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
|
package compiler
// This file manages symbols, that is, functions and globals. It reads their
// pragmas, determines the link name, etc.
import (
"fmt"
"go/ast"
"go/token"
"go/types"
"strconv"
"strings"
"github.com/tinygo-org/tinygo/compiler/llvmutil"
"github.com/tinygo-org/tinygo/goenv"
"github.com/tinygo-org/tinygo/loader"
"golang.org/x/tools/go/ssa"
"tinygo.org/x/go-llvm"
)
// functionInfo contains some information about a function or method. In
// particular, it contains information obtained from pragmas.
//
// The linkName value contains a valid link name, even if //go:linkname is not
// present.
type functionInfo struct {
wasmModule string // go:wasm-module
wasmName string // wasm-export-name or wasm-import-name in the IR
wasmExport string // go:wasmexport is defined (export is unset, this adds an exported wrapper)
wasmExportPos token.Pos // position of //go:wasmexport comment
linkName string // go:linkname, go:export - the IR function name
section string // go:section - object file section name
exported bool // go:export, CGo
interrupt bool // go:interrupt
nobounds bool // go:nobounds
noescape bool // go:noescape
variadic bool // go:variadic (CGo only)
inline inlineType // go:inline
}
type inlineType int
// How much to inline.
const (
// Default behavior. The compiler decides for itself whether any given
// function will be inlined. Whether any function is inlined depends on the
// optimization level.
inlineDefault inlineType = iota
// Inline hint, just like the C inline keyword (signalled using
// //go:inline). The compiler will be more likely to inline this function,
// but it is not a guarantee.
inlineHint
// Don't inline, just like the GCC noinline attribute. Signalled using
// //go:noinline.
inlineNone
)
// Values for the allockind attribute. Source:
// https://github.com/llvm/llvm-project/blob/release/16.x/llvm/include/llvm/IR/Attributes.h#L49
const (
allocKindAlloc = 1 << iota
allocKindRealloc
allocKindFree
allocKindUninitialized
allocKindZeroed
allocKindAligned
)
// getFunction returns the LLVM function for the given *ssa.Function, creating
// it if needed. It can later be filled with compilerContext.createFunction().
func (c *compilerContext) getFunction(fn *ssa.Function) (llvm.Type, llvm.Value) {
info := c.getFunctionInfo(fn)
llvmFn := c.mod.NamedFunction(info.linkName)
if !llvmFn.IsNil() {
return llvmFn.GlobalValueType(), llvmFn
}
var retType llvm.Type
if fn.Signature.Results() == nil {
retType = c.ctx.VoidType()
} else if fn.Signature.Results().Len() == 1 {
retType = c.getLLVMType(fn.Signature.Results().At(0).Type())
} else {
results := make([]llvm.Type, 0, fn.Signature.Results().Len())
for i := 0; i < fn.Signature.Results().Len(); i++ {
results = append(results, c.getLLVMType(fn.Signature.Results().At(i).Type()))
}
retType = c.ctx.StructType(results, false)
}
var paramInfos []paramInfo
for _, param := range getParams(fn.Signature) {
paramType := c.getLLVMType(param.Type())
paramFragmentInfos := c.expandFormalParamType(paramType, param.Name(), param.Type())
paramInfos = append(paramInfos, paramFragmentInfos...)
}
// Add an extra parameter as the function context. This context is used in
// closures and bound methods, but should be optimized away when not used.
if !info.exported {
paramInfos = append(paramInfos, paramInfo{llvmType: c.dataPtrType, name: "context", elemSize: 0})
}
var paramTypes []llvm.Type
for _, info := range paramInfos {
paramTypes = append(paramTypes, info.llvmType)
}
fnType := llvm.FunctionType(retType, paramTypes, info.variadic)
llvmFn = llvm.AddFunction(c.mod, info.linkName, fnType)
if strings.HasPrefix(c.Triple, "wasm") {
// C functions without prototypes like this:
// void foo();
// are actually variadic functions. However, it appears that it has been
// decided in WebAssembly that such prototype-less functions are not
// allowed in WebAssembly.
