0),
      fp_(nullptr),
      machine_(nullptr),
      ionScript_(nullptr),
      instructionResults_(nullptr) {}

uintptr_t SnapshotIterator::fromStack(int32_t offset) const {
  return ReadFrameSlot(fp_, offset);
}

static Value FromObjectPayload(uintptr_t payload) {
  MOZ_ASSERT(payload != 0);
  return ObjectValue(*reinterpret_cast<JSObject*>(payload));
}

static Value FromStringPayload(uintptr_t payload) {
  return StringValue(reinterpret_cast<JSString*>(payload));
}

static Value FromSymbolPayload(uintptr_t payload) {
  return SymbolValue(reinterpret_cast<JS::Symbol*>(payload));
}

static Value FromBigIntPayload(uintptr_t payload) {
  return BigIntValue(reinterpret_cast<JS::BigInt*>(payload));
}

static Value FromTypedPayload(JSValueType type, uintptr_t payload) {
  switch (type) {
    case JSVAL_TYPE_INT32:
      return Int32Value(payload);
    case JSVAL_TYPE_BOOLEAN:
      return BooleanValue(!!payload);
    case JSVAL_TYPE_STRING:
      return FromStringPayload(payload);
    case JSVAL_TYPE_SYMBOL:
      return FromSymbolPayload(payload);
    case JSVAL_TYPE_BIGINT:
      return FromBigIntPayload(payload);
    case JSVAL_TYPE_OBJECT:
      return FromObjectPayload(payload);
    default:
      MOZ_CRASH("unexpected type - needs payload");
  }
}

bool SnapshotIterator::allocationReadable(const RValueAllocation& alloc,
                                          ReadMethod rm) {
  // If we have to recover stores, and if we are not interested in the
  // default value of the instruction, then we have to check if the recover
  // instruction results are available.
  if (alloc.needSideEffect() && rm != ReadMethod::AlwaysDefault) {
    if (!hasInstructionResults()) {
      return false;
    }
  }

  switch (alloc.mode()) {
    case RValueAllocation::DOUBLE_REG:
      return hasRegister(alloc.fpuReg());

    case RValueAllocation::TYPED_REG:
      return hasRegister(alloc.reg2());

#if defined(JS_NUNBOX32)
    case RValueAllocation::UNTYPED_REG_REG:
      return hasRegister(alloc.reg()) && hasRegister(alloc.reg2());
    case RValueAllocation::UNTYPED_REG_STACK:
      return hasRegister(alloc.reg()) && hasStack(alloc.stackOffset2());
    case RValueAllocation::UNTYPED_STACK_REG:
      return hasStack(alloc.stackOffset()) && hasRegister(alloc.reg2());
    case RValueAllocation::UNTYPED_STACK_STACK:
      return hasStack(alloc.stackOffset()) && hasStack(alloc.stackOffset2());
#elif defined(JS_PUNBOX64)
    case RValueAllocation::UNTYPED_REG:
      return hasRegister(alloc.reg());
    case RValueAllocation::UNTYPED_STACK:
      return hasStack(alloc.stackOffset());
#endif

    case RValueAllocation::RECOVER_INSTRUCTION:
      return hasInstructionResult(alloc.index());
    case RValueAllocation::RI_WITH_DEFAULT_CST:
      return rm == ReadMethod::AlwaysDefault ||
             hasInstructionResult(alloc.index());

    default:
      return true;
  }
}

Value SnapshotIterator::allocationValue(const RValueAllocation& alloc,
                                        ReadMethod rm) {
  switch (alloc.mode()) {
    case RValueAllocation::CONSTANT:
      return ionScript_->getConstant(alloc.index());

    case RValueAllocation::CST_UNDEFINED:
      return UndefinedValue();

    case RValueAllocation::CST_NULL:
      return NullValue();

    case RValueAllocation::DOUBLE_REG:
      return DoubleValue(fromRegister<double>(alloc.fpuReg()));

    case RValueAllocation::ANY_FLOAT_REG:
      return Float32Value(fromRegister<float>(alloc.fpuReg()));

    case RValueAllocation::ANY_FLOAT_STACK:
      return Float32Value(ReadFrameFloat32Slot(fp_, alloc.stackOffset()));

    case RValueAllocation::TYPED_REG:
      return FromTypedPayload(alloc.knownType(), fromRegister(alloc.reg2()));

