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
|
// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package ssa
// This file implements the BUILD phase of SSA construction.
//
// SSA construction has two phases, CREATE and BUILD. In the CREATE phase
// (create.go), all packages are constructed and type-checked and
// definitions of all package members are created, method-sets are
// computed, and wrapper methods are synthesized.
// ssa.Packages are created in arbitrary order.
//
// In the BUILD phase (builder.go), the builder traverses the AST of
// each Go source function and generates SSA instructions for the
// function body. Initializer expressions for package-level variables
// are emitted to the package's init() function in the order specified
// by go/types.Info.InitOrder, then code for each function in the
// package is generated in lexical order.
// The BUILD phases for distinct packages are independent and are
// executed in parallel.
//
// TODO(adonovan): indeed, building functions is now embarrassingly parallel.
// Audit for concurrency then benchmark using more goroutines.
//
// The builder's and Program's indices (maps) are populated and
// mutated during the CREATE phase, but during the BUILD phase they
// remain constant. The sole exception is Prog.methodSets and its
// related maps, which are protected by a dedicated mutex.
import (
"fmt"
"go/ast"
exact "go/constant"
"go/token"
"go/types"
"os"
"sync"
)
type opaqueType struct {
types.Type
name string
}
func (t *opaqueType) String() string { return t.name }
var (
varOk = newVar("ok", tBool)
varIndex = newVar("index", tInt)
// Type constants.
tBool = types.Typ[types.Bool]
tByte = types.Typ[types.Byte]
tInt = types.Typ[types.Int]
tInvalid = types.Typ[types.Invalid]
tString = types.Typ[types.String]
tUntypedNil = types.Typ[types.UntypedNil]
tRangeIter = &opaqueType{nil, "iter"} // the type of all "range" iterators
tEface = types.NewInterface(nil, nil).Complete()
// SSA Value constants.
vZero = intConst(0)
vOne = intConst(1)
vTrue = NewConst(exact.MakeBool(true), tBool)
)
// builder holds state associated with the package currently being built.
// Its methods contain all the logic for AST-to-SSA conversion.
type builder struct{}
// cond emits to fn code to evaluate boolean condition e and jump
// to t or f depending on its value, performing various simplifications.
//
// Postcondition: fn.currentBlock is nil.
//
func (b *builder) cond(fn *Function, e ast.Expr, t, f *BasicBlock) {
switch e := e.(type) {
case *ast.ParenExpr:
b.cond(fn, e.X, t, f)
return
case *ast.BinaryExpr:
switch e.Op {
case token.LAND:
ltrue := fn.newBasicBlock("cond.true")
b.cond(fn, e.X, ltrue, f)
fn.currentBlock = ltrue
b.cond(fn, e.Y, t, f)
return
case token.LOR:
lfalse := fn.newBasicBlock("cond.false")
b.cond(fn, e.X, t, lfalse)
fn.currentBlock = lfalse
b.cond(fn, e.Y, t, f)
return
}
case *ast.UnaryExpr:
if e.Op == token.NOT {
b.cond(fn, e.X, f, t)
return
}
}
// A traditional compiler would simplify "if false" (etc) here
// but we do not, for better fidelity to the source code.
//
// The value of a constant condition may be platform-specific,
// and may cause blocks that are reachable in some configuration
// to be hidden from subsequent analyses such as bug-finding tools.
emitIf(fn, b.expr(fn, e), t, f)
}
// logicalBinop emits code to fn to evaluate e, a &&- or
// ||-expression whose reified boolean value is wanted.
// The value is returned.
//
func (b *builder) logicalBinop(fn *Function, e *ast.BinaryExpr) Value {
rhs := fn.newBasicBlock("binop.rhs")
done := fn.newBasicBlock("binop.done")
// T(e) = T(e.X) = T(e.Y) after untyped constants have been
// eliminated.
// TODO(adonovan): not true; MyBool==MyBool yields UntypedBool.
t := fn.Pkg.typeOf(e)
var short Value // value of the short-circuit path
switch e.Op {
case token.LAND:
b.cond(fn, e.X, rhs, done)
short = NewConst(exact.MakeBool(false), t)
case token.LOR:
b.cond(fn, e.X, done, rhs)
short = NewConst(exact.MakeBool(true), t)
}
// Is rhs unreachable?
if rhs.Preds == nil {
// Simplify false&&y to false, true||y to true.
fn.currentBlock = done
return short
}
// Is done unreachable?
if done.Preds == nil {
// Simplify true&&y (or false||y) to y.
fn.currentBlock = rhs
return b.expr(fn, e.Y)
}
// All edges from e.X to done carry the short-circuit value.
var edges []Value
for range done.Preds {
edges = append(edges, short)
}
// The edge from e.Y to done carries the value of e.Y.
fn.currentBlock = rhs
edges = append(edges, b.expr(fn, e.Y))
emitJump(fn, done)
fn.currentBlock = done
phi := &Phi{Edges: edges, Comment: e.Op.String()}
phi.pos = e.OpPos
phi.typ = t
return done.emit(phi)
}
// exprN lowers a multi-result expression e to SSA form, emitting code
// to fn and returning a single Value whose type is a *types.Tuple.
// The caller must access the components via Extract.
//
// Multi-result expressions include CallExprs in a multi-value
// assignment or return statement, and "value,ok" uses of
// TypeAssertExpr, IndexExpr (when X is a map), and UnaryExpr (when Op
// is token.ARROW).
//
func (b *builder) exprN(fn *Function, e ast.Expr) Value {
typ := fn.Pkg.typeOf(e).(*types.Tuple)
switch e := e.(type) {
case *ast.ParenExpr:
return b.exprN(fn, e.X)
case *ast.CallExpr:
// Currently, no built-in function nor type conversion
// has multiple results, so we can avoid some of the
// cases for single-valued CallExpr.
var c Call
b.setCall(fn, e, &c.Call)
c.typ = typ
return fn.emit(&c)
case *ast.IndexExpr:
mapt := fn.Pkg.typeOf(e.X).Underlying().(*types.Map)
lookup := &Lookup{
X: b.expr(fn, e.X),
Index: emitConv(fn, b.expr(fn, e.Index), mapt.Key()),
CommaOk: true,
}
lookup.setType(typ)
lookup.setPos(e.Lbrack)
return fn.emit(lookup)
case *ast.TypeAssertExpr:
return emitTypeTest(fn, b.expr(fn, e.X), typ.At(0).Type(), e.Lparen)
case *ast.UnaryExpr: // must be receive <-
unop := &UnOp{
Op: token.ARROW,
X: b.expr(fn, e.X),
CommaOk: true,
}
unop.setType(typ)
unop.setPos(e.OpPos)
return fn.emit(unop)
}
panic(fmt.Sprintf("exprN(%T) in %s", e, fn))
}
// builtin emits to fn SSA instructions to implement a call to the
// built-in function obj with the specified arguments
// and return type. It returns the value defined by the result.
//
// The result is nil if no special handling was required; in this case
// the caller should treat this like an ordinary library function
// call.
//
func (b *builder) builtin(fn *Function, obj *types.Builtin, args []ast.Expr, typ types.Type, pos token.Pos) Value {
switch obj.Name() {
case "make":
switch typ.Underlying().(type) {
case *types.Slice:
n := b.expr(fn, args[1])
m := n
if len(args) == 3 {
m = b.expr(fn, args[2])
}
if m, ok := m.(*Const); ok {
// treat make([]T, n, m) as new([m]T)[:n]
cap := m.Int64()
at := types.NewArray(typ.Underlying().(*types.Slice).Elem(), cap)
alloc := emitNew(fn, at, pos)
alloc.Comment = "makeslice"
v := &Slice{
X: alloc,
High: n,
}
v.setPos(pos)
v.setType(typ)
return fn.emit(v)
}
v := &MakeSlice{
Len: n,
Cap: m,
}
v.setPos(pos)
v.setType(typ)
return fn.emit(v)
case *types.Map:
var res Value
if len(args) == 2 {
res = b.expr(fn, args[1])
}
v := &MakeMap{Reserve: res}
v.setPos(pos)
v.setType(typ)
return fn.emit(v)
case *types.Chan:
var sz Value = vZero
if len(args) == 2 {
sz = b.expr(fn, args[1])
}
v := &MakeChan{Size: sz}
v.setPos(pos)
v.setType(typ)
return fn.emit(v)
}
case "new":
alloc := emitNew(fn, deref(typ), pos)
alloc.Comment = "new"
return alloc
case "len", "cap":
// Special case: len or cap of an array or *array is
// based on the type, not the value which may be nil.