// In C, this can only happen when there are zero parameters, hence this
// check here. For more information:
// https://reviews.llvm.org/D48443
// https://github.com/WebAssembly/tool-conventions/issues/16
if info.variadic && len(fn.Params) == 0 {
attr := c.ctx.CreateStringAttribute("no-prototype", "")
llvmFn.AddFunctionAttr(attr)
}
}
c.addStandardDeclaredAttributes(llvmFn)
dereferenceableOrNullKind := llvm.AttributeKindID("dereferenceable_or_null")
for i, paramInfo := range paramInfos {
if paramInfo.elemSize != 0 {
dereferenceableOrNull := c.ctx.CreateEnumAttribute(dereferenceableOrNullKind, paramInfo.elemSize)
llvmFn.AddAttributeAtIndex(i+1, dereferenceableOrNull)
}
if info.noescape && paramInfo.flags¶mIsGoParam != 0 && paramInfo.llvmType.TypeKind() == llvm.PointerTypeKind {
// Parameters to functions with a //go:noescape parameter should get
// the nocapture attribute. However, the context parameter should
// not.
// (It may be safe to add the nocapture parameter to the context
// parameter, but I'd like to stay on the safe side here).
nocapture := c.ctx.CreateEnumAttribute(llvm.AttributeKindID("nocapture"), 0)
llvmFn.AddAttributeAtIndex(i+1, nocapture)
}
}
// Set a number of function or parameter attributes, depending on the
// function. These functions are runtime functions that are known to have
// certain attributes that might not be inferred by the compiler.
switch info.linkName {
case "abort":
// On *nix systems, the "abort" functuion in libc is used to handle fatal panics.
// Mark it as noreturn so LLVM can optimize away code.
llvmFn.AddFunctionAttr(c.ctx.CreateEnumAttribute(llvm.AttributeKindID("noreturn"), 0))
case "internal/abi.NoEscape":
llvmFn.AddAttributeAtIndex(1, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("nocapture"), 0))
case "runtime.alloc":
// Tell the optimizer that runtime.alloc is an allocator, meaning that it
// returns values that are never null and never alias to an existing value.
for _, attrName := range []string{"noalias", "nonnull"} {
llvmFn.AddAttributeAtIndex(0, c.ctx.CreateEnumAttribute(llvm.AttributeKindID(attrName), 0))
}
// Add attributes to signal to LLVM that this is an allocator function.
// This enables a number of optimizations.
llvmFn.AddFunctionAttr(c.ctx.CreateEnumAttribute(llvm.AttributeKindID("allockind"), allocKindAlloc|allocKindZeroed))
llvmFn.AddFunctionAttr(c.ctx.CreateStringAttribute("alloc-family", "runtime.alloc"))
// Use a special value to indicate the first parameter:
// > allocsize has two integer arguments, but because they're both 32 bits, we can
// > pack them into one 64-bit value, at the cost of making said value
// > nonsensical.
// >
// > In order to do this, we need to reserve one value of the second (optional)
// > allocsize argument to signify "not present."
llvmFn.AddFunctionAttr(c.ctx.CreateEnumAttribute(llvm.AttributeKindID("allocsize"), 0x0000_0000_ffff_ffff))
case "runtime.sliceAppend":
// Appending a slice will only read the to-be-appended slice, it won't
// be modified.
llvmFn.AddAttributeAtIndex(2, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("nocapture"), 0))
llvmFn.AddAttributeAtIndex(2, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("readonly"), 0))
case "runtime.sliceCopy":
// Copying a slice won't capture any of the parameters.