    case RValueAllocation::TYPED_STACK: {
      switch (alloc.knownType()) {
        case JSVAL_TYPE_DOUBLE:
          return DoubleValue(ReadFrameDoubleSlot(fp_, alloc.stackOffset2()));
        case JSVAL_TYPE_INT32:
          return Int32Value(ReadFrameInt32Slot(fp_, alloc.stackOffset2()));
        case JSVAL_TYPE_BOOLEAN:
          return BooleanValue(ReadFrameBooleanSlot(fp_, alloc.stackOffset2()));
        case JSVAL_TYPE_STRING:
          return FromStringPayload(fromStack(alloc.stackOffset2()));
        case JSVAL_TYPE_SYMBOL:
          return FromSymbolPayload(fromStack(alloc.stackOffset2()));
        case JSVAL_TYPE_BIGINT:
          return FromBigIntPayload(fromStack(alloc.stackOffset2()));
        case JSVAL_TYPE_OBJECT:
          return FromObjectPayload(fromStack(alloc.stackOffset2()));
        default:
          MOZ_CRASH("Unexpected type");
      }
    }

#if defined(JS_NUNBOX32)
    case RValueAllocation::UNTYPED_REG_REG: {
      return Value::fromTagAndPayload(JSValueTag(fromRegister(alloc.reg())),
                                      fromRegister(alloc.reg2()));
    }

    case RValueAllocation::UNTYPED_REG_STACK: {
      return Value::fromTagAndPayload(JSValueTag(fromRegister(alloc.reg())),
                                      fromStack(alloc.stackOffset2()));
    }

    case RValueAllocation::UNTYPED_STACK_REG: {
      return Value::fromTagAndPayload(
          JSValueTag(fromStack(alloc.stackOffset())),
          fromRegister(alloc.reg2()));
    }

    case RValueAllocation::UNTYPED_STACK_STACK: {
      return Value::fromTagAndPayload(
          JSValueTag(fromStack(alloc.stackOffset())),
          fromStack(alloc.stackOffset2()));
    }
#elif defined(JS_PUNBOX64)
    case RValueAllocation::UNTYPED_REG: {
      return Value::fromRawBits(fromRegister(alloc.reg()));
    }

    case RValueAllocation::UNTYPED_STACK: {
      return Value::fromRawBits(fromStack(alloc.stackOffset()));
    }
#endif

    case RValueAllocation::RECOVER_INSTRUCTION:
      return fromInstructionResult(alloc.index());

    case RValueAllocation::RI_WITH_DEFAULT_CST:
      if (rm == ReadMethod::Normal && hasInstructionResult(alloc.index())) {
        return fromInstructionResult(alloc.index());
      }
      MOZ_ASSERT(rm == ReadMethod::AlwaysDefault);
      return ionScript_->getConstant(alloc.index2());

    default:
      MOZ_CRASH("huh?");
  }
}

Value SnapshotIterator::maybeRead(const RValueAllocation& a,
                                  MaybeReadFallback& fallback) {
  if (allocationReadable(a)) {
    return allocationValue(a);
  }

  if (fallback.canRecoverResults()) {
    // Code paths which are calling maybeRead are not always capable of
    // returning an error code, as these code paths used to be infallible.
    AutoEnterOOMUnsafeRegion oomUnsafe;
    if (!initInstructionResults(fallback)) {
      oomUnsafe.crash("js::jit::SnapshotIterator::maybeRead");
    }

    if (allocationReadable(a)) {
      return allocationValue(a);
    }

    MOZ_ASSERT_UNREACHABLE("All allocations should be readable.");
  }

  return UndefinedValue();
}

bool SnapshotIterator::tryRead(Value* result) {
  RValueAllocation a = readAllocation();
  if (allocationReadable(a)) {
    *result = allocationValue(a);
    return true;
  }
  return false;
}

void SnapshotIterator::writeAllocationValuePayload(
    const RValueAllocation& alloc, const Value& v) {
  MOZ_ASSERT(v.isGCThing());

  switch (alloc.mode()) {
    case RValueAllocation::CONSTANT:
      ionScript_->getConstant(alloc.index()) = v;
      break;

    case RValueAllocation::CST_UNDEFINED:
    case RValueAllocation::CST_NULL:
    case RValueAllocation::DOUBLE_REG:
    case RValueAllocation::ANY_FLOAT_REG:
    case RValueAllocation::ANY_FLOAT_STACK:
      MOZ_CRASH("Not a GC thing: Unexpected write");
      break;

