summaryrefslogtreecommitdiffstats
path: root/src/cmd/compile/internal/walk/walk.go
blob: 001edcc3325c223c6cb72785c03b913a1c0e0f4e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
// Copyright 2009 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 walk

import (
	"fmt"

	"cmd/compile/internal/base"
	"cmd/compile/internal/ir"
	"cmd/compile/internal/reflectdata"
	"cmd/compile/internal/ssagen"
	"cmd/compile/internal/typecheck"
	"cmd/compile/internal/types"
	"cmd/internal/src"
)

// The constant is known to runtime.
const tmpstringbufsize = 32

func Walk(fn *ir.Func) {
	ir.CurFunc = fn
	errorsBefore := base.Errors()
	order(fn)
	if base.Errors() > errorsBefore {
		return
	}

	if base.Flag.W != 0 {
		s := fmt.Sprintf("\nbefore walk %v", ir.CurFunc.Sym())
		ir.DumpList(s, ir.CurFunc.Body)
	}

	lno := base.Pos

	base.Pos = lno
	if base.Errors() > errorsBefore {
		return
	}
	walkStmtList(ir.CurFunc.Body)
	if base.Flag.W != 0 {
		s := fmt.Sprintf("after walk %v", ir.CurFunc.Sym())
		ir.DumpList(s, ir.CurFunc.Body)
	}

	// Eagerly compute sizes of all variables for SSA.
	for _, n := range fn.Dcl {
		types.CalcSize(n.Type())
	}
}

// walkRecv walks an ORECV node.
func walkRecv(n *ir.UnaryExpr) ir.Node {
	if n.Typecheck() == 0 {
		base.Fatalf("missing typecheck: %+v", n)
	}
	init := ir.TakeInit(n)

	n.X = walkExpr(n.X, &init)
	call := walkExpr(mkcall1(chanfn("chanrecv1", 2, n.X.Type()), nil, &init, n.X, typecheck.NodNil()), &init)
	return ir.InitExpr(init, call)
}

func convas(n *ir.AssignStmt, init *ir.Nodes) *ir.AssignStmt {
	if n.Op() != ir.OAS {
		base.Fatalf("convas: not OAS %v", n.Op())
	}
	n.SetTypecheck(1)

	if n.X == nil || n.Y == nil {
		return n
	}

	lt := n.X.Type()
	rt := n.Y.Type()
	if lt == nil || rt == nil {
		return n
	}

	if ir.IsBlank(n.X) {
		n.Y = typecheck.DefaultLit(n.Y, nil)
		return n
	}

	if !types.Identical(lt, rt) {
		n.Y = typecheck.AssignConv(n.Y, lt, "assignment")
		n.Y = walkExpr(n.Y, init)
	}
	types.CalcSize(n.Y.Type())

	return n
}

func vmkcall(fn ir.Node, t *types.Type, init *ir.Nodes, va []ir.Node) *ir.CallExpr {
	if init == nil {
		base.Fatalf("mkcall with nil init: %v", fn)
	}
	if fn.Type() == nil || fn.Type().Kind() != types.TFUNC {
		base.Fatalf("mkcall %v %v", fn, fn.Type())
	}

	n := fn.Type().NumParams()
	if n != len(va) {
		base.Fatalf("vmkcall %v needs %v args got %v", fn, n, len(va))
	}

	call := typecheck.Call(base.Pos, fn, va, false).(*ir.CallExpr)
	call.SetType(t)
	return walkExpr(call, init).(*ir.CallExpr)
}

func mkcall(name string, t *types.Type, init *ir.Nodes, args ...ir.Node) *ir.CallExpr {
	return vmkcall(typecheck.LookupRuntime(name), t, init, args)
}

func mkcallstmt(name string, args ...ir.Node) ir.Node {
	return mkcallstmt1(typecheck.LookupRuntime(name), args...)
}

func mkcall1(fn ir.Node, t *types.Type, init *ir.Nodes, args ...ir.Node) *ir.CallExpr {
	return vmkcall(fn, t, init, args)
}

func mkcallstmt1(fn ir.Node, args ...ir.Node) ir.Node {
	var init ir.Nodes
	n := vmkcall(fn, nil, &init, args)
	if len(init) == 0 {
		return n
	}
	init.Append(n)
	return ir.NewBlockStmt(n.Pos(), init)
}

func chanfn(name string, n int, t *types.Type) ir.Node {
	if !t.IsChan() {
		base.Fatalf("chanfn %v", t)
	}
	switch n {
	case 1:
		return typecheck.LookupRuntime(name, t.Elem())
	case 2:
		return typecheck.LookupRuntime(name, t.Elem(), t.Elem())
	}
	base.Fatalf("chanfn %d", n)
	return nil
}

