[dev.regabi] cmd/compile: move type size calculations into package types [generated]

To break up package gc, we need to put these calculations somewhere
lower in the import graph, either an existing or new package. Package types
already needs this code and is using hacks to get it without an import cycle.
We can remove the hacks and set up for the new package gc by moving the
code into package types itself.

[git-generate]
cd src/cmd/compile/internal/gc
rf '
	# Remove old import cycle hacks in gc.
	rm TypecheckInit:/types.Widthptr =/-0,/types.Dowidth =/+0 \
		../ssa/export_test.go:/types.Dowidth =/-+
	ex {
		import "cmd/compile/internal/types"
		types.Widthptr -> Widthptr
		types.Dowidth -> dowidth
	}

	# Disable CalcSize in tests instead of base.Fatalf
	sub dowidth:/base.Fatalf\("dowidth without betypeinit"\)/ \
		// Assume this is a test. \
		return

	# Move size calculation into cmd/compile/internal/types
	mv Widthptr PtrSize
	mv Widthreg RegSize
	mv slicePtrOffset SlicePtrOffset
	mv sliceLenOffset SliceLenOffset
	mv sliceCapOffset SliceCapOffset
	mv sizeofSlice SliceSize
	mv sizeofString StringSize
	mv skipDowidthForTracing SkipSizeForTracing
	mv dowidth CalcSize
	mv checkwidth CheckSize
	mv widstruct calcStructOffset
	mv sizeCalculationDisabled CalcSizeDisabled
	mv defercheckwidth DeferCheckSize
	mv resumecheckwidth ResumeCheckSize
	mv typeptrdata PtrDataSize
	mv \
		PtrSize RegSize SlicePtrOffset SkipSizeForTracing typePos align.go PtrDataSize \
		size.go
	mv size.go cmd/compile/internal/types
'

: # Remove old import cycle hacks in types.
cd ../types
rf '
	ex {
		Widthptr -> PtrSize
		Dowidth -> CalcSize
	}
	rm Widthptr Dowidth
'

Change-Id: Ib96cdc6bda2617235480c29392ea5cfb20f60cd8
Reviewed-on: https://go-review.googlesource.com/c/go/+/279234
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 634 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/types/size.go b/src/cmd/compile/internal/types/size.go
new file mode 100644
index 0000000000..a54c086ded
--- /dev/null
+++ b/src/cmd/compile/internal/types/size.go
@@ -0,0 +1,634 @@
+// 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 types
+
+import (
+	"bytes"
+	"fmt"
+	"sort"
+
+	"cmd/compile/internal/base"
+	"cmd/internal/src"
+)
+
+var PtrSize int
+
+var RegSize int
+
+// Slices in the runtime are represented by three components:
+//
+// type slice struct {
+// 	ptr unsafe.Pointer
+// 	len int
+// 	cap int
+// }
+//
+// Strings in the runtime are represented by two components:
+//
+// type string struct {
+// 	ptr unsafe.Pointer
+// 	len int
+// }
+//
+// These variables are the offsets of fields and sizes of these structs.
+var (
+	SlicePtrOffset int64
+	SliceLenOffset int64
+	SliceCapOffset int64
+
+	SliceSize  int64
+	StringSize int64
+)
+
+var SkipSizeForTracing bool
+
+// typePos returns the position associated with t.
+// This is where t was declared or where it appeared as a type expression.
+func typePos(t *Type) src.XPos {
+	if pos := t.Pos(); pos.IsKnown() {
+		return pos
+	}
+	base.Fatalf("bad type: %v", t)
+	panic("unreachable")
+}
+
+// MaxWidth is the maximum size of a value on the target architecture.
+var MaxWidth int64
+
+// CalcSizeDisabled indicates whether it is safe
+// to calculate Types' widths and alignments. See dowidth.
+var CalcSizeDisabled bool
+
+// machine size and rounding alignment is dictated around
+// the size of a pointer, set in betypeinit (see ../amd64/galign.go).