// We must still evaluate the value, though. (If it
// was side-effect free, the whole call would have
// been constant-folded.)
t := deref(fn.Pkg.typeOf(args[0])).Underlying()
if at, ok := t.(*types.Array); ok {
b.expr(fn, args[0]) // for effects only
return intConst(at.Len())
}
// Otherwise treat as normal.
case "panic":
fn.emit(&Panic{
X: emitConv(fn, b.expr(fn, args[0]), tEface),
pos: pos,
})
fn.currentBlock = fn.newBasicBlock("unreachable")
return vTrue // any non-nil Value will do
}
return nil // treat all others as a regular function call
}
// addr lowers a single-result addressable expression e to SSA form,
// emitting code to fn and returning the location (an lvalue) defined
// by the expression.
//
// If escaping is true, addr marks the base variable of the
// addressable expression e as being a potentially escaping pointer
// value. For example, in this code:
//
// a := A{
// b: [1]B{B{c: 1}}
// }
// return &a.b[0].c
//
// the application of & causes a.b[0].c to have its address taken,
// which means that ultimately the local variable a must be
// heap-allocated. This is a simple but very conservative escape
// analysis.
//
// Operations forming potentially escaping pointers include:
// - &x, including when implicit in method call or composite literals.
// - a[:] iff a is an array (not *array)
// - references to variables in lexically enclosing functions.
//
func (b *builder) addr(fn *Function, e ast.Expr, escaping bool) lvalue {
switch e := e.(type) {
case *ast.Ident:
if isBlankIdent(e) {
return blank{}
}
obj := fn.Pkg.objectOf(e)
v := fn.Prog.packageLevelValue(obj) // var (address)
if v == nil {
v = fn.lookup(obj, escaping)
}
return &address{addr: v, pos: e.Pos(), expr: e}
case *ast.CompositeLit:
t := deref(fn.Pkg.typeOf(e))
var v *Alloc
if escaping {
v = emitNew(fn, t, e.Lbrace)
} else {
v = fn.addLocal(t, e.Lbrace)
}
v.Comment = "complit"
var sb storebuf
b.compLit(fn, v, e, true, &sb)
sb.emit(fn)
return &address{addr: v, pos: e.Lbrace, expr: e}
case *ast.ParenExpr:
return b.addr(fn, e.X, escaping)
case *ast.SelectorExpr:
sel, ok := fn.Pkg.info.Selections[e]
if !ok {
// qualified identifier
return b.addr(fn, e.Sel, escaping)
}
if sel.Kind() != types.FieldVal {
panic(sel)
}
wantAddr := true
v := b.receiver(fn, e.X, wantAddr, escaping, sel)
last := len(sel.Index()) - 1
return &address{
addr: emitFieldSelection(fn, v, sel.Index()[last], true, e.Sel),
pos: e.Sel.Pos(),
expr: e.Sel,
}
case *ast.IndexExpr:
var x Value
var et types.Type
switch t := fn.Pkg.typeOf(e.X).Underlying().(type) {
case *types.Array:
x = b.addr(fn, e.X, escaping).address(fn)
et = types.NewPointer(t.Elem())
case *types.Pointer: // *array
x = b.expr(fn, e.X)
et = types.NewPointer(t.Elem().Underlying().(*types.Array).Elem())
case *types.Slice:
x = b.expr(fn, e.X)
et = types.NewPointer(t.Elem())
case *types.Map:
return &element{
m: b.expr(fn, e.X),
k: emitConv(fn, b.expr(fn, e.Index), t.Key()),
t: t.Elem(),
pos: e.Lbrack,
}
default:
panic("unexpected container type in IndexExpr: " + t.String())
}
v := &IndexAddr{
X: x,
Index: emitConv(fn, b.expr(fn, e.Index), tInt),
}
v.setPos(e.Lbrack)
v.setType(et)
return &address{addr: fn.emit(v), pos: e.Lbrack, expr: e}
case *ast.StarExpr:
return &address{addr: b.expr(fn, e.X), pos: e.Star, expr: e}
}
panic(fmt.Sprintf("unexpected address expression: %T", e))
}
type store struct {
lhs lvalue
rhs Value
}
type storebuf struct{ stores []store }
func (sb *storebuf) store(lhs lvalue, rhs Value) {
sb.stores = append(sb.stores, store{lhs, rhs})
}
func (sb *storebuf) emit(fn *Function) {
for _, s := range sb.stores {
s.lhs.store(fn, s.rhs)
}
}
// assign emits to fn code to initialize the lvalue loc with the value
// of expression e. If isZero is true, assign assumes that loc holds
// the zero value for its type.
//
// This is equivalent to loc.store(fn, b.expr(fn, e)), but may generate
// better code in some cases, e.g., for composite literals in an
// addressable location.
//
// If sb is not nil, assign generates code to evaluate expression e, but
// not to update loc. Instead, the necessary stores are appended to the
// storebuf sb so that they can be executed later. This allows correct
// in-place update of existing variables when the RHS is a composite
// literal that may reference parts of the LHS.
//
func (b *builder) assign(fn *Function, loc lvalue, e ast.Expr, isZero bool, sb *storebuf) {
// Can we initialize it in place?
if e, ok := unparen(e).(*ast.CompositeLit); ok {
// A CompositeLit never evaluates to a pointer,
// so if the type of the location is a pointer,
// an &-operation is implied.
if _, ok := loc.(blank); !ok { // avoid calling blank.typ()
if isPointer(loc.typ()) {
ptr := b.addr(fn, e, true).address(fn)
// copy address
if sb != nil {
sb.store(loc, ptr)
} else {
loc.store(fn, ptr)
}
return
}
}
if _, ok := loc.(*address); ok {
if isInterface(loc.typ()) {
// e.g. var x interface{} = T{...}
// Can't in-place initialize an interface value.
// Fall back to copying.
} else {
// x = T{...} or x := T{...}
addr := loc.address(fn)
if sb != nil {
b.compLit(fn, addr, e, isZero, sb)
} else {
var sb storebuf
b.compLit(fn, addr, e, isZero, &sb)
sb.emit(fn)
}
// Subtle: emit debug ref for aggregate types only;
// slice and map are handled by store ops in compLit.
switch loc.typ().Underlying().(type) {
case *types.Struct, *types.Array:
emitDebugRef(fn, e, addr, true)
}
return
}
}
}
// simple case: just copy
rhs := b.expr(fn, e)
if sb != nil {
sb.store(loc, rhs)
} else {
loc.store(fn, rhs)
}
}
// expr lowers a single-result expression e to SSA form, emitting code
// to fn and returning the Value defined by the expression.
//
func (b *builder) expr(fn *Function, e ast.Expr) Value {
e = unparen(e)
tv := fn.Pkg.info.Types[e]
// Is expression a constant?
if tv.Value != nil {
return NewConst(tv.Value, tv.Type)
}
var v Value
if tv.Addressable() {
// Prefer pointer arithmetic ({Index,Field}Addr) followed
// by Load over subelement extraction (e.g. Index, Field),
// to avoid large copies.
v = b.addr(fn, e, false).load(fn)
} else {
v = b.expr0(fn, e, tv)
}
if fn.debugInfo() {
emitDebugRef(fn, e, v, false)
}
return v
}
func (b *builder) expr0(fn *Function, e ast.Expr, tv types.TypeAndValue) Value {
switch e := e.(type) {
case *ast.BasicLit:
panic("non-constant BasicLit") // unreachable
case *ast.FuncLit:
fn2 := &Function{
name: fmt.Sprintf("%s$%d", fn.Name(), 1+len(fn.AnonFuncs)),
Signature: fn.Pkg.typeOf(e.Type).Underlying().(*types.Signature),
pos: e.Type.Func,
parent: fn,
Pkg: fn.Pkg,
Prog: fn.Prog,
syntax: e,
}
fn.AnonFuncs = append(fn.AnonFuncs, fn2)
b.buildFunction(fn2)
if fn2.FreeVars == nil {
return fn2
}
v := &MakeClosure{Fn: fn2}
v.setType(tv.Type)
for _, fv := range fn2.FreeVars {
v.Bindings = append(v.Bindings, fv.outer)
fv.outer = nil
}
return fn.emit(v)
case *ast.TypeAssertExpr: // single-result form only
return emitTypeAssert(fn, b.expr(fn, e.X), tv.Type, e.Lparen)
case *ast.CallExpr:
if fn.Pkg.info.Types[e.Fun].IsType() {
// Explicit type conversion, e.g. string(x) or big.Int(x)
x := b.expr(fn, e.Args[0])
y := emitConv(fn, x, tv.Type)
if y != x {
switch y := y.(type) {
case *Convert:
y.pos = e.Lparen
case *ChangeType:
y.pos = e.Lparen
case *MakeInterface:
y.pos = e.Lparen
}
}
return y
}
// Call to "intrinsic" built-ins, e.g. new, make, panic.
if id, ok := unparen(e.Fun).(*ast.Ident); ok {
if obj, ok := fn.Pkg.info.Uses[id].(*types.Builtin); ok {
if v := b.builtin(fn, obj, e.Args, tv.Type, e.Lparen); v != nil {
return v
}
}
}
// Regular function call.
var v Call
b.setCall(fn, e, &v.Call)
v.setType(tv.Type)
return fn.emit(&v)
case *ast.UnaryExpr:
switch e.Op {
case token.AND: // &X --- potentially escaping.
addr := b.addr(fn, e.X, true)
if _, ok := unparen(e.X).(*ast.StarExpr); ok {
// &*p must panic if p is nil (http://golang.org/s/go12nil).