func mapfn(name string, t *types.Type, isfat bool) ir.Node {
	if !t.IsMap() {
		base.Fatalf("mapfn %v", t)
	}
	if mapfast(t) == mapslow || isfat {
		return typecheck.LookupRuntime(name, t.Key(), t.Elem(), t.Key(), t.Elem())
	}
	return typecheck.LookupRuntime(name, t.Key(), t.Elem(), t.Elem())
}

func mapfndel(name string, t *types.Type) ir.Node {
	if !t.IsMap() {
		base.Fatalf("mapfn %v", t)
	}
	if mapfast(t) == mapslow {
		return typecheck.LookupRuntime(name, t.Key(), t.Elem(), t.Key())
	}
	return typecheck.LookupRuntime(name, t.Key(), t.Elem())
}

const (
	mapslow = iota
	mapfast32
	mapfast32ptr
	mapfast64
	mapfast64ptr
	mapfaststr
	nmapfast
)

type mapnames [nmapfast]string

func mkmapnames(base string, ptr string) mapnames {
	return mapnames{base, base + "_fast32", base + "_fast32" + ptr, base + "_fast64", base + "_fast64" + ptr, base + "_faststr"}
}

var mapaccess1 = mkmapnames("mapaccess1", "")
var mapaccess2 = mkmapnames("mapaccess2", "")
var mapassign = mkmapnames("mapassign", "ptr")
var mapdelete = mkmapnames("mapdelete", "")

func mapfast(t *types.Type) int {
	// Check runtime/map.go:maxElemSize before changing.
	if t.Elem().Size() > 128 {
		return mapslow
	}
	switch reflectdata.AlgType(t.Key()) {
	case types.AMEM32:
		if !t.Key().HasPointers() {
			return mapfast32
		}
		if types.PtrSize == 4 {
			return mapfast32ptr
		}
		base.Fatalf("small pointer %v", t.Key())
	case types.AMEM64:
		if !t.Key().HasPointers() {
			return mapfast64
		}
		if types.PtrSize == 8 {
			return mapfast64ptr
		}
		// Two-word object, at least one of which is a pointer.
		// Use the slow path.
	case types.ASTRING:
		return mapfaststr
	}
	return mapslow
}

func walkAppendArgs(n *ir.CallExpr, init *ir.Nodes) {
	walkExprListSafe(n.Args, init)

	// walkExprListSafe will leave OINDEX (s[n]) alone if both s
	// and n are name or literal, but those may index the slice we're
	// modifying here. Fix explicitly.
	ls := n.Args
	for i1, n1 := range ls {
		ls[i1] = cheapExpr(n1, init)
	}
}

// appendWalkStmt typechecks and walks stmt and then appends it to init.
func appendWalkStmt(init *ir.Nodes, stmt ir.Node) {
	op := stmt.Op()
	n := typecheck.Stmt(stmt)
	if op == ir.OAS || op == ir.OAS2 {
		// If the assignment has side effects, walkExpr will append them
		// directly to init for us, while walkStmt will wrap it in an OBLOCK.
		// We need to append them directly.
		// TODO(rsc): Clean this up.
		n = walkExpr(n, init)
	} else {
		n = walkStmt(n)
	}
	init.Append(n)
}

// The max number of defers in a function using open-coded defers. We enforce this
// limit because the deferBits bitmask is currently a single byte (to minimize code size)
const maxOpenDefers = 8

// backingArrayPtrLen extracts the pointer and length from a slice or string.
// This constructs two nodes referring to n, so n must be a cheapExpr.
func backingArrayPtrLen(n ir.Node) (ptr, length ir.Node) {
	var init ir.Nodes
	c := cheapExpr(n, &init)
	if c != n || len(init) != 0 {
		base.Fatalf("backingArrayPtrLen not cheap: %v", n)
	}
	ptr = ir.NewUnaryExpr(base.Pos, ir.OSPTR, n)
	if n.Type().IsString() {
		ptr.SetType(types.Types[types.TUINT8].PtrTo())
	} else {
		ptr.SetType(n.Type().Elem().PtrTo())
	}
	ptr.SetTypecheck(1)
	length = ir.NewUnaryExpr(base.Pos, ir.OLEN, n)
	length.SetType(types.Types[types.TINT])
	length.SetTypecheck(1)
	return ptr, length
}