+var defercalc int
+
+func Rnd(o int64, r int64) int64 {
+	if r < 1 || r > 8 || r&(r-1) != 0 {
+		base.Fatalf("rnd %d", r)
+	}
+	return (o + r - 1) &^ (r - 1)
+}
+
+// expandiface computes the method set for interface type t by
+// expanding embedded interfaces.
+func expandiface(t *Type) {
+	seen := make(map[*Sym]*Field)
+	var methods []*Field
+
+	addMethod := func(m *Field, explicit bool) {
+		switch prev := seen[m.Sym]; {
+		case prev == nil:
+			seen[m.Sym] = m
+		case AllowsGoVersion(t.Pkg(), 1, 14) && !explicit && Identical(m.Type, prev.Type):
+			return
+		default:
+			base.ErrorfAt(m.Pos, "duplicate method %s", m.Sym.Name)
+		}
+		methods = append(methods, m)
+	}
+
+	for _, m := range t.Methods().Slice() {
+		if m.Sym == nil {
+			continue
+		}
+
+		CheckSize(m.Type)
+		addMethod(m, true)
+	}
+
+	for _, m := range t.Methods().Slice() {
+		if m.Sym != nil {
+			continue
+		}
+
+		if !m.Type.IsInterface() {
+			base.ErrorfAt(m.Pos, "interface contains embedded non-interface %v", m.Type)
+			m.SetBroke(true)
+			t.SetBroke(true)
+			// Add to fields so that error messages
+			// include the broken embedded type when
+			// printing t.
+			// TODO(mdempsky): Revisit this.
+			methods = append(methods, m)
+			continue
+		}
+
+		// Embedded interface: duplicate all methods
+		// (including broken ones, if any) and add to t's
+		// method set.
+		for _, t1 := range m.Type.Fields().Slice() {
+			// Use m.Pos rather than t1.Pos to preserve embedding position.
+			f := NewField(m.Pos, t1.Sym, t1.Type)
+			addMethod(f, false)
+		}
+	}
+
+	sort.Sort(MethodsByName(methods))
+
+	if int64(len(methods)) >= MaxWidth/int64(PtrSize) {
+		base.ErrorfAt(typePos(t), "interface too large")
+	}
+	for i, m := range methods {
+		m.Offset = int64(i) * int64(PtrSize)
+	}
+
+	// Access fields directly to avoid recursively calling dowidth
+	// within Type.Fields().
+	t.Extra.(*Interface).Fields.Set(methods)
+}
+
+func calcStructOffset(errtype *Type, t *Type, o int64, flag int) int64 {
+	starto := o
+	maxalign := int32(flag)
+	if maxalign < 1 {
+		maxalign = 1
+	}
+	lastzero := int64(0)
+	for _, f := range t.Fields().Slice() {
+		if f.Type == nil {
+			// broken field, just skip it so that other valid fields
+			// get a width.
+			continue
+		}
+
+		CalcSize(f.Type)
+		if int32(f.Type.Align) > maxalign {
+			maxalign = int32(f.Type.Align)
+		}
+		if f.Type.Align > 0 {
+			o = Rnd(o, int64(f.Type.Align))
+		}
+		f.Offset = o
+		if f.Nname != nil {
+			// addrescapes has similar code to update these offsets.
+			// Usually addrescapes runs after widstruct,
+			// in which case we could drop this,
+			// but function closure functions are the exception.
+			// NOTE(rsc): This comment may be stale.
+			// It's possible the ordering has changed and this is
+			// now the common case. I'm not sure.
+			f.Nname.(VarObject).RecordFrameOffset(o)
+		}
+
+		w := f.Type.Width
+		if w < 0 {
+			base.Fatalf("invalid width %d", f.Type.Width)
+		}
+		if w == 0 {
+			lastzero = o
+		}
+		o += w
+		maxwidth := MaxWidth
+		// On 32-bit systems, reflect tables impose an additional constraint
+		// that each field start offset must fit in 31 bits.