    case RValueAllocation::TYPED_REG:
      machine_->write(alloc.reg2(), uintptr_t(v.toGCThing()));
      break;

    case RValueAllocation::TYPED_STACK:
      switch (alloc.knownType()) {
        default:
          MOZ_CRASH("Not a GC thing: Unexpected write");
          break;
        case JSVAL_TYPE_STRING:
        case JSVAL_TYPE_SYMBOL:
        case JSVAL_TYPE_BIGINT:
        case JSVAL_TYPE_OBJECT:
          WriteFrameSlot(fp_, alloc.stackOffset2(), uintptr_t(v.toGCThing()));
          break;
      }
      break;

#if defined(JS_NUNBOX32)
    case RValueAllocation::UNTYPED_REG_REG:
    case RValueAllocation::UNTYPED_STACK_REG:
      machine_->write(alloc.reg2(), uintptr_t(v.toGCThing()));
      break;

    case RValueAllocation::UNTYPED_REG_STACK:
    case RValueAllocation::UNTYPED_STACK_STACK:
      WriteFrameSlot(fp_, alloc.stackOffset2(), uintptr_t(v.toGCThing()));
      break;
#elif defined(JS_PUNBOX64)
    case RValueAllocation::UNTYPED_REG:
      machine_->write(alloc.reg(), v.asRawBits());
      break;

    case RValueAllocation::UNTYPED_STACK:
      WriteFrameSlot(fp_, alloc.stackOffset(), v.asRawBits());
      break;
#endif

    case RValueAllocation::RECOVER_INSTRUCTION:
      MOZ_CRASH("Recover instructions are handled by the JitActivation.");
      break;

    case RValueAllocation::RI_WITH_DEFAULT_CST:
      // Assume that we are always going to be writing on the default value
      // while tracing.
      ionScript_->getConstant(alloc.index2()) = v;
      break;

    default:
      MOZ_CRASH("huh?");
  }
}

void SnapshotIterator::traceAllocation(JSTracer* trc) {
  RValueAllocation alloc = readAllocation();
  if (!allocationReadable(alloc, ReadMethod::AlwaysDefault)) {
    return;
  }

  Value v = allocationValue(alloc, ReadMethod::AlwaysDefault);
  if (!v.isGCThing()) {
    return;
  }

  Value copy = v;
  TraceRoot(trc, &v, "ion-typed-reg");
  if (v != copy) {
    MOZ_ASSERT(SameType(v, copy));
    writeAllocationValuePayload(alloc, v);
  }
}

const RResumePoint* SnapshotIterator::resumePoint() const {
  return instruction()->toResumePoint();
}

uint32_t SnapshotIterator::numAllocations() const {
  return instruction()->numOperands();
}

uint32_t SnapshotIterator::pcOffset() const {
  return resumePoint()->pcOffset();
}

ResumeMode SnapshotIterator::resumeMode() const {
  return resumePoint()->mode();
}

void SnapshotIterator::skipInstruction() {
  MOZ_ASSERT(snapshot_.numAllocationsRead() == 0);
  size_t numOperands = instruction()->numOperands();
  for (size_t i = 0; i < numOperands; i++) {
    skip();
  }
  nextInstruction();
}

bool SnapshotIterator::initInstructionResults(MaybeReadFallback& fallback) {
  MOZ_ASSERT(fallback.canRecoverResults());
  JSContext* cx = fallback.maybeCx;

  // If there is only one resume point in the list of instructions, then there
  // is no instruction to recover, and thus no need to register any results.
  if (recover_.numInstructions() == 1) {
    return true;
  }

  JitFrameLayout* fp = fallback.frame->jsFrame();
  RInstructionResults* results = fallback.activation->maybeIonFrameRecovery(fp);
  if (!results) {
    AutoRealm ar(cx, fallback.frame->script());

    // We are going to run recover instructions. To avoid problems where recover
    // instructions are not idempotent (for example, if we allocate an object,
    // object identity may be observable), we should not execute code in the
    // Ion stack frame afterwards. To avoid doing so, we invalidate the script.
    // This is not necessary for bailouts or other cases where we are leaving
    // the frame anyway. We only need it for niche cases like debugger
    // introspection or Function.arguments.
    if (fallback.consequence == MaybeReadFallback::Fallback_Invalidate) {
      ionScript_->invalidate(cx, fallback.frame->script(),
                             /* resetUses = */ false,
                             "Observe recovered instruction.");
    }