llvmFn.AddAttributeAtIndex(1, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("writeonly"), 0))
llvmFn.AddAttributeAtIndex(1, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("nocapture"), 0))
llvmFn.AddAttributeAtIndex(2, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("readonly"), 0))
llvmFn.AddAttributeAtIndex(2, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("nocapture"), 0))
case "runtime.stringFromBytes":
llvmFn.AddAttributeAtIndex(1, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("nocapture"), 0))
llvmFn.AddAttributeAtIndex(1, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("readonly"), 0))
case "runtime.stringFromRunes":
llvmFn.AddAttributeAtIndex(1, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("nocapture"), 0))
llvmFn.AddAttributeAtIndex(1, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("readonly"), 0))
case "runtime.trackPointer":
// This function is necessary for tracking pointers on the stack in a
// portable way (see gc_stack_portable.go). Indicate to the optimizer
// that the only thing we'll do is read the pointer.
llvmFn.AddAttributeAtIndex(1, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("nocapture"), 0))
llvmFn.AddAttributeAtIndex(1, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("readonly"), 0))
case "__mulsi3", "__divmodsi4", "__udivmodsi4":
if strings.Split(c.Triple, "-")[0] == "avr" {
// These functions are compiler-rt/libgcc functions that are
// currently implemented in Go. Assembly versions should appear in
// LLVM 17 hopefully. Until then, they need to be made available to
// the linker and the best way to do that is llvm.compiler.used.
// I considered adding a pragma for this, but the LLVM language
// reference explicitly says that this feature should not be exposed
// to source languages:
// > This is a rare construct that should only be used in rare
// > circumstances, and should not be exposed to source languages.
llvmutil.AppendToGlobal(c.mod, "llvm.compiler.used", llvmFn)
}
}
// External/exported functions may not retain pointer values.
// https://golang.org/cmd/cgo/#hdr-Passing_pointers
if info.exported {
if c.archFamily() == "wasm32" && len(fn.Blocks) == 0 {
// We need to add the wasm-import-module and the wasm-import-name
// attributes.
if info.wasmModule != "" {
llvmFn.AddFunctionAttr(c.ctx.CreateStringAttribute("wasm-import-module", info.wasmModule))
}
llvmFn.AddFunctionAttr(c.ctx.CreateStringAttribute("wasm-import-name", info.wasmName))
}
nocaptureKind := llvm.AttributeKindID("nocapture")
nocapture := c.ctx.CreateEnumAttribute(nocaptureKind, 0)
for i, typ := range paramTypes {
if typ.TypeKind() == llvm.PointerTypeKind {
llvmFn.AddAttributeAtIndex(i+1, nocapture)
}
}
}
// Build the function if needed.
c.maybeCreateSyntheticFunction(fn, llvmFn)
return fnType, llvmFn
}
// If this is a synthetic function (such as a generic function or a wrapper),
// create it now.
func (c *compilerContext) maybeCreateSyntheticFunction(fn *ssa.Function, llvmFn llvm.Value) {
// Synthetic functions are functions that do not appear in the source code,
// they are artificially constructed. Usually they are wrapper functions
// that are not referenced anywhere except in a SSA call instruction so
// should be created right away.
// The exception is the package initializer, which does appear in the
// *ssa.Package members and so shouldn't be created here.
if fn.Synthetic != "" && fn.Synthetic != "package initializer" && fn.Synthetic != "generic function" && fn.Synthetic != "range-over-func yield" {
if len(fn.Blocks) == 0 {
c.addError(fn.Pos(), "missing function body")
return
}
irbuilder := c.ctx.NewBuilder()
b := newBuilder(c, irbuilder, fn)
b.createFunction()
irbuilder.Dispose()
llvmFn.SetLinkage(llvm.LinkOnceODRLinkage)
llvmFn.SetUnnamedAddr(true)
}
}
// getFunctionInfo returns information about a function that is not directly
// present in *ssa.Function, such as the link name and whether it should be
// exported.
func (c *compilerContext) getFunctionInfo(f *ssa.Function) functionInfo {
if info, ok := c.functionInfos[f]; ok {
return info
}
info := functionInfo{
// Pick the default linkName.
linkName: f.RelString(nil),
}
// Check for a few runtime functions that are treated specially.