// For simplicity, we'll just (suboptimally) rely
// on the side effects of a load.
// TODO(adonovan): emit dedicated nilcheck.
addr.load(fn)
}
return addr.address(fn)
case token.ADD:
return b.expr(fn, e.X)
case token.NOT, token.ARROW, token.SUB, token.XOR: // ! <- - ^
v := &UnOp{
Op: e.Op,
X: b.expr(fn, e.X),
}
v.setPos(e.OpPos)
v.setType(tv.Type)
return fn.emit(v)
default:
panic(e.Op)
}
case *ast.BinaryExpr:
switch e.Op {
case token.LAND, token.LOR:
return b.logicalBinop(fn, e)
case token.SHL, token.SHR:
fallthrough
case token.ADD, token.SUB, token.MUL, token.QUO, token.REM, token.AND, token.OR, token.XOR, token.AND_NOT:
return emitArith(fn, e.Op, b.expr(fn, e.X), b.expr(fn, e.Y), tv.Type, e.OpPos)
case token.EQL, token.NEQ, token.GTR, token.LSS, token.LEQ, token.GEQ:
cmp := emitCompare(fn, e.Op, b.expr(fn, e.X), b.expr(fn, e.Y), e.OpPos)
// The type of x==y may be UntypedBool.
return emitConv(fn, cmp, DefaultType(tv.Type))
default:
panic("illegal op in BinaryExpr: " + e.Op.String())
}
case *ast.SliceExpr:
var low, high, max Value
var x Value
switch fn.Pkg.typeOf(e.X).Underlying().(type) {
case *types.Array:
// Potentially escaping.
x = b.addr(fn, e.X, true).address(fn)
case *types.Basic, *types.Slice, *types.Pointer: // *array
x = b.expr(fn, e.X)
default:
panic("unreachable")
}
if e.High != nil {
high = b.expr(fn, e.High)
}
if e.Low != nil {
low = b.expr(fn, e.Low)
}
if e.Slice3 {
max = b.expr(fn, e.Max)
}
v := &Slice{
X: x,
Low: low,
High: high,
Max: max,
}
v.setPos(e.Lbrack)
v.setType(tv.Type)
return fn.emit(v)
case *ast.Ident:
obj := fn.Pkg.info.Uses[e]
// Universal built-in or nil?
switch obj := obj.(type) {
case *types.Builtin:
return &Builtin{name: obj.Name(), sig: tv.Type.(*types.Signature)}
case *types.Nil:
return nilConst(tv.Type)
}
// Package-level func or var?
if v := fn.Prog.packageLevelValue(obj); v != nil {
if _, ok := obj.(*types.Var); ok {
return emitLoad(fn, v) // var (address)
}
return v // (func)
}
// Local var.
return emitLoad(fn, fn.lookup(obj, false)) // var (address)
case *ast.SelectorExpr:
sel, ok := fn.Pkg.info.Selections[e]
if !ok {
// qualified identifier
return b.expr(fn, e.Sel)
}
switch sel.Kind() {
case types.MethodExpr:
// (*T).f or T.f, the method f from the method-set of type T.
// The result is a "thunk".
return emitConv(fn, makeThunk(fn.Prog, sel), tv.Type)
case types.MethodVal:
// e.f where e is an expression and f is a method.
// The result is a "bound".
obj := sel.Obj().(*types.Func)
rt := recvType(obj)
wantAddr := isPointer(rt)
escaping := true
v := b.receiver(fn, e.X, wantAddr, escaping, sel)
if isInterface(rt) {
// If v has interface type I,
// we must emit a check that v is non-nil.
// We use: typeassert v.(I).
emitTypeAssert(fn, v, rt, token.NoPos)
}
c := &MakeClosure{
Fn: makeBound(fn.Prog, obj),
Bindings: []Value{v},
}
c.setPos(e.Sel.Pos())
c.setType(tv.Type)
return fn.emit(c)
case types.FieldVal:
indices := sel.Index()
last := len(indices) - 1
v := b.expr(fn, e.X)
v = emitImplicitSelections(fn, v, indices[:last])
v = emitFieldSelection(fn, v, indices[last], false, e.Sel)
return v
}
panic("unexpected expression-relative selector")
case *ast.IndexExpr:
switch t := fn.Pkg.typeOf(e.X).Underlying().(type) {
case *types.Array:
// Non-addressable array (in a register).
v := &Index{
X: b.expr(fn, e.X),
Index: emitConv(fn, b.expr(fn, e.Index), tInt),
}
v.setPos(e.Lbrack)
v.setType(t.Elem())
return fn.emit(v)
case *types.Map:
// Maps are not addressable.
mapt := fn.Pkg.typeOf(e.X).Underlying().(*types.Map)
v := &Lookup{
X: b.expr(fn, e.X),
Index: emitConv(fn, b.expr(fn, e.Index), mapt.Key()),
}
v.setPos(e.Lbrack)
v.setType(mapt.Elem())
return fn.emit(v)
case *types.Basic: // => string
// Strings are not addressable.
v := &Lookup{
X: b.expr(fn, e.X),
Index: b.expr(fn, e.Index),
}
v.setPos(e.Lbrack)
v.setType(tByte)
return fn.emit(v)
case *types.Slice, *types.Pointer: // *array
// Addressable slice/array; use IndexAddr and Load.
return b.addr(fn, e, false).load(fn)
default:
panic("unexpected container type in IndexExpr: " + t.String())
}
case *ast.CompositeLit, *ast.StarExpr:
// Addressable types (lvalues)
return b.addr(fn, e, false).load(fn)
}
panic(fmt.Sprintf("unexpected expr: %T", e))
}
// stmtList emits to fn code for all statements in list.
func (b *builder) stmtList(fn *Function, list []ast.Stmt) {
for _, s := range list {
b.stmt(fn, s)
}
}
// receiver emits to fn code for expression e in the "receiver"
// position of selection e.f (where f may be a field or a method) and
// returns the effective receiver after applying the implicit field
// selections of sel.
//
// wantAddr requests that the result is an an address. If
// !sel.Indirect(), this may require that e be built in addr() mode; it
// must thus be addressable.
//
// escaping is defined as per builder.addr().
//
func (b *builder) receiver(fn *Function, e ast.Expr, wantAddr, escaping bool, sel *types.Selection) Value {
var v Value
if wantAddr && !sel.Indirect() && !isPointer(fn.Pkg.typeOf(e)) {
v = b.addr(fn, e, escaping).address(fn)
} else {
v = b.expr(fn, e)
}
last := len(sel.Index()) - 1
v = emitImplicitSelections(fn, v, sel.Index()[:last])
if !wantAddr && isPointer(v.Type()) {
v = emitLoad(fn, v)
}
return v
}
// setCallFunc populates the function parts of a CallCommon structure
// (Func, Method, Recv, Args[0]) based on the kind of invocation
// occurring in e.
//
func (b *builder) setCallFunc(fn *Function, e *ast.CallExpr, c *CallCommon) {
c.pos = e.Lparen
// Is this a method call?
if selector, ok := unparen(e.Fun).(*ast.SelectorExpr); ok {
sel, ok := fn.Pkg.info.Selections[selector]
if ok && sel.Kind() == types.MethodVal {
obj := sel.Obj().(*types.Func)
recv := recvType(obj)
wantAddr := isPointer(recv)
escaping := true
v := b.receiver(fn, selector.X, wantAddr, escaping, sel)
if isInterface(recv) {
// Invoke-mode call.
c.Value = v
c.Method = obj
} else {
// "Call"-mode call.
c.Value = fn.Prog.declaredFunc(obj)
c.Args = append(c.Args, v)
}
return
}
// sel.Kind()==MethodExpr indicates T.f() or (*T).f():
// a statically dispatched call to the method f in the
// method-set of T or *T. T may be an interface.
//
// e.Fun would evaluate to a concrete method, interface
// wrapper function, or promotion wrapper.
//
// For now, we evaluate it in the usual way.
//
// TODO(adonovan): opt: inline expr() here, to make the
// call static and to avoid generation of wrappers.
// It's somewhat tricky as it may consume the first
// actual parameter if the call is "invoke" mode.
//
// Examples:
// type T struct{}; func (T) f() {} // "call" mode
// type T interface { f() } // "invoke" mode
//
// type S struct{ T }
//
// var s S
// S.f(s)
// (*S).f(&s)
//
// Suggested approach:
// - consume the first actual parameter expression
// and build it with b.expr().
// - apply implicit field selections.
// - use MethodVal logic to populate fields of c.