+		if maxwidth < 1<<32 {
+			maxwidth = 1<<31 - 1
+		}
+		if o >= maxwidth {
+			base.ErrorfAt(typePos(errtype), "type %L too large", errtype)
+			o = 8 // small but nonzero
+		}
+	}
+
+	// For nonzero-sized structs which end in a zero-sized thing, we add
+	// an extra byte of padding to the type. This padding ensures that
+	// taking the address of the zero-sized thing can't manufacture a
+	// pointer to the next object in the heap. See issue 9401.
+	if flag == 1 && o > starto && o == lastzero {
+		o++
+	}
+
+	// final width is rounded
+	if flag != 0 {
+		o = Rnd(o, int64(maxalign))
+	}
+	t.Align = uint8(maxalign)
+
+	// type width only includes back to first field's offset
+	t.Width = o - starto
+
+	return o
+}
+
+// findTypeLoop searches for an invalid type declaration loop involving
+// type t and reports whether one is found. If so, path contains the
+// loop.
+//
+// path points to a slice used for tracking the sequence of types
+// visited. Using a pointer to a slice allows the slice capacity to
+// grow and limit reallocations.
+func findTypeLoop(t *Type, path *[]*Type) bool {
+	// We implement a simple DFS loop-finding algorithm. This
+	// could be faster, but type cycles are rare.
+
+	if t.Sym() != nil {
+		// Declared type. Check for loops and otherwise
+		// recurse on the type expression used in the type
+		// declaration.
+
+		// Type imported from package, so it can't be part of
+		// a type loop (otherwise that package should have
+		// failed to compile).
+		if t.Sym().Pkg != LocalPkg {
+			return false
+		}
+
+		for i, x := range *path {
+			if x == t {
+				*path = (*path)[i:]
+				return true
+			}
+		}
+
+		*path = append(*path, t)
+		if findTypeLoop(t.Obj().(TypeObject).TypeDefn(), path) {
+			return true
+		}
+		*path = (*path)[:len(*path)-1]
+	} else {
+		// Anonymous type. Recurse on contained types.
+
+		switch t.Kind() {
+		case TARRAY:
+			if findTypeLoop(t.Elem(), path) {
+				return true
+			}
+		case TSTRUCT:
+			for _, f := range t.Fields().Slice() {
+				if findTypeLoop(f.Type, path) {
+					return true
+				}
+			}
+		case TINTER:
+			for _, m := range t.Methods().Slice() {
+				if m.Type.IsInterface() { // embedded interface
+					if findTypeLoop(m.Type, path) {
+						return true
+					}
+				}
+			}
+		}
+	}
+
+	return false
+}
+
+func reportTypeLoop(t *Type) {
+	if t.Broke() {
+		return
+	}
+
+	var l []*Type
+	if !findTypeLoop(t, &l) {
+		base.Fatalf("failed to find type loop for: %v", t)
+	}
+
+	// Rotate loop so that the earliest type declaration is first.
+	i := 0
+	for j, t := range l[1:] {
+		if typePos(t).Before(typePos(l[i])) {
+			i = j + 1
+		}
+	}
+	l = append(l[i:], l[:i]...)
+
+	var msg bytes.Buffer
+	fmt.Fprintf(&msg, "invalid recursive type %v\n", l[0])
+	for _, t := range l {
+		fmt.Fprintf(&msg, "\t%v: %v refers to\n", base.FmtPos(typePos(t)), t)
+		t.SetBroke(true)
+	}
+	fmt.Fprintf(&msg, "\t%v: %v", base.FmtPos(typePos(l[0])), l[0])
+	base.ErrorfAt(typePos(l[0]), msg.String())
+}
+
+// CalcSize calculates and stores the size and alignment for t.