if info.linkName == "runtime.wasmEntryReactor" && c.BuildMode == "c-shared" {
info.linkName = "_initialize"
info.wasmName = "_initialize"
info.exported = true
}
if info.linkName == "runtime.wasmEntryCommand" && c.BuildMode == "default" {
info.linkName = "_start"
info.wasmName = "_start"
info.exported = true
}
// Check for //go: pragmas, which may change the link name (among others).
c.parsePragmas(&info, f)
c.functionInfos[f] = info
return info
}
// parsePragmas is used by getFunctionInfo to parse function pragmas such as
// //export or //go:noinline.
func (c *compilerContext) parsePragmas(info *functionInfo, f *ssa.Function) {
syntax := f.Syntax()
if f.Origin() != nil {
syntax = f.Origin().Syntax()
}
if syntax == nil {
return
}
// Read all pragmas of this function.
var pragmas []*ast.Comment
hasWasmExport := false
if decl, ok := syntax.(*ast.FuncDecl); ok && decl.Doc != nil {
for _, comment := range decl.Doc.List {
text := comment.Text
if strings.HasPrefix(text, "//go:") || strings.HasPrefix(text, "//export ") {
pragmas = append(pragmas, comment)
if strings.HasPrefix(comment.Text, "//go:wasmexport ") {
hasWasmExport = true
}
}
}
}
// Parse each pragma.
for _, comment := range pragmas {
parts := strings.Fields(comment.Text)
switch parts[0] {
case "//export", "//go:export":
if len(parts) != 2 {
continue
}
if hasWasmExport {
// //go:wasmexport overrides //export.
continue
}
info.linkName = parts[1]
info.wasmName = info.linkName
info.exported = true
case "//go:interrupt":
if hasUnsafeImport(f.Pkg.Pkg) {
info.interrupt = true
}
case "//go:wasm-module":
// Alternative comment for setting the import module.
// This is deprecated, use //go:wasmimport instead.
if len(parts) != 2 {
continue
}
info.wasmModule = parts[1]
case "//go:wasmimport":
// Import a WebAssembly function, for example a WASI function.
// Original proposal: https://github.com/golang/go/issues/38248
// Allow globally: https://github.com/golang/go/issues/59149
if len(parts) != 3 {
continue
}
if f.Blocks != nil {
// Defined functions cannot be exported.
c.addError(f.Pos(), "can only use //go:wasmimport on declarations")
continue
}
c.checkWasmImportExport(f, comment.Text)
info.exported = true
info.wasmModule = parts[1]
info.wasmName = parts[2]
case "//go:wasmexport":
if f.Blocks == nil {
c.addError(f.Pos(), "can only use //go:wasmexport on definitions")
continue
}
if len(parts) != 2 {
c.addError(f.Pos(), fmt.Sprintf("expected one parameter to //go:wasmexport, not %d", len(parts)-1))
continue
}
name := parts[1]
if name == "_start" || name == "_initialize" {
c.addError(f.Pos(), fmt.Sprintf("//go:wasmexport does not allow %#v", name))
continue
}
if c.BuildMode != "c-shared" && f.RelString(nil) == "main.main" {
c.addError(f.Pos(), fmt.Sprintf("//go:wasmexport does not allow main.main to be exported with -buildmode=%s", c.BuildMode))
continue
}
if c.archFamily() != "wasm32" {
c.addError(f.Pos(), "//go:wasmexport is only supported on wasm")
}
c.checkWasmImportExport(f, comment.Text)
info.wasmExport = name
info.wasmExportPos = comment.Slash
case "//go:inline":
info.inline = inlineHint
case "//go:noinline":
info.inline = inlineNone
case "//go:linkname":
if len(parts) != 3 || parts[1] != f.Name() {
continue
}
// Only enable go:linkname when the package imports "unsafe".