    // Register the list of result on the activation.  We need to do that
    // before we initialize the list such as if any recover instruction
    // cause a GC, we can ensure that the results are properly traced by the
    // activation.
    RInstructionResults tmp(fallback.frame->jsFrame());
    if (!fallback.activation->registerIonFrameRecovery(std::move(tmp))) {
      return false;
    }

    results = fallback.activation->maybeIonFrameRecovery(fp);

    // Start a new snapshot at the beginning of the JSJitFrameIter.  This
    // SnapshotIterator is used for evaluating the content of all recover
    // instructions.  The result is then saved on the JitActivation.
    MachineState machine = fallback.frame->machineState();
    SnapshotIterator s(*fallback.frame, &machine);
    if (!s.computeInstructionResults(cx, results)) {
      // If the evaluation failed because of OOMs, then we discard the
      // current set of result that we collected so far.
      fallback.activation->removeIonFrameRecovery(fp);
      return false;
    }
  }

  MOZ_ASSERT(results->isInitialized());
  MOZ_RELEASE_ASSERT(results->length() == recover_.numInstructions() - 1);
  instructionResults_ = results;
  return true;
}

bool SnapshotIterator::computeInstructionResults(
    JSContext* cx, RInstructionResults* results) const {
  MOZ_ASSERT(!results->isInitialized());
  MOZ_ASSERT(recover_.numInstructionsRead() == 1);

  // The last instruction will always be a resume point.
  size_t numResults = recover_.numInstructions() - 1;
  if (!results->isInitialized()) {
    if (!results->init(cx, numResults)) {
      return false;
    }

    // No need to iterate over the only resume point.
    if (!numResults) {
      MOZ_ASSERT(results->isInitialized());
      return true;
    }

    // Avoid invoking the object metadata callback, which could try to walk the
    // stack while bailing out.
    gc::AutoSuppressGC suppressGC(cx);
    js::AutoSuppressAllocationMetadataBuilder suppressMetadata(cx);

    // Fill with the results of recover instructions.
    SnapshotIterator s(*this);
    s.instructionResults_ = results;
    while (s.moreInstructions()) {
      // Skip resume point and only interpret recover instructions.
      if (s.instruction()->isResumePoint()) {
        s.skipInstruction();
        continue;
      }

      if (!s.instruction()->recover(cx, s)) {
        return false;
      }
      s.nextInstruction();
    }
  }

  MOZ_ASSERT(results->isInitialized());
  return true;
}

void SnapshotIterator::storeInstructionResult(const Value& v) {
  uint32_t currIns = recover_.numInstructionsRead() - 1;
  MOZ_ASSERT((*instructionResults_)[currIns].isMagic(JS_ION_BAILOUT));
  (*instructionResults_)[currIns] = v;
}

Value SnapshotIterator::fromInstructionResult(uint32_t index) const {
  MOZ_ASSERT(!(*instructionResults_)[index].isMagic(JS_ION_BAILOUT));
  return (*instructionResults_)[index];
}

void SnapshotIterator::settleOnFrame() {
  // Check that the current instruction can still be use.
  MOZ_ASSERT(snapshot_.numAllocationsRead() == 0);
  while (!instruction()->isResumePoint()) {
    skipInstruction();
  }
}

void SnapshotIterator::nextFrame() {
  nextInstruction();
  settleOnFrame();
}

Value SnapshotIterator::maybeReadAllocByIndex(size_t index) {
  while (index--) {
    MOZ_ASSERT(moreAllocations());
    skip();
  }

  Value s;
  {
    // This MaybeReadFallback method cannot GC.
    JS::AutoSuppressGCAnalysis nogc;
    MaybeReadFallback fallback;
    s = maybeRead(fallback);
  }

  while (moreAllocations()) {
    skip();
  }

  return s;
}

InlineFrameIterator::InlineFrameIterator(JSContext* cx,
                                         const JSJitFrameIter* iter)
    : calleeTemplate_(cx), script_(cx), pc_(nullptr), numActualArgs_(0) {
  resetOn(iter);
}