}
// Evaluate the function operand in the usual way.
c.Value = b.expr(fn, e.Fun)
}
// emitCallArgs emits to f code for the actual parameters of call e to
// a (possibly built-in) function of effective type sig.
// The argument values are appended to args, which is then returned.
//
func (b *builder) emitCallArgs(fn *Function, sig *types.Signature, e *ast.CallExpr, args []Value) []Value {
// f(x, y, z...): pass slice z straight through.
if e.Ellipsis != 0 {
for i, arg := range e.Args {
v := emitConv(fn, b.expr(fn, arg), sig.Params().At(i).Type())
args = append(args, v)
}
return args
}
offset := len(args) // 1 if call has receiver, 0 otherwise
// Evaluate actual parameter expressions.
//
// If this is a chained call of the form f(g()) where g has
// multiple return values (MRV), they are flattened out into
// args; a suffix of them may end up in a varargs slice.
for _, arg := range e.Args {
v := b.expr(fn, arg)
if ttuple, ok := v.Type().(*types.Tuple); ok { // MRV chain
for i, n := 0, ttuple.Len(); i < n; i++ {
args = append(args, emitExtract(fn, v, i))
}
} else {
args = append(args, v)
}
}
// Actual->formal assignability conversions for normal parameters.
np := sig.Params().Len() // number of normal parameters
if sig.Variadic() {
np--
}
for i := 0; i < np; i++ {
args[offset+i] = emitConv(fn, args[offset+i], sig.Params().At(i).Type())
}
// Actual->formal assignability conversions for variadic parameter,
// and construction of slice.
if sig.Variadic() {
varargs := args[offset+np:]
st := sig.Params().At(np).Type().(*types.Slice)
vt := st.Elem()
if len(varargs) == 0 {
args = append(args, nilConst(st))
} else {
// Replace a suffix of args with a slice containing it.
at := types.NewArray(vt, int64(len(varargs)))
a := emitNew(fn, at, token.NoPos)
a.setPos(e.Rparen)
a.Comment = "varargs"
for i, arg := range varargs {
iaddr := &IndexAddr{
X: a,
Index: intConst(int64(i)),
}
iaddr.setType(types.NewPointer(vt))
fn.emit(iaddr)
emitStore(fn, iaddr, arg, arg.Pos())
}
s := &Slice{X: a}
s.setType(st)
args[offset+np] = fn.emit(s)
args = args[:offset+np+1]
}
}
return args
}
// setCall emits to fn code to evaluate all the parameters of a function
// call e, and populates *c with those values.
//
func (b *builder) setCall(fn *Function, e *ast.CallExpr, c *CallCommon) {
// First deal with the f(...) part and optional receiver.
b.setCallFunc(fn, e, c)
// Then append the other actual parameters.
sig, _ := fn.Pkg.typeOf(e.Fun).Underlying().(*types.Signature)
if sig == nil {
panic(fmt.Sprintf("no signature for call of %s", e.Fun))
}
c.Args = b.emitCallArgs(fn, sig, e, c.Args)
}
// assignOp emits to fn code to perform loc += incr or loc -= incr.
func (b *builder) assignOp(fn *Function, loc lvalue, incr Value, op token.Token, pos token.Pos) {
oldv := loc.load(fn)
loc.store(fn, emitArith(fn, op, oldv, emitConv(fn, incr, oldv.Type()), loc.typ(), pos))
}
// localValueSpec emits to fn code to define all of the vars in the
// function-local ValueSpec, spec.
//
func (b *builder) localValueSpec(fn *Function, spec *ast.ValueSpec) {
switch {
case len(spec.Values) == len(spec.Names):
// e.g. var x, y = 0, 1
// 1:1 assignment
for i, id := range spec.Names {
if !isBlankIdent(id) {
fn.addLocalForIdent(id)
}
lval := b.addr(fn, id, false) // non-escaping
b.assign(fn, lval, spec.Values[i], true, nil)
}
case len(spec.Values) == 0:
// e.g. var x, y int
// Locals are implicitly zero-initialized.
for _, id := range spec.Names {
if !isBlankIdent(id) {
lhs := fn.addLocalForIdent(id)
if fn.debugInfo() {
emitDebugRef(fn, id, lhs, true)
}
}
}
default:
// e.g. var x, y = pos()
tuple := b.exprN(fn, spec.Values[0])
for i, id := range spec.Names {
if !isBlankIdent(id) {
fn.addLocalForIdent(id)
lhs := b.addr(fn, id, false) // non-escaping
lhs.store(fn, emitExtract(fn, tuple, i))
}
}
}
}
// assignStmt emits code to fn for a parallel assignment of rhss to lhss.
// isDef is true if this is a short variable declaration (:=).
//
// Note the similarity with localValueSpec.
//
func (b *builder) assignStmt(fn *Function, lhss, rhss []ast.Expr, isDef bool) {
// Side effects of all LHSs and RHSs must occur in left-to-right order.
lvals := make([]lvalue, len(lhss))
isZero := make([]bool, len(lhss))
for i, lhs := range lhss {
var lval lvalue = blank{}
if !isBlankIdent(lhs) {
if isDef {
if obj := fn.Pkg.info.Defs[lhs.(*ast.Ident)]; obj != nil {
fn.addNamedLocal(obj)
isZero[i] = true
}
}
lval = b.addr(fn, lhs, false) // non-escaping
}
lvals[i] = lval
}
if len(lhss) == len(rhss) {
// Simple assignment: x = f() (!isDef)
// Parallel assignment: x, y = f(), g() (!isDef)
// or short var decl: x, y := f(), g() (isDef)
//
// In all cases, the RHSs may refer to the LHSs,
// so we need a storebuf.
var sb storebuf
for i := range rhss {
b.assign(fn, lvals[i], rhss[i], isZero[i], &sb)
}
sb.emit(fn)
} else {
// e.g. x, y = pos()
tuple := b.exprN(fn, rhss[0])
emitDebugRef(fn, rhss[0], tuple, false)
for i, lval := range lvals {
lval.store(fn, emitExtract(fn, tuple, i))
}
}
}
// arrayLen returns the length of the array whose composite literal elements are elts.
func (b *builder) arrayLen(fn *Function, elts []ast.Expr) int64 {
var max int64 = -1
var i int64 = -1
for _, e := range elts {
if kv, ok := e.(*ast.KeyValueExpr); ok {
i = b.expr(fn, kv.Key).(*Const).Int64()
} else {
i++
}
if i > max {
max = i
}
}
return max + 1
}
// compLit emits to fn code to initialize a composite literal e at
// address addr with type typ.
//
// Nested composite literals are recursively initialized in place
// where possible. If isZero is true, compLit assumes that addr
// holds the zero value for typ.
//
// Because the elements of a composite literal may refer to the
// variables being updated, as in the second line below,
// x := T{a: 1}
// x = T{a: x.a}
// all the reads must occur before all the writes. Thus all stores to
// loc are emitted to the storebuf sb for later execution.
//
// A CompositeLit may have pointer type only in the recursive (nested)
// case when the type name is implicit. e.g. in []*T{{}}, the inner
// literal has type *T behaves like &T{}.
// In that case, addr must hold a T, not a *T.
//
func (b *builder) compLit(fn *Function, addr Value, e *ast.CompositeLit, isZero bool, sb *storebuf) {
typ := deref(fn.Pkg.typeOf(e))
switch t := typ.Underlying().(type) {
case *types.Struct:
if !isZero && len(e.Elts) != t.NumFields() {
// memclear
sb.store(&address{addr, e.Lbrace, nil},
zeroValue(fn, deref(addr.Type())))
isZero = true
}
for i, e := range e.Elts {
fieldIndex := i
pos := e.Pos()
if kv, ok := e.(*ast.KeyValueExpr); ok {
fname := kv.Key.(*ast.Ident).Name
for i, n := 0, t.NumFields(); i < n; i++ {
sf := t.Field(i)
if sf.Name() == fname {
fieldIndex = i
pos = kv.Colon
e = kv.Value
break
}
}
}
sf := t.Field(fieldIndex)
faddr := &FieldAddr{
X: addr,
Field: fieldIndex,
}
faddr.setType(types.NewPointer(sf.Type()))
fn.emit(faddr)
b.assign(fn, &address{addr: faddr, pos: pos, expr: e}, e, isZero, sb)
}
case *types.Array, *types.Slice:
var at *types.Array
var array Value
switch t := t.(type) {
case *types.Slice:
at = types.NewArray(t.Elem(), b.arrayLen(fn, e.Elts))
alloc := emitNew(fn, at, e.Lbrace)
alloc.Comment = "slicelit"
array = alloc
case *types.Array:
at = t
array = addr
if !isZero && int64(len(e.Elts)) != at.Len() {
// memclear
sb.store(&address{array, e.Lbrace, nil},
zeroValue(fn, deref(array.Type())))
}
}
var idx *Const
for _, e := range e.Elts {
pos := e.Pos()
if kv, ok := e.(*ast.KeyValueExpr); ok {
idx = b.expr(fn, kv.Key).(*Const)
pos = kv.Colon
e = kv.Value
} else {
var idxval int64
if idx != nil {
idxval = idx.Int64() + 1
}
idx = intConst(idxval)
}
iaddr := &IndexAddr{
X: array,
Index: idx,
}
iaddr.setType(types.NewPointer(at.Elem()))
fn.emit(iaddr)
if t != at { // slice
// backing array is unaliased => storebuf not needed.