// This is a slightly looser requirement than what gc uses: gc
// requires the file to import "unsafe", not the package as a
// whole.
if hasUnsafeImport(f.Pkg.Pkg) {
info.linkName = parts[2]
}
case "//go:section":
// Only enable go:section when the package imports "unsafe".
// go:section also implies go:noinline since inlining could
// move the code to a different section than that requested.
if len(parts) == 2 && hasUnsafeImport(f.Pkg.Pkg) {
info.section = parts[1]
info.inline = inlineNone
}
case "//go:nobounds":
// Skip bounds checking in this function. Useful for some
// runtime functions.
// This is somewhat dangerous and thus only imported in packages
// that import unsafe.
if hasUnsafeImport(f.Pkg.Pkg) {
info.nobounds = true
}
case "//go:noescape":
// Don't let pointer parameters escape.
// Following the upstream Go implementation, we only do this for
// declarations, not definitions.
if len(f.Blocks) == 0 {
info.noescape = true
}
case "//go:variadic":
// The //go:variadic pragma is emitted by the CGo preprocessing
// pass for C variadic functions. This includes both explicit
// (with ...) and implicit (no parameters in signature)
// functions.
if strings.HasPrefix(f.Name(), "C.") {
// This prefix cannot naturally be created, it must have
// been created as a result of CGo preprocessing.
info.variadic = true
}
}
}
}
// Check whether this function can be used in //go:wasmimport or
// //go:wasmexport. It will add an error if this is not the case.
//
// The list of allowed types is based on this proposal:
// https://github.com/golang/go/issues/59149
func (c *compilerContext) checkWasmImportExport(f *ssa.Function, pragma string) {
if c.pkg.Path() == "runtime" || c.pkg.Path() == "syscall/js" || c.pkg.Path() == "syscall" {
// The runtime is a special case. Allow all kinds of parameters
// (importantly, including pointers).
return
}
if f.Signature.Results().Len() > 1 {
c.addError(f.Signature.Results().At(1).Pos(), fmt.Sprintf("%s: too many return values", pragma))
} else if f.Signature.Results().Len() == 1 {
result := f.Signature.Results().At(0)
if !c.isValidWasmType(result.Type(), siteResult) {
c.addError(result.Pos(), fmt.Sprintf("%s: unsupported result type %s", pragma, result.Type().String()))
}
}
for _, param := range f.Params {
// Check whether the type is allowed.
// Only a very limited number of types can be mapped to WebAssembly.
if !c.isValidWasmType(param.Type(), siteParam) {
c.addError(param.Pos(), fmt.Sprintf("%s: unsupported parameter type %s", pragma, param.Type().String()))
}
}
}
// Check whether the type maps directly to a WebAssembly type.
//
// This reflects the relaxed type restrictions proposed here (except for structs.HostLayout):
// https://github.com/golang/go/issues/66984
//
// This previously reflected the additional restrictions documented here:
// https://github.com/golang/go/issues/59149
func (c *compilerContext) isValidWasmType(typ types.Type, site wasmSite) bool {
switch typ := typ.Underlying().(type) {
case *types.Basic:
switch typ.Kind() {
case types.Bool:
return true
case types.Int8, types.Uint8, types.Int16, types.Uint16:
return site == siteIndirect
case types.Int32, types.Uint32, types.Int64, types.Uint64:
return true
case types.Float32, types.Float64:
return true
case types.Uintptr, types.UnsafePointer:
return true
case types.String:
// string flattens to two values, so disallowed as a result
return site == siteParam || site == siteIndirect
}
case *types.Array:
return site == siteIndirect && c.isValidWasmType(typ.Elem(), siteIndirect)
case *types.Struct:
if site != siteIndirect {
return false
}
// Structs with no fields do not need structs.HostLayout
if typ.NumFields() == 0 {
return true
}
hasHostLayout := true // default to true before detecting Go version
// (*types.Package).GoVersion added in go1.21
if gv, ok := any(c.pkg).(interface{ GoVersion() string }); ok {
if goenv.Compare(gv.GoVersion(), "go1.23") >= 0 {
hasHostLayout = false // package structs added in go1.23
}
}
for i := 0; i < typ.NumFields(); i++ {
ftyp := typ.Field(i).Type()
if ftyp.String() == "structs.HostLayout" {
hasHostLayout = true
continue
}
if !c.isValidWasmType(ftyp, siteIndirect) {
return false
}
}
return hasHostLayout
case *types.Pointer:
return c.isValidWasmType(typ.Elem(), siteIndirect)
}
return false
}
type wasmSite int
const (
siteParam wasmSite = iota
siteResult
siteIndirect // pointer or field
)
// getParams returns the function parameters, including the receiver at the
// start. This is an alternative to the Params member of *ssa.Function, which is
// not yet populated when the package has not yet been built.