InlineFrameIterator::InlineFrameIterator(JSContext* cx,
                                         const InlineFrameIterator* iter)
    : frame_(iter ? iter->frame_ : nullptr),
      framesRead_(0),
      frameCount_(iter ? iter->frameCount_ : UINT32_MAX),
      calleeTemplate_(cx),
      script_(cx),
      pc_(nullptr),
      numActualArgs_(0) {
  if (frame_) {
    machine_ = iter->machine_;
    start_ = SnapshotIterator(*frame_, &machine_);

    // findNextFrame will iterate to the next frame and init. everything.
    // Therefore to settle on the same frame, we report one frame less readed.
    framesRead_ = iter->framesRead_ - 1;
    findNextFrame();
  }
}

void InlineFrameIterator::resetOn(const JSJitFrameIter* iter) {
  frame_ = iter;
  framesRead_ = 0;
  frameCount_ = UINT32_MAX;

  if (iter) {
    machine_ = iter->machineState();
    start_ = SnapshotIterator(*iter, &machine_);
    findNextFrame();
  }
}

void InlineFrameIterator::findNextFrame() {
  MOZ_ASSERT(more());

  si_ = start_;

  // Read the initial frame out of the C stack.
  calleeTemplate_ = frame_->maybeCallee();
  calleeRVA_ = RValueAllocation();
  script_ = frame_->script();
  MOZ_ASSERT(script_->hasBaselineScript());

  // Settle on the outermost frame without evaluating any instructions before
  // looking for a pc.
  si_.settleOnFrame();

  pc_ = script_->offsetToPC(si_.pcOffset());
  numActualArgs_ = 0xbadbad;

  // This unfortunately is O(n*m), because we must skip over outer frames
  // before reading inner ones.

  // The first time (frameCount_ == UINT32_MAX) we do not know the number of
  // frames that we are going to inspect.  So we are iterating until there is
  // no more frames, to settle on the inner most frame and to count the number
  // of frames.
  size_t remaining = (frameCount_ != UINT32_MAX) ? frameNo() - 1 : SIZE_MAX;

  size_t i = 1;
  for (; i <= remaining && si_.moreFrames(); i++) {
    ResumeMode mode = si_.resumeMode();
    MOZ_ASSERT(IsIonInlinableOp(JSOp(*pc_)));

    // Recover the number of actual arguments from the script.
    if (IsInvokeOp(JSOp(*pc_))) {
      MOZ_ASSERT(mode == ResumeMode::InlinedStandardCall ||
                 mode == ResumeMode::InlinedFunCall);
      numActualArgs_ = GET_ARGC(pc_);
      if (mode == ResumeMode::InlinedFunCall && numActualArgs_ > 0) {
        numActualArgs_--;
      }
    } else if (IsGetPropPC(pc_) || IsGetElemPC(pc_)) {
      MOZ_ASSERT(mode == ResumeMode::InlinedAccessor);
      numActualArgs_ = 0;
    } else {
      MOZ_RELEASE_ASSERT(IsSetPropPC(pc_));
      MOZ_ASSERT(mode == ResumeMode::InlinedAccessor);
      numActualArgs_ = 1;
    }

    // Skip over non-argument slots, as well as |this|.
    bool skipNewTarget = IsConstructPC(pc_);
    unsigned skipCount =
        (si_.numAllocations() - 1) - numActualArgs_ - 1 - skipNewTarget;
    for (unsigned j = 0; j < skipCount; j++) {
      si_.skip();
    }

    // This value should correspond to the function which is being inlined.
    // The value must be readable to iterate over the inline frame. Most of
    // the time, these functions are stored as JSFunction constants,
    // register which are holding the JSFunction pointer, or recover
    // instruction with Default value.
    Value funval = si_.readWithDefault(&calleeRVA_);

    // Skip extra value allocations.
    while (si_.moreAllocations()) {
      si_.skip();
    }

    si_.nextFrame();

    calleeTemplate_ = &funval.toObject().as<JSFunction>();
    script_ = calleeTemplate_->nonLazyScript();
    MOZ_ASSERT(script_->hasBaselineScript());

    pc_ = script_->offsetToPC(si_.pcOffset());
  }

  // The first time we do not know the number of frames, we only settle on the
  // last frame, and update the number of frames based on the number of
  // iteration that we have done.
  if (frameCount_ == UINT32_MAX) {
    MOZ_ASSERT(!si_.moreFrames());
    frameCount_ = i;
  }

  framesRead_++;
}

JSFunction* InlineFrameIterator::callee(MaybeReadFallback& fallback) const {
  MOZ_ASSERT(isFunctionFrame());
  if (calleeRVA_.mode() == RValueAllocation::INVALID ||
      !fallback.canRecoverResults()) {
    return calleeTemplate_;
  }