b.assign(fn, &address{addr: iaddr, pos: pos, expr: e}, e, true, nil)
} else {
b.assign(fn, &address{addr: iaddr, pos: pos, expr: e}, e, true, sb)
}
}
if t != at { // slice
s := &Slice{X: array}
s.setPos(e.Lbrace)
s.setType(typ)
sb.store(&address{addr: addr, pos: e.Lbrace, expr: e}, fn.emit(s))
}
case *types.Map:
m := &MakeMap{Reserve: intConst(int64(len(e.Elts)))}
m.setPos(e.Lbrace)
m.setType(typ)
fn.emit(m)
for _, e := range e.Elts {
e := e.(*ast.KeyValueExpr)
// If a key expression in a map literal is itself a
// composite literal, the type may be omitted.
// For example:
// map[*struct{}]bool{{}: true}
// An &-operation may be implied:
// map[*struct{}]bool{&struct{}{}: true}
var key Value
if _, ok := unparen(e.Key).(*ast.CompositeLit); ok && isPointer(t.Key()) {
// A CompositeLit never evaluates to a pointer,
// so if the type of the location is a pointer,
// an &-operation is implied.
key = b.addr(fn, e.Key, true).address(fn)
} else {
key = b.expr(fn, e.Key)
}
loc := element{
m: m,
k: emitConv(fn, key, t.Key()),
t: t.Elem(),
pos: e.Colon,
}
// We call assign() only because it takes care
// of any &-operation required in the recursive
// case, e.g.,
// map[int]*struct{}{0: {}} implies &struct{}{}.
// In-place update is of course impossible,
// and no storebuf is needed.
b.assign(fn, &loc, e.Value, true, nil)
}
sb.store(&address{addr: addr, pos: e.Lbrace, expr: e}, m)
default:
panic("unexpected CompositeLit type: " + t.String())
}
}
// switchStmt emits to fn code for the switch statement s, optionally
// labelled by label.
//
func (b *builder) switchStmt(fn *Function, s *ast.SwitchStmt, label *lblock) {
// We treat SwitchStmt like a sequential if-else chain.
// Multiway dispatch can be recovered later by ssautil.Switches()
// to those cases that are free of side effects.
if s.Init != nil {
b.stmt(fn, s.Init)
}
var tag Value = vTrue
if s.Tag != nil {
tag = b.expr(fn, s.Tag)
}
done := fn.newBasicBlock("switch.done")
if label != nil {
label._break = done
}
// We pull the default case (if present) down to the end.
// But each fallthrough label must point to the next
// body block in source order, so we preallocate a
// body block (fallthru) for the next case.
// Unfortunately this makes for a confusing block order.
var dfltBody *[]ast.Stmt
var dfltFallthrough *BasicBlock
var fallthru, dfltBlock *BasicBlock
ncases := len(s.Body.List)
for i, clause := range s.Body.List {
body := fallthru
if body == nil {
body = fn.newBasicBlock("switch.body") // first case only
}
// Preallocate body block for the next case.
fallthru = done
if i+1 < ncases {
fallthru = fn.newBasicBlock("switch.body")
}
cc := clause.(*ast.CaseClause)
if cc.List == nil {
// Default case.
dfltBody = &cc.Body
dfltFallthrough = fallthru
dfltBlock = body
continue
}
var nextCond *BasicBlock
for _, cond := range cc.List {
nextCond = fn.newBasicBlock("switch.next")
// TODO(adonovan): opt: when tag==vTrue, we'd
// get better code if we use b.cond(cond)
// instead of BinOp(EQL, tag, b.expr(cond))
// followed by If. Don't forget conversions
// though.
cond := emitCompare(fn, token.EQL, tag, b.expr(fn, cond), cond.Pos())
emitIf(fn, cond, body, nextCond)
fn.currentBlock = nextCond
}
fn.currentBlock = body
fn.targets = &targets{
tail: fn.targets,
_break: done,
_fallthrough: fallthru,
}
b.stmtList(fn, cc.Body)
fn.targets = fn.targets.tail
emitJump(fn, done)
fn.currentBlock = nextCond
}
if dfltBlock != nil {
emitJump(fn, dfltBlock)
fn.currentBlock = dfltBlock
fn.targets = &targets{
tail: fn.targets,
_break: done,
_fallthrough: dfltFallthrough,
}
b.stmtList(fn, *dfltBody)
fn.targets = fn.targets.tail
}
emitJump(fn, done)
fn.currentBlock = done
}
// typeSwitchStmt emits to fn code for the type switch statement s, optionally
// labelled by label.
//
func (b *builder) typeSwitchStmt(fn *Function, s *ast.TypeSwitchStmt, label *lblock) {
// We treat TypeSwitchStmt like a sequential if-else chain.
// Multiway dispatch can be recovered later by ssautil.Switches().
// Typeswitch lowering:
//
// var x X
// switch y := x.(type) {
// case T1, T2: S1 // >1 (y := x)
// case nil: SN // nil (y := x)
// default: SD // 0 types (y := x)
// case T3: S3 // 1 type (y := x.(T3))
// }
//
// ...s.Init...
// x := eval x
// .caseT1:
// t1, ok1 := typeswitch,ok x <T1>
// if ok1 then goto S1 else goto .caseT2
// .caseT2:
// t2, ok2 := typeswitch,ok x <T2>
// if ok2 then goto S1 else goto .caseNil
// .S1:
// y := x
// ...S1...
// goto done
// .caseNil:
// if t2, ok2 := typeswitch,ok x <T2>
// if x == nil then goto SN else goto .caseT3
// .SN:
// y := x
// ...SN...
// goto done
// .caseT3:
// t3, ok3 := typeswitch,ok x <T3>
// if ok3 then goto S3 else goto default
// .S3:
// y := t3
// ...S3...
// goto done
// .default:
// y := x
// ...SD...
// goto done
// .done:
if s.Init != nil {
b.stmt(fn, s.Init)
}
var x Value
switch ass := s.Assign.(type) {
case *ast.ExprStmt: // x.(type)
x = b.expr(fn, unparen(ass.X).(*ast.TypeAssertExpr).X)
case *ast.AssignStmt: // y := x.(type)
x = b.expr(fn, unparen(ass.Rhs[0]).(*ast.TypeAssertExpr).X)
}
done := fn.newBasicBlock("typeswitch.done")
if label != nil {
label._break = done
}
var default_ *ast.CaseClause
for _, clause := range s.Body.List {
cc := clause.(*ast.CaseClause)
if cc.List == nil {
default_ = cc
continue
}
body := fn.newBasicBlock("typeswitch.body")
var next *BasicBlock
var casetype types.Type
var ti Value // ti, ok := typeassert,ok x <Ti>
for _, cond := range cc.List {
next = fn.newBasicBlock("typeswitch.next")
casetype = fn.Pkg.typeOf(cond)
var condv Value
if casetype == tUntypedNil {
condv = emitCompare(fn, token.EQL, x, nilConst(x.Type()), token.NoPos)
ti = x
} else {
yok := emitTypeTest(fn, x, casetype, cc.Case)
ti = emitExtract(fn, yok, 0)
condv = emitExtract(fn, yok, 1)
}
emitIf(fn, condv, body, next)
fn.currentBlock = next
}
if len(cc.List) != 1 {
ti = x
}
fn.currentBlock = body
b.typeCaseBody(fn, cc, ti, done)
fn.currentBlock = next
}
if default_ != nil {
b.typeCaseBody(fn, default_, x, done)
} else {
emitJump(fn, done)
}
fn.currentBlock = done
}
func (b *builder) typeCaseBody(fn *Function, cc *ast.CaseClause, x Value, done *BasicBlock) {
if obj := fn.Pkg.info.Implicits[cc]; obj != nil {
// In a switch y := x.(type), each case clause
// implicitly declares a distinct object y.
// In a single-type case, y has that type.
// In multi-type cases, 'case nil' and default,
// y has the same type as the interface operand.
emitStore(fn, fn.addNamedLocal(obj), x, obj.Pos())
}
fn.targets = &targets{
tail: fn.targets,
_break: done,
}
b.stmtList(fn, cc.Body)
fn.targets = fn.targets.tail
emitJump(fn, done)
}
// selectStmt emits to fn code for the select statement s, optionally
// labelled by label.