func getParams(sig *types.Signature) []*types.Var {
params := []*types.Var{}
if sig.Recv() != nil {
params = append(params, sig.Recv())
}
for i := 0; i < sig.Params().Len(); i++ {
params = append(params, sig.Params().At(i))
}
return params
}
// addStandardDeclaredAttributes adds attributes that are set for any function,
// whether declared or defined.
func (c *compilerContext) addStandardDeclaredAttributes(llvmFn llvm.Value) {
if c.SizeLevel >= 1 {
// Set the "optsize" attribute to make slightly smaller binaries at the
// cost of minimal performance loss (-Os in Clang).
kind := llvm.AttributeKindID("optsize")
attr := c.ctx.CreateEnumAttribute(kind, 0)
llvmFn.AddFunctionAttr(attr)
}
if c.SizeLevel >= 2 {
// Set the "minsize" attribute to reduce code size even further,
// regardless of performance loss (-Oz in Clang).
kind := llvm.AttributeKindID("minsize")
attr := c.ctx.CreateEnumAttribute(kind, 0)
llvmFn.AddFunctionAttr(attr)
}
if c.CPU != "" {
llvmFn.AddFunctionAttr(c.ctx.CreateStringAttribute("target-cpu", c.CPU))
}
if c.Features != "" {
llvmFn.AddFunctionAttr(c.ctx.CreateStringAttribute("target-features", c.Features))
}
}
// addStandardDefinedAttributes adds the set of attributes that are added to
// every function defined by TinyGo (even thunks/wrappers), possibly depending
// on the architecture. It does not set attributes only set for declared
// functions, use addStandardDeclaredAttributes for this.
func (c *compilerContext) addStandardDefinedAttributes(llvmFn llvm.Value) {
// TinyGo does not currently raise exceptions, so set the 'nounwind' flag.
// This behavior matches Clang when compiling C source files.
// It reduces binary size on Linux a little bit on non-x86_64 targets by
// eliminating exception tables for these functions.
llvmFn.AddFunctionAttr(c.ctx.CreateEnumAttribute(llvm.AttributeKindID("nounwind"), 0))
if strings.Split(c.Triple, "-")[0] == "x86_64" {
// Required by the ABI.
// The uwtable has two possible values: sync (1) or async (2). We use
// sync because we currently don't use async unwind tables.
// For details, see: https://llvm.org/docs/LangRef.html#function-attributes
llvmFn.AddFunctionAttr(c.ctx.CreateEnumAttribute(llvm.AttributeKindID("uwtable"), 1))
}
}
// addStandardAttributes adds all attributes added to defined functions.
func (c *compilerContext) addStandardAttributes(llvmFn llvm.Value) {
c.addStandardDeclaredAttributes(llvmFn)
c.addStandardDefinedAttributes(llvmFn)
}
// globalInfo contains some information about a specific global. By default,
// linkName is equal to .RelString(nil) on a global and extern is false, but for
// some symbols this is different (due to //go:extern for example).
type globalInfo struct {
linkName string // go:extern
extern bool // go:extern
align int // go:align
section string // go:section
}
// loadASTComments loads comments on globals from the AST, for use later in the
// program. In particular, they are required for //go:extern pragmas on globals.