  SnapshotIterator s(si_);
  // :TODO: Handle allocation failures from recover instruction.
  Value funval = s.maybeRead(calleeRVA_, fallback);
  return &funval.toObject().as<JSFunction>();
}

JSObject* InlineFrameIterator::computeEnvironmentChain(
    const Value& envChainValue, MaybeReadFallback& fallback,
    bool* hasInitialEnv) const {
  if (envChainValue.isObject()) {
    if (hasInitialEnv) {
      if (fallback.canRecoverResults()) {
        RootedObject obj(fallback.maybeCx, &envChainValue.toObject());
        *hasInitialEnv = isFunctionFrame() &&
                         callee(fallback)->needsFunctionEnvironmentObjects();
        return obj;
      }
      JS::AutoSuppressGCAnalysis
          nogc;  // If we cannot recover then we cannot GC.
      *hasInitialEnv = isFunctionFrame() &&
                       callee(fallback)->needsFunctionEnvironmentObjects();
    }

    return &envChainValue.toObject();
  }

  // Note we can hit this case even for functions with a CallObject, in case
  // we are walking the frame during the function prologue, before the env
  // chain has been initialized.
  if (isFunctionFrame()) {
    return callee(fallback)->environment();
  }

  if (isModuleFrame()) {
    return script()->module()->environment();
  }

  // Ion does not handle non-function scripts that have anything other than
  // the global on their env chain.
  MOZ_ASSERT(!script()->isForEval());
  MOZ_ASSERT(!script()->hasNonSyntacticScope());
  return &script()->global().lexicalEnvironment();
}

bool InlineFrameIterator::isFunctionFrame() const { return !!calleeTemplate_; }

bool InlineFrameIterator::isModuleFrame() const { return script()->isModule(); }

uintptr_t* MachineState::SafepointState::addressOfRegister(Register reg) const {
  size_t offset = regs.offsetOfPushedRegister(reg);

  MOZ_ASSERT((offset % sizeof(uintptr_t)) == 0);
  uint32_t index = offset / sizeof(uintptr_t);

#ifdef DEBUG
  // Assert correctness with a slower algorithm in debug builds.
  uint32_t expectedIndex = 0;
  bool found = false;
  for (GeneralRegisterBackwardIterator iter(regs); iter.more(); ++iter) {
    expectedIndex++;
    if (*iter == reg) {
      found = true;
      break;
    }
  }
  MOZ_ASSERT(found);
  MOZ_ASSERT(expectedIndex == index);
#endif

  return spillBase - index;
}

char* MachineState::SafepointState::addressOfRegister(FloatRegister reg) const {
  // Note: this could be optimized similar to the GPR case above by implementing
  // offsetOfPushedRegister for FloatRegisterSet. Float register sets are
  // complicated though and this case is very uncommon: it's only reachable for
  // exception bailouts with live float registers.
  MOZ_ASSERT(!reg.isSimd128());
  char* ptr = floatSpillBase;
  for (FloatRegisterBackwardIterator iter(floatRegs); iter.more(); ++iter) {
    ptr -= (*iter).size();
    for (uint32_t a = 0; a < (*iter).numAlignedAliased(); a++) {
      // Only say that registers that actually start here start here.
      // e.g. d0 should not start at s1, only at s0.
      FloatRegister ftmp = (*iter).alignedAliased(a);
      if (ftmp == reg) {
        return ptr;
      }
    }
  }
  MOZ_CRASH("Invalid register");
}

uintptr_t MachineState::read(Register reg) const {
  if (state_.is<BailoutState>()) {
    return state_.as<BailoutState>().regs[reg.code()].r;
  }
  if (state_.is<SafepointState>()) {
    uintptr_t* addr = state_.as<SafepointState>().addressOfRegister(reg);
    return *addr;
  }
  MOZ_CRASH("Invalid state");
}

template <typename T>
T MachineState::read(FloatRegister reg) const {
#if !defined(JS_CODEGEN_RISCV64)
  MOZ_ASSERT(reg.size() == sizeof(T));
#else
  // RISCV64 always store FloatRegister as 64bit.
  MOZ_ASSERT(reg.size() == sizeof(double));
#endif