//
func (b *builder) selectStmt(fn *Function, s *ast.SelectStmt, label *lblock) {
// A blocking select of a single case degenerates to a
// simple send or receive.
// TODO(adonovan): opt: is this optimization worth its weight?
if len(s.Body.List) == 1 {
clause := s.Body.List[0].(*ast.CommClause)
if clause.Comm != nil {
b.stmt(fn, clause.Comm)
done := fn.newBasicBlock("select.done")
if label != nil {
label._break = done
}
fn.targets = &targets{
tail: fn.targets,
_break: done,
}
b.stmtList(fn, clause.Body)
fn.targets = fn.targets.tail
emitJump(fn, done)
fn.currentBlock = done
return
}
}
// First evaluate all channels in all cases, and find
// the directions of each state.
var states []*SelectState
blocking := true
debugInfo := fn.debugInfo()
for _, clause := range s.Body.List {
var st *SelectState
switch comm := clause.(*ast.CommClause).Comm.(type) {
case nil: // default case
blocking = false
continue
case *ast.SendStmt: // ch<- i
ch := b.expr(fn, comm.Chan)
st = &SelectState{
Dir: types.SendOnly,
Chan: ch,
Send: emitConv(fn, b.expr(fn, comm.Value),
ch.Type().Underlying().(*types.Chan).Elem()),
Pos: comm.Arrow,
}
if debugInfo {
st.DebugNode = comm
}
case *ast.AssignStmt: // x := <-ch
recv := unparen(comm.Rhs[0]).(*ast.UnaryExpr)
st = &SelectState{
Dir: types.RecvOnly,
Chan: b.expr(fn, recv.X),
Pos: recv.OpPos,
}
if debugInfo {
st.DebugNode = recv
}
case *ast.ExprStmt: // <-ch
recv := unparen(comm.X).(*ast.UnaryExpr)
st = &SelectState{
Dir: types.RecvOnly,
Chan: b.expr(fn, recv.X),
Pos: recv.OpPos,
}
if debugInfo {
st.DebugNode = recv
}
}
states = append(states, st)
}
// We dispatch on the (fair) result of Select using a
// sequential if-else chain, in effect:
//
// idx, recvOk, r0...r_n-1 := select(...)
// if idx == 0 { // receive on channel 0 (first receive => r0)
// x, ok := r0, recvOk
// ...state0...
// } else if v == 1 { // send on channel 1
// ...state1...
// } else {
// ...default...
// }
sel := &Select{
States: states,
Blocking: blocking,
}
sel.setPos(s.Select)
var vars []*types.Var
vars = append(vars, varIndex, varOk)
for _, st := range states {
if st.Dir == types.RecvOnly {
tElem := st.Chan.Type().Underlying().(*types.Chan).Elem()
vars = append(vars, anonVar(tElem))
}
}
sel.setType(types.NewTuple(vars...))
fn.emit(sel)
idx := emitExtract(fn, sel, 0)
done := fn.newBasicBlock("select.done")
if label != nil {
label._break = done
}
var defaultBody *[]ast.Stmt
state := 0
r := 2 // index in 'sel' tuple of value; increments if st.Dir==RECV
for _, cc := range s.Body.List {
clause := cc.(*ast.CommClause)
if clause.Comm == nil {
defaultBody = &clause.Body
continue
}
body := fn.newBasicBlock("select.body")
next := fn.newBasicBlock("select.next")
emitIf(fn, emitCompare(fn, token.EQL, idx, intConst(int64(state)), token.NoPos), body, next)
fn.currentBlock = body
fn.targets = &targets{
tail: fn.targets,
_break: done,
}
switch comm := clause.Comm.(type) {
case *ast.ExprStmt: // <-ch
if debugInfo {
v := emitExtract(fn, sel, r)
emitDebugRef(fn, states[state].DebugNode.(ast.Expr), v, false)
}
r++
case *ast.AssignStmt: // x := <-states[state].Chan
if comm.Tok == token.DEFINE {
fn.addLocalForIdent(comm.Lhs[0].(*ast.Ident))
}
x := b.addr(fn, comm.Lhs[0], false) // non-escaping
v := emitExtract(fn, sel, r)
if debugInfo {
emitDebugRef(fn, states[state].DebugNode.(ast.Expr), v, false)
}
x.store(fn, v)
if len(comm.Lhs) == 2 { // x, ok := ...
if comm.Tok == token.DEFINE {
fn.addLocalForIdent(comm.Lhs[1].(*ast.Ident))
}
ok := b.addr(fn, comm.Lhs[1], false) // non-escaping
ok.store(fn, emitExtract(fn, sel, 1))
}
r++
}
b.stmtList(fn, clause.Body)
fn.targets = fn.targets.tail
emitJump(fn, done)
fn.currentBlock = next
state++
}
if defaultBody != nil {
fn.targets = &targets{
tail: fn.targets,
_break: done,
}
b.stmtList(fn, *defaultBody)
fn.targets = fn.targets.tail
} else {
// A blocking select must match some case.
// (This should really be a runtime.errorString, not a string.)
fn.emit(&Panic{
X: emitConv(fn, stringConst("blocking select matched no case"), tEface),
})
fn.currentBlock = fn.newBasicBlock("unreachable")
}
emitJump(fn, done)
fn.currentBlock = done
}
// forStmt emits to fn code for the for statement s, optionally
// labelled by label.
//
func (b *builder) forStmt(fn *Function, s *ast.ForStmt, label *lblock) {
// ...init...
// jump loop
// loop:
// if cond goto body else done
// body:
// ...body...
// jump post
// post: (target of continue)
// ...post...
// jump loop
// done: (target of break)
if s.Init != nil {
b.stmt(fn, s.Init)
}
body := fn.newBasicBlock("for.body")
done := fn.newBasicBlock("for.done") // target of 'break'
loop := body // target of back-edge
if s.Cond != nil {
loop = fn.newBasicBlock("for.loop")
}
cont := loop // target of 'continue'
if s.Post != nil {
cont = fn.newBasicBlock("for.post")
}
if label != nil {
label._break = done
label._continue = cont
}
emitJump(fn, loop)
fn.currentBlock = loop
if loop != body {
b.cond(fn, s.Cond, body, done)
fn.currentBlock = body
}
fn.targets = &targets{
tail: fn.targets,
_break: done,
_continue: cont,
}
b.stmt(fn, s.Body)
fn.targets = fn.targets.tail
emitJump(fn, cont)
if s.Post != nil {
fn.currentBlock = cont
b.stmt(fn, s.Post)
emitJump(fn, loop) // back-edge
}
fn.currentBlock = done
}
// rangeIndexed emits to fn the header for an integer-indexed loop
// over array, *array or slice value x.
// The v result is defined only if tv is non-nil.
// forPos is the position of the "for" token.
//
func (b *builder) rangeIndexed(fn *Function, x Value, tv types.Type, pos token.Pos) (k, v Value, loop, done *BasicBlock) {
//
// length = len(x)
// index = -1
// loop: (target of continue)
// index++
// if index < length goto body else done
// body:
// k = index
// v = x[index]
// ...body...
// jump loop
// done: (target of break)
// Determine number of iterations.
var length Value
if arr, ok := deref(x.Type()).Underlying().(*types.Array); ok {
// For array or *array, the number of iterations is
// known statically thanks to the type. We avoid a
// data dependence upon x, permitting later dead-code
// elimination if x is pure, static unrolling, etc.
// Ranging over a nil *array may have >0 iterations.
// We still generate code for x, in case it has effects.
length = intConst(arr.Len())
} else {
// length = len(x).
var c Call
c.Call.Value = makeLen(x.Type())
c.Call.Args = []Value{x}
c.setType(tInt)
length = fn.emit(&c)
}
index := fn.addLocal(tInt, token.NoPos)
emitStore(fn, index, intConst(-1), pos)
loop = fn.newBasicBlock("rangeindex.loop")
emitJump(fn, loop)
fn.currentBlock = loop
incr := &BinOp{
Op: token.ADD,
X: emitLoad(fn, index),
Y: vOne,
}
incr.setType(tInt)
emitStore(fn, index, fn.emit(incr), pos)
body := fn.newBasicBlock("rangeindex.body")
done = fn.newBasicBlock("rangeindex.done")
emitIf(fn, emitCompare(fn, token.LSS, incr, length, token.NoPos), body, done)
fn.currentBlock = body
k = emitLoad(fn, index)
if tv != nil {
switch t := x.Type().Underlying().(type) {
case *types.Array:
instr := &Index{
X: x,
Index: k,
}
instr.setType(t.Elem())
v = fn.emit(instr)
case *types.Pointer: // *array
instr := &IndexAddr{
X: x,
Index: k,
}
instr.setType(types.NewPointer(t.Elem().Underlying().(*types.Array).Elem()))
v = emitLoad(fn, fn.emit(instr))
case *types.Slice:
instr := &IndexAddr{
X: x,
Index: k,
}
instr.setType(types.NewPointer(t.Elem()))
v = emitLoad(fn, fn.emit(instr))
default:
panic("rangeIndexed x:" + t.String())
}
}
return
}
// rangeIter emits to fn the header for a loop using
// Range/Next/Extract to iterate over map or string value x.