func (c *compilerContext) loadASTComments(pkg *loader.Package) {
for _, file := range pkg.Files {
for _, decl := range file.Decls {
switch decl := decl.(type) {
case *ast.GenDecl:
switch decl.Tok {
case token.VAR:
if len(decl.Specs) != 1 {
continue
}
for _, spec := range decl.Specs {
switch spec := spec.(type) {
case *ast.ValueSpec: // decl.Tok == token.VAR
for _, name := range spec.Names {
id := pkg.Pkg.Path() + "." + name.Name
c.astComments[id] = decl.Doc
}
}
}
}
}
}
}
}
// getGlobal returns a LLVM IR global value for a Go SSA global. It is added to
// the LLVM IR if it has not been added already.
func (c *compilerContext) getGlobal(g *ssa.Global) llvm.Value {
info := c.getGlobalInfo(g)
llvmGlobal := c.mod.NamedGlobal(info.linkName)
if llvmGlobal.IsNil() {
typ := g.Type().(*types.Pointer).Elem()
llvmType := c.getLLVMType(typ)
llvmGlobal = llvm.AddGlobal(c.mod, llvmType, info.linkName)
// Set alignment from the //go:align comment.
alignment := c.targetData.ABITypeAlignment(llvmType)
if info.align > alignment {
alignment = info.align
}
if alignment <= 0 || alignment&(alignment-1) != 0 {
// Check for power-of-two (or 0).
// See: https://stackoverflow.com/a/108360
c.addError(g.Pos(), "global variable alignment must be a positive power of two")
} else {
// Set the alignment only when it is a power of two.
llvmGlobal.SetAlignment(alignment)
}
if c.Debug && !info.extern {
// Add debug info.
pos := c.program.Fset.Position(g.Pos())
diglobal := c.dibuilder.CreateGlobalVariableExpression(c.difiles[pos.Filename], llvm.DIGlobalVariableExpression{
Name: g.RelString(nil),
LinkageName: info.linkName,
File: c.getDIFile(pos.Filename),
Line: pos.Line,
Type: c.getDIType(typ),
LocalToUnit: false,
Expr: c.dibuilder.CreateExpression(nil),
AlignInBits: uint32(alignment) * 8,
})
llvmGlobal.AddMetadata(0, diglobal)
}
}
return llvmGlobal
}
// getGlobalInfo returns some information about a specific global.
func (c *compilerContext) getGlobalInfo(g *ssa.Global) globalInfo {
info := globalInfo{
// Pick the default linkName.
linkName: g.RelString(nil),
}
// Check for //go: pragmas, which may change the link name (among others).
doc := c.astComments[info.linkName]
if doc != nil {
info.parsePragmas(doc)
}
return info
}
// Parse //go: pragma comments from the source. In particular, it parses the
// //go:extern pragma on globals.
func (info *globalInfo) parsePragmas(doc *ast.CommentGroup) {
for _, comment := range doc.List {
if !strings.HasPrefix(comment.Text, "//go:") {
continue
}
parts := strings.Fields(comment.Text)
switch parts[0] {
case "//go:extern":
info.extern = true
if len(parts) == 2 {
info.linkName = parts[1]
}
case "//go:align":
align, err := strconv.Atoi(parts[1])
if err == nil {
info.align = align
}
case "//go:section":
if len(parts) == 2 {
info.section = parts[1]
}
}
}
}
// Get all methods of a type.
func getAllMethods(prog *ssa.Program, typ types.Type) []*types.Selection {
ms := prog.MethodSets.MethodSet(typ)
methods := make([]*types.Selection, ms.Len())
for i := 0; i < ms.Len(); i++ {
methods[i] = ms.At(i)
}
return methods
}
// Return true if this package imports "unsafe", false otherwise.
func hasUnsafeImport(pkg *types.Package) bool {
for _, imp := range pkg.Imports() {
if imp == types.Unsafe {
return true
}
}
return false
}
|