#if !defined(JS_CODEGEN_NONE) && !defined(JS_CODEGEN_WASM32)
  if (state_.is<BailoutState>()) {
    uint32_t offset = reg.getRegisterDumpOffsetInBytes();
    MOZ_ASSERT((offset % sizeof(T)) == 0);
    MOZ_ASSERT((offset + sizeof(T)) <= sizeof(RegisterDump::FPUArray));

    const BailoutState& state = state_.as<BailoutState>();
    char* addr = reinterpret_cast<char*>(state.floatRegs.begin()) + offset;
    return *reinterpret_cast<T*>(addr);
  }
  if (state_.is<SafepointState>()) {
    char* addr = state_.as<SafepointState>().addressOfRegister(reg);
    return *reinterpret_cast<T*>(addr);
  }
#endif
  MOZ_CRASH("Invalid state");
}

void MachineState::write(Register reg, uintptr_t value) const {
  if (state_.is<SafepointState>()) {
    uintptr_t* addr = state_.as<SafepointState>().addressOfRegister(reg);
    *addr = value;
    return;
  }
  MOZ_CRASH("Invalid state");
}

bool InlineFrameIterator::isConstructing() const {
  // Skip the current frame and look at the caller's.
  if (more()) {
    InlineFrameIterator parent(TlsContext.get(), this);
    ++parent;

    // In the case of a JS frame, look up the pc from the snapshot.
    JSOp parentOp = JSOp(*parent.pc());

    // Inlined Getters and Setters are never constructing.
    if (IsIonInlinableGetterOrSetterOp(parentOp)) {
      return false;
    }

    MOZ_ASSERT(IsInvokeOp(parentOp) && !IsSpreadOp(parentOp));

    return IsConstructOp(parentOp);
  }

  return frame_->isConstructing();
}

void SnapshotIterator::warnUnreadableAllocation() {
  fprintf(stderr,
          "Warning! Tried to access unreadable value allocation (possible "
          "f.arguments).\n");
}

struct DumpOverflownOp {
  const unsigned numFormals_;
  unsigned i_ = 0;

  explicit DumpOverflownOp(unsigned numFormals) : numFormals_(numFormals) {}

  void operator()(const Value& v) {
    if (i_ >= numFormals_) {
      fprintf(stderr, "  actual (arg %u): ", i_);
#if defined(DEBUG) || defined(JS_JITSPEW)
      DumpValue(v);
#else
      fprintf(stderr, "?\n");
#endif
    }
    i_++;
  }
};

void InlineFrameIterator::dump() const {
  MaybeReadFallback fallback;

  if (more()) {
    fprintf(stderr, " JS frame (inlined)\n");
  } else {
    fprintf(stderr, " JS frame\n");
  }

  bool isFunction = false;
  if (isFunctionFrame()) {
    isFunction = true;
    fprintf(stderr, "  callee fun: ");
#if defined(DEBUG) || defined(JS_JITSPEW)
    DumpObject(callee(fallback));
#else
    fprintf(stderr, "?\n");
#endif
  } else {
    fprintf(stderr, "  global frame, no callee\n");
  }

  fprintf(stderr, "  file %s line %u\n", script()->filename(),
          script()->lineno());

  fprintf(stderr, "  script = %p, pc = %p\n", (void*)script(), pc());
  fprintf(stderr, "  current op: %s\n", CodeName(JSOp(*pc())));

  if (!more()) {
    numActualArgs();
  }

  SnapshotIterator si = snapshotIterator();
  fprintf(stderr, "  slots: %u\n", si.numAllocations() - 1);
  for (unsigned i = 0; i < si.numAllocations() - 1; i++) {
    if (isFunction) {
      if (i == 0) {
        fprintf(stderr, "  env chain: ");
      } else if (i == 1) {
        fprintf(stderr, "  this: ");
      } else if (i - 2 < calleeTemplate()->nargs()) {
        fprintf(stderr, "  formal (arg %u): ", i - 2);
      } else {
        if (i - 2 == calleeTemplate()->nargs() &&
            numActualArgs() > calleeTemplate()->nargs()) {
          DumpOverflownOp d(calleeTemplate()->nargs());
          unaliasedForEachActual(TlsContext.get(), d, fallback);
        }