// tk and tv are the types of the key/value results k and v, or nil
// if the respective component is not wanted.
//
func (b *builder) rangeIter(fn *Function, x Value, tk, tv types.Type, pos token.Pos) (k, v Value, loop, done *BasicBlock) {
//
// it = range x
// loop: (target of continue)
// okv = next it (ok, key, value)
// ok = extract okv #0
// if ok goto body else done
// body:
// k = extract okv #1
// v = extract okv #2
// ...body...
// jump loop
// done: (target of break)
//
if tk == nil {
tk = tInvalid
}
if tv == nil {
tv = tInvalid
}
rng := &Range{X: x}
rng.setPos(pos)
rng.setType(tRangeIter)
it := fn.emit(rng)
loop = fn.newBasicBlock("rangeiter.loop")
emitJump(fn, loop)
fn.currentBlock = loop
_, isString := x.Type().Underlying().(*types.Basic)
okv := &Next{
Iter: it,
IsString: isString,
}
okv.setType(types.NewTuple(
varOk,
newVar("k", tk),
newVar("v", tv),
))
fn.emit(okv)
body := fn.newBasicBlock("rangeiter.body")
done = fn.newBasicBlock("rangeiter.done")
emitIf(fn, emitExtract(fn, okv, 0), body, done)
fn.currentBlock = body
if tk != tInvalid {
k = emitExtract(fn, okv, 1)
}
if tv != tInvalid {
v = emitExtract(fn, okv, 2)
}
return
}
// rangeChan emits to fn the header for a loop that receives from
// channel x until it fails.
// tk is the channel's element type, or nil if the k result is
// not wanted
// pos is the position of the '=' or ':=' token.
//
func (b *builder) rangeChan(fn *Function, x Value, tk types.Type, pos token.Pos) (k Value, loop, done *BasicBlock) {
//
// loop: (target of continue)
// ko = <-x (key, ok)
// ok = extract ko #1
// if ok goto body else done
// body:
// k = extract ko #0
// ...
// goto loop
// done: (target of break)
loop = fn.newBasicBlock("rangechan.loop")
emitJump(fn, loop)
fn.currentBlock = loop
recv := &UnOp{
Op: token.ARROW,
X: x,
CommaOk: true,
}
recv.setPos(pos)
recv.setType(types.NewTuple(
newVar("k", x.Type().Underlying().(*types.Chan).Elem()),
varOk,
))
ko := fn.emit(recv)
body := fn.newBasicBlock("rangechan.body")
done = fn.newBasicBlock("rangechan.done")
emitIf(fn, emitExtract(fn, ko, 1), body, done)
fn.currentBlock = body
if tk != nil {
k = emitExtract(fn, ko, 0)
}
return
}
// rangeStmt emits to fn code for the range statement s, optionally
// labelled by label.
//
func (b *builder) rangeStmt(fn *Function, s *ast.RangeStmt, label *lblock) {
var tk, tv types.Type
if s.Key != nil && !isBlankIdent(s.Key) {
tk = fn.Pkg.typeOf(s.Key)
}
if s.Value != nil && !isBlankIdent(s.Value) {
tv = fn.Pkg.typeOf(s.Value)
}
// If iteration variables are defined (:=), this
// occurs once outside the loop.
//
// Unlike a short variable declaration, a RangeStmt
// using := never redeclares an existing variable; it
// always creates a new one.
if s.Tok == token.DEFINE {
if tk != nil {
fn.addLocalForIdent(s.Key.(*ast.Ident))
}
if tv != nil {
fn.addLocalForIdent(s.Value.(*ast.Ident))
}
}
x := b.expr(fn, s.X)
var k, v Value
var loop, done *BasicBlock
switch rt := x.Type().Underlying().(type) {
case *types.Slice, *types.Array, *types.Pointer: // *array
k, v, loop, done = b.rangeIndexed(fn, x, tv, s.For)
case *types.Chan:
k, loop, done = b.rangeChan(fn, x, tk, s.For)
case *types.Map, *types.Basic: // string
k, v, loop, done = b.rangeIter(fn, x, tk, tv, s.For)
default:
panic("Cannot range over: " + rt.String())
}
// Evaluate both LHS expressions before we update either.
var kl, vl lvalue
if tk != nil {
kl = b.addr(fn, s.Key, false) // non-escaping
}
if tv != nil {
vl = b.addr(fn, s.Value, false) // non-escaping
}
if tk != nil {
kl.store(fn, k)
}
if tv != nil {
vl.store(fn, v)
}
if label != nil {
label._break = done
label._continue = loop
}
fn.targets = &targets{
tail: fn.targets,
_break: done,
_continue: loop,
}
b.stmt(fn, s.Body)
fn.targets = fn.targets.tail
emitJump(fn, loop) // back-edge
fn.currentBlock = done
}
// stmt lowers statement s to SSA form, emitting code to fn.
func (b *builder) stmt(fn *Function, _s ast.Stmt) {
// The label of the current statement. If non-nil, its _goto
// target is always set; its _break and _continue are set only
// within the body of switch/typeswitch/select/for/range.
// It is effectively an additional default-nil parameter of stmt().
var label *lblock
start:
switch s := _s.(type) {
case *ast.EmptyStmt:
// ignore. (Usually removed by gofmt.)
case *ast.DeclStmt: // Con, Var or Typ
d := s.Decl.(*ast.GenDecl)
if d.Tok == token.VAR {
for _, spec := range d.Specs {
if vs, ok := spec.(*ast.ValueSpec); ok {
b.localValueSpec(fn, vs)
}
}
}
case *ast.LabeledStmt:
label = fn.labelledBlock(s.Label)
emitJump(fn, label._goto)
fn.currentBlock = label._goto
_s = s.Stmt
goto start // effectively: tailcall stmt(fn, s.Stmt, label)
case *ast.ExprStmt:
b.expr(fn, s.X)
case *ast.SendStmt:
fn.emit(&Send{
Chan: b.expr(fn, s.Chan),
X: emitConv(fn, b.expr(fn, s.Value),
fn.Pkg.typeOf(s.Chan).Underlying().(*types.Chan).Elem()),
pos: s.Arrow,
})
case *ast.IncDecStmt:
op := token.ADD
if s.Tok == token.DEC {
op = token.SUB
}
loc := b.addr(fn, s.X, false)
b.assignOp(fn, loc, NewConst(exact.MakeInt64(1), loc.typ()), op, s.Pos())
case *ast.AssignStmt:
switch s.Tok {
case token.ASSIGN, token.DEFINE:
b.assignStmt(fn, s.Lhs, s.Rhs, s.Tok == token.DEFINE)
default: // +=, etc.
op := s.Tok + token.ADD - token.ADD_ASSIGN
b.assignOp(fn, b.addr(fn, s.Lhs[0], false), b.expr(fn, s.Rhs[0]), op, s.Pos())
}
case *ast.GoStmt:
// The "intrinsics" new/make/len/cap are forbidden here.
// panic is treated like an ordinary function call.
v := Go{pos: s.Go}
b.setCall(fn, s.Call, &v.Call)
fn.emit(&v)
case *ast.DeferStmt:
// The "intrinsics" new/make/len/cap are forbidden here.
// panic is treated like an ordinary function call.
v := Defer{pos: s.Defer}
b.setCall(fn, s.Call, &v.Call)
fn.emit(&v)
// A deferred call can cause recovery from panic,
// and control resumes at the Recover block.
createRecoverBlock(fn)
case *ast.ReturnStmt:
var results []Value
if len(s.Results) == 1 && fn.Signature.Results().Len() > 1 {
// Return of one expression in a multi-valued function.
tuple := b.exprN(fn, s.Results[0])
ttuple := tuple.Type().(*types.Tuple)
for i, n := 0, ttuple.Len(); i < n; i++ {
results = append(results,
emitConv(fn, emitExtract(fn, tuple, i),
fn.Signature.Results().At(i).Type()))
}
} else {
// 1:1 return, or no-arg return in non-void function.
for i, r := range s.Results {
v := emitConv(fn, b.expr(fn, r), fn.Signature.Results().At(i).Type())
results = append(results, v)
}
}
if fn.namedResults != nil {
// Function has named result parameters (NRPs).