// mayCall reports whether evaluating expression n may require
// function calls, which could clobber function call arguments/results
// currently on the stack.
func mayCall(n ir.Node) bool {
	// When instrumenting, any expression might require function calls.
	if base.Flag.Cfg.Instrumenting {
		return true
	}

	isSoftFloat := func(typ *types.Type) bool {
		return types.IsFloat[typ.Kind()] || types.IsComplex[typ.Kind()]
	}

	return ir.Any(n, func(n ir.Node) bool {
		// walk should have already moved any Init blocks off of
		// expressions.
		if len(n.Init()) != 0 {
			base.FatalfAt(n.Pos(), "mayCall %+v", n)
		}

		switch n.Op() {
		default:
			base.FatalfAt(n.Pos(), "mayCall %+v", n)

		case ir.OCALLFUNC, ir.OCALLINTER,
			ir.OUNSAFEADD, ir.OUNSAFESLICE:
			return true

		case ir.OINDEX, ir.OSLICE, ir.OSLICEARR, ir.OSLICE3, ir.OSLICE3ARR, ir.OSLICESTR,
			ir.ODEREF, ir.ODOTPTR, ir.ODOTTYPE, ir.ODYNAMICDOTTYPE, ir.ODIV, ir.OMOD,
			ir.OSLICE2ARR, ir.OSLICE2ARRPTR:
			// These ops might panic, make sure they are done
			// before we start marshaling args for a call. See issue 16760.
			return true

		case ir.OANDAND, ir.OOROR:
			n := n.(*ir.LogicalExpr)
			// The RHS expression may have init statements that
			// should only execute conditionally, and so cannot be
			// pulled out to the top-level init list. We could try
			// to be more precise here.
			return len(n.Y.Init()) != 0

		// When using soft-float, these ops might be rewritten to function calls
		// so we ensure they are evaluated first.
		case ir.OADD, ir.OSUB, ir.OMUL, ir.ONEG:
			return ssagen.Arch.SoftFloat && isSoftFloat(n.Type())
		case ir.OLT, ir.OEQ, ir.ONE, ir.OLE, ir.OGE, ir.OGT:
			n := n.(*ir.BinaryExpr)
			return ssagen.Arch.SoftFloat && isSoftFloat(n.X.Type())
		case ir.OCONV:
			n := n.(*ir.ConvExpr)
			return ssagen.Arch.SoftFloat && (isSoftFloat(n.Type()) || isSoftFloat(n.X.Type()))

		case ir.OMIN, ir.OMAX:
			// string or float requires runtime call, see (*ssagen.state).minmax method.
			return n.Type().IsString() || n.Type().IsFloat()

		case ir.OLITERAL, ir.ONIL, ir.ONAME, ir.OLINKSYMOFFSET, ir.OMETHEXPR,
			ir.OAND, ir.OANDNOT, ir.OLSH, ir.OOR, ir.ORSH, ir.OXOR, ir.OCOMPLEX, ir.OMAKEFACE,
			ir.OADDR, ir.OBITNOT, ir.ONOT, ir.OPLUS,
			ir.OCAP, ir.OIMAG, ir.OLEN, ir.OREAL,
			ir.OCONVNOP, ir.ODOT,
			ir.OCFUNC, ir.OIDATA, ir.OITAB, ir.OSPTR,
			ir.OBYTES2STRTMP, ir.OGETG, ir.OGETCALLERPC, ir.OGETCALLERSP, ir.OSLICEHEADER, ir.OSTRINGHEADER:
			// ok: operations that don't require function calls.
			// Expand as needed.
		}

		return false
	})
}

// itabType loads the _type field from a runtime.itab struct.
func itabType(itab ir.Node) ir.Node {
	if itabTypeField == nil {
		// runtime.itab's _type field
		itabTypeField = runtimeField("_type", int64(types.PtrSize), types.NewPtr(types.Types[types.TUINT8]))
	}
	return boundedDotPtr(base.Pos, itab, itabTypeField)
}

var itabTypeField *types.Field

// boundedDotPtr returns a selector expression representing ptr.field
// and omits nil-pointer checks for ptr.
func boundedDotPtr(pos src.XPos, ptr ir.Node, field *types.Field) *ir.SelectorExpr {
	sel := ir.NewSelectorExpr(pos, ir.ODOTPTR, ptr, field.Sym)
	sel.Selection = field
	sel.SetType(field.Type)
	sel.SetTypecheck(1)
	sel.SetBounded(true) // guaranteed not to fault
	return sel
}

func runtimeField(name string, offset int64, typ *types.Type) *types.Field {
	f := types.NewField(src.NoXPos, ir.Pkgs.Runtime.Lookup(name), typ)
	f.Offset = offset
	return f
}

// ifaceData loads the data field from an interface.
// The concrete type must be known to have type t.
// It follows the pointer if !IsDirectIface(t).
func ifaceData(pos src.XPos, n ir.Node, t *types.Type) ir.Node {
	if t.IsInterface() {
		base.Fatalf("ifaceData interface: %v", t)
	}
	ptr := ir.NewUnaryExpr(pos, ir.OIDATA, n)
	if types.IsDirectIface(t) {
		ptr.SetType(t)
		ptr.SetTypecheck(1)
		return ptr
	}
	ptr.SetType(types.NewPtr(t))
	ptr.SetTypecheck(1)
	ind := ir.NewStarExpr(pos, ptr)
	ind.SetType(t)
	ind.SetTypecheck(1)
	ind.SetBounded(true)
	return ind
}