        fprintf(stderr, "  slot %d: ", int(i - 2 - calleeTemplate()->nargs()));
      }
    } else
      fprintf(stderr, "  slot %u: ", i);
#if defined(DEBUG) || defined(JS_JITSPEW)
    DumpValue(si.maybeRead(fallback));
#else
    fprintf(stderr, "?\n");
#endif
  }

  fputc('\n', stderr);
}

JitFrameLayout* InvalidationBailoutStack::fp() const {
  return (JitFrameLayout*)(sp() + ionScript_->frameSize());
}

void InvalidationBailoutStack::checkInvariants() const {
#ifdef DEBUG
  JitFrameLayout* frame = fp();
  CalleeToken token = frame->calleeToken();
  MOZ_ASSERT(token);

  uint8_t* rawBase = ionScript()->method()->raw();
  uint8_t* rawLimit = rawBase + ionScript()->method()->instructionsSize();
  uint8_t* osiPoint = osiPointReturnAddress();
  MOZ_ASSERT(rawBase <= osiPoint && osiPoint <= rawLimit);
#endif
}

void AssertJitStackInvariants(JSContext* cx) {
  for (JitActivationIterator activations(cx); !activations.done();
       ++activations) {
    JitFrameIter iter(activations->asJit());
    if (iter.isJSJit()) {
      JSJitFrameIter& frames = iter.asJSJit();
      size_t prevFrameSize = 0;
      size_t frameSize = 0;
      bool isScriptedCallee = false;
      for (; !frames.done(); ++frames) {
        size_t calleeFp = reinterpret_cast<size_t>(frames.fp());
        size_t callerFp = reinterpret_cast<size_t>(frames.prevFp());
        MOZ_ASSERT(callerFp >= calleeFp);
        prevFrameSize = frameSize;
        frameSize = callerFp - calleeFp;

        if (frames.isScripted() &&
            (frames.prevType() == FrameType::Rectifier ||
             frames.prevType() == FrameType::BaselineInterpreterEntry)) {
          MOZ_RELEASE_ASSERT(
              frameSize % JitStackAlignment == 0,
              "The rectifier and bli entry frame should keep the alignment");

          size_t expectedFrameSize =
              sizeof(Value) *
                  (frames.callee()->nargs() + 1 /* |this| argument */ +
                   frames.isConstructing() /* new.target */) +
              sizeof(JitFrameLayout);
          MOZ_RELEASE_ASSERT(frameSize >= expectedFrameSize,
                             "The frame is large enough to hold all arguments");
          MOZ_RELEASE_ASSERT(expectedFrameSize + JitStackAlignment > frameSize,
                             "The frame size is optimal");
        }

        if (frames.isExitFrame()) {
          // For the moment, we do not keep the JitStackAlignment
          // alignment for exit frames.
          frameSize -= ExitFrameLayout::Size();
        }

        if (frames.isIonJS()) {
          // Ideally, we should not have such requirement, but keep the
          // alignment-delta as part of the Safepoint such that we can pad
          // accordingly when making out-of-line calls.  In the mean time,
          // let us have check-points where we can garantee that
          // everything can properly be aligned before adding complexity.
          MOZ_RELEASE_ASSERT(
              frames.ionScript()->frameSize() % JitStackAlignment == 0,
              "Ensure that if the Ion frame is aligned, then the spill base is "
              "also aligned");

          if (isScriptedCallee) {
            MOZ_RELEASE_ASSERT(prevFrameSize % JitStackAlignment == 0,
                               "The ion frame should keep the alignment");
          }
        }

        // The stack is dynamically aligned by baseline stubs before calling
        // any jitted code.
        if (frames.prevType() == FrameType::BaselineStub && isScriptedCallee) {
          MOZ_RELEASE_ASSERT(calleeFp % JitStackAlignment == 0,
                             "The baseline stub restores the stack alignment");
        }

        isScriptedCallee =
            frames.isScripted() || frames.type() == FrameType::Rectifier;
      }

      MOZ_RELEASE_ASSERT(
          JSJitFrameIter::isEntry(frames.type()),
          "The first frame of a Jit activation should be an entry frame");
      MOZ_RELEASE_ASSERT(
          reinterpret_cast<size_t>(frames.fp()) % JitStackAlignment == 0,
          "The entry frame should be properly aligned");
    } else {
      MOZ_ASSERT(iter.isWasm());
      wasm::WasmFrameIter& frames = iter.asWasm();
      while (!frames.done()) {
        ++frames;
      }
    }
  }
}

}  // namespace jit
}  // namespace js