// Perform parallel assignment of return operands to NRPs.
for i, r := range results {
emitStore(fn, fn.namedResults[i], r, s.Return)
}
}
// Run function calls deferred in this
// function when explicitly returning from it.
fn.emit(new(RunDefers))
if fn.namedResults != nil {
// Reload NRPs to form the result tuple.
results = results[:0]
for _, r := range fn.namedResults {
results = append(results, emitLoad(fn, r))
}
}
fn.emit(&Return{Results: results, pos: s.Return})
fn.currentBlock = fn.newBasicBlock("unreachable")
case *ast.BranchStmt:
var block *BasicBlock
switch s.Tok {
case token.BREAK:
if s.Label != nil {
block = fn.labelledBlock(s.Label)._break
} else {
for t := fn.targets; t != nil && block == nil; t = t.tail {
block = t._break
}
}
case token.CONTINUE:
if s.Label != nil {
block = fn.labelledBlock(s.Label)._continue
} else {
for t := fn.targets; t != nil && block == nil; t = t.tail {
block = t._continue
}
}
case token.FALLTHROUGH:
for t := fn.targets; t != nil && block == nil; t = t.tail {
block = t._fallthrough
}
case token.GOTO:
block = fn.labelledBlock(s.Label)._goto
}
emitJump(fn, block)
fn.currentBlock = fn.newBasicBlock("unreachable")
case *ast.BlockStmt:
b.stmtList(fn, s.List)
case *ast.IfStmt:
if s.Init != nil {
b.stmt(fn, s.Init)
}
then := fn.newBasicBlock("if.then")
done := fn.newBasicBlock("if.done")
els := done
if s.Else != nil {
els = fn.newBasicBlock("if.else")
}
b.cond(fn, s.Cond, then, els)
fn.currentBlock = then
b.stmt(fn, s.Body)
emitJump(fn, done)
if s.Else != nil {
fn.currentBlock = els
b.stmt(fn, s.Else)
emitJump(fn, done)
}
fn.currentBlock = done
case *ast.SwitchStmt:
b.switchStmt(fn, s, label)
case *ast.TypeSwitchStmt:
b.typeSwitchStmt(fn, s, label)
case *ast.SelectStmt:
b.selectStmt(fn, s, label)
case *ast.ForStmt:
b.forStmt(fn, s, label)
case *ast.RangeStmt:
b.rangeStmt(fn, s, label)
default:
panic(fmt.Sprintf("unexpected statement kind: %T", s))
}
}
// buildFunction builds SSA code for the body of function fn. Idempotent.
func (b *builder) buildFunction(fn *Function) {
if fn.Blocks != nil {
return // building already started
}
var recvField *ast.FieldList
var body *ast.BlockStmt
var functype *ast.FuncType
switch n := fn.syntax.(type) {
case nil:
return // not a Go source function. (Synthetic, or from object file.)
case *ast.FuncDecl:
functype = n.Type
recvField = n.Recv
body = n.Body
case *ast.FuncLit:
functype = n.Type
body = n.Body
default:
panic(n)
}
if body == nil {
// External function.
if fn.Params == nil {
// This condition ensures we add a non-empty
// params list once only, but we may attempt
// the degenerate empty case repeatedly.
// TODO(adonovan): opt: don't do that.
// We set Function.Params even though there is no body
// code to reference them. This simplifies clients.
if recv := fn.Signature.Recv(); recv != nil {
fn.addParamObj(recv)
}
params := fn.Signature.Params()
for i, n := 0, params.Len(); i < n; i++ {
fn.addParamObj(params.At(i))
}
}
return
}
if fn.Prog.mode&LogSource != 0 {
defer logStack("build function %s @ %s", fn, fn.Prog.Fset.Position(fn.pos))()
}
fn.startBody()
fn.createSyntacticParams(recvField, functype)
b.stmt(fn, body)
if cb := fn.currentBlock; cb != nil && (cb == fn.Blocks[0] || cb == fn.Recover || cb.Preds != nil) {
// Control fell off the end of the function's body block.
//
// Block optimizations eliminate the current block, if
// unreachable. It is a builder invariant that
// if this no-arg return is ill-typed for
// fn.Signature.Results, this block must be
// unreachable. The sanity checker checks this.
fn.emit(new(RunDefers))
fn.emit(new(Return))
}
fn.finishBody()
}
// buildFuncDecl builds SSA code for the function or method declared
// by decl in package pkg.
//
func (b *builder) buildFuncDecl(pkg *Package, decl *ast.FuncDecl) {
id := decl.Name
if isBlankIdent(id) {
return // discard
}
fn := pkg.values[pkg.info.Defs[id]].(*Function)
if decl.Recv == nil && id.Name == "init" {
var v Call
v.Call.Value = fn
v.setType(types.NewTuple())
pkg.init.emit(&v)
}
b.buildFunction(fn)
}
// Build calls Package.Build for each package in prog.
// Building occurs in parallel unless the BuildSerially mode flag was set.
//
// Build is intended for whole-program analysis; a typical compiler
// need only build a single package.
//
// Build is idempotent and thread-safe.
//
func (prog *Program) Build() {
var wg sync.WaitGroup
for _, p := range prog.packages {
if prog.mode&BuildSerially != 0 {
p.Build()
} else {
wg.Add(1)
go func(p *Package) {
p.Build()
wg.Done()
}(p)
}
}
wg.Wait()
}
// Build builds SSA code for all functions and vars in package p.
//
// Precondition: CreatePackage must have been called for all of p's
// direct imports (and hence its direct imports must have been
// error-free).
//
// Build is idempotent and thread-safe.
//
func (p *Package) Build() { p.buildOnce.Do(p.build) }
func (p *Package) build() {
if p.info == nil {
return // synthetic package, e.g. "testmain"
}
// Ensure we have runtime type info for all exported members.
// TODO(adonovan): ideally belongs in memberFromObject, but
// that would require package creation in topological order.
for name, mem := range p.Members {
if ast.IsExported(name) {
p.Prog.needMethodsOf(mem.Type())
}
}
if p.Prog.mode&LogSource != 0 {
defer logStack("build %s", p)()
}
init := p.init
init.startBody()
var done *BasicBlock
if p.Prog.mode&BareInits == 0 {
// Make init() skip if package is already initialized.
initguard := p.Var("init$guard")
doinit := init.newBasicBlock("init.start")
done = init.newBasicBlock("init.done")
emitIf(init, emitLoad(init, initguard), done, doinit)
init.currentBlock = doinit
emitStore(init, initguard, vTrue, token.NoPos)
// Call the init() function of each package we import.
for _, pkg := range p.Pkg.Imports() {
prereq := p.Prog.packages[pkg]
if prereq == nil {
panic(fmt.Sprintf("Package(%q).Build(): unsatisfied import: Program.CreatePackage(%q) was not called", p.Pkg.Path(), pkg.Path()))
}
var v Call
v.Call.Value = prereq.init
v.Call.pos = init.pos
v.setType(types.NewTuple())
init.emit(&v)
}
}
var b builder
// Initialize package-level vars in correct order.
for _, varinit := range p.info.InitOrder {
if init.Prog.mode&LogSource != 0 {
fmt.Fprintf(os.Stderr, "build global initializer %v @ %s\n",
varinit.Lhs, p.Prog.Fset.Position(varinit.Rhs.Pos()))
}
if len(varinit.Lhs) == 1 {
// 1:1 initialization: var x, y = a(), b()
var lval lvalue
if v := varinit.Lhs[0]; v.Name() != "_" {
lval = &address{addr: p.values[v].(*Global), pos: v.Pos()}
} else {
lval = blank{}
}
b.assign(init, lval, varinit.Rhs, true, nil)
} else {
// n:1 initialization: var x, y := f()
tuple := b.exprN(init, varinit.Rhs)
for i, v := range varinit.Lhs {
if v.Name() == "_" {
continue
}
emitStore(init, p.values[v].(*Global), emitExtract(init, tuple, i), v.Pos())
}
}
}
// Build all package-level functions, init functions
// and methods, including unreachable/blank ones.
// We build them in source order, but it's not significant.
for _, file := range p.files {
for _, decl := range file.Decls {
if decl, ok := decl.(*ast.FuncDecl); ok {
b.buildFuncDecl(p, decl)
}
}
}
// Finish up init().
if p.Prog.mode&BareInits == 0 {
emitJump(init, done)
init.currentBlock = done
}
init.emit(new(Return))
init.finishBody()
p.info = nil // We no longer need ASTs or go/types deductions.
if p.Prog.mode&SanityCheckFunctions != 0 {
sanityCheckPackage(p)
}
}
// Like ObjectOf, but panics instead of returning nil.
// Only valid during p's create and build phases.
func (p *Package) objectOf(id *ast.Ident) types.Object {
if o := p.info.ObjectOf(id); o != nil {
return o
}
panic(fmt.Sprintf("no types.Object for ast.Ident %s @ %s",
id.Name, p.Prog.Fset.Position(id.Pos())))
}
// Like TypeOf, but panics instead of returning nil.
// Only valid during p's create and build phases.
func (p *Package) typeOf(e ast.Expr) types.Type {
if T := p.info.TypeOf(e); T != nil {
return T
}
panic(fmt.Sprintf("no type for %T @ %s",
e, p.Prog.Fset.Position(e.Pos())))
}
|