+// If sizeCalculationDisabled is set, and the size/alignment
+// have not already been calculated, it calls Fatal.
+// This is used to prevent data races in the back end.
+func CalcSize(t *Type) {
+	// Calling dowidth when typecheck tracing enabled is not safe.
+	// See issue #33658.
+	if base.EnableTrace && SkipSizeForTracing {
+		return
+	}
+	if PtrSize == 0 {
+
+		// Assume this is a test.
+		return
+	}
+
+	if t == nil {
+		return
+	}
+
+	if t.Width == -2 {
+		reportTypeLoop(t)
+		t.Width = 0
+		t.Align = 1
+		return
+	}
+
+	if t.WidthCalculated() {
+		return
+	}
+
+	if CalcSizeDisabled {
+		if t.Broke() {
+			// break infinite recursion from Fatal call below
+			return
+		}
+		t.SetBroke(true)
+		base.Fatalf("width not calculated: %v", t)
+	}
+
+	// break infinite recursion if the broken recursive type
+	// is referenced again
+	if t.Broke() && t.Width == 0 {
+		return
+	}
+
+	// defer checkwidth calls until after we're done
+	DeferCheckSize()
+
+	lno := base.Pos
+	if pos := t.Pos(); pos.IsKnown() {
+		base.Pos = pos
+	}
+
+	t.Width = -2
+	t.Align = 0 // 0 means use t.Width, below
+
+	et := t.Kind()
+	switch et {
+	case TFUNC, TCHAN, TMAP, TSTRING:
+		break
+
+	// simtype == 0 during bootstrap
+	default:
+		if SimType[t.Kind()] != 0 {
+			et = SimType[t.Kind()]
+		}
+	}
+
+	var w int64
+	switch et {
+	default:
+		base.Fatalf("dowidth: unknown type: %v", t)
+
+	// compiler-specific stuff
+	case TINT8, TUINT8, TBOOL:
+		// bool is int8
+		w = 1
+
+	case TINT16, TUINT16:
+		w = 2
+
+	case TINT32, TUINT32, TFLOAT32:
+		w = 4
+
+	case TINT64, TUINT64, TFLOAT64:
+		w = 8
+		t.Align = uint8(RegSize)
+
+	case TCOMPLEX64:
+		w = 8
+		t.Align = 4
+
+	case TCOMPLEX128:
+		w = 16
+		t.Align = uint8(RegSize)
+
+	case TPTR:
+		w = int64(PtrSize)
+		CheckSize(t.Elem())
+
+	case TUNSAFEPTR:
+		w = int64(PtrSize)
+
+	case TINTER: // implemented as 2 pointers
+		w = 2 * int64(PtrSize)
+		t.Align = uint8(PtrSize)
+		expandiface(t)
+
+	case TCHAN: // implemented as pointer
+		w = int64(PtrSize)
+
+		CheckSize(t.Elem())
+
+		// make fake type to check later to
+		// trigger channel argument check.
+		t1 := NewChanArgs(t)
+		CheckSize(t1)
+
+	case TCHANARGS:
+		t1 := t.ChanArgs()
+		CalcSize(t1) // just in case
+		if t1.Elem().Width >= 1<<16 {
+			base.ErrorfAt(typePos(t1), "channel element type too large (>64kB)")
+		}
+		w = 1 // anything will do
+
+	case TMAP: // implemented as pointer
+		w = int64(PtrSize)
+		CheckSize(t.Elem())
+		CheckSize(t.Key())
+
+	case TFORW: // should have been filled in
+		reportTypeLoop(t)
+		w = 1 // anything will do
+
+	case TANY:
+		// not a real type; should be replaced before use.
+		base.Fatalf("dowidth any")
+
+	case TSTRING:
+		if StringSize == 0 {
+			base.Fatalf("early dowidth string")
+		}
+		w = StringSize
+		t.Align = uint8(PtrSize)
+
+	case TARRAY:
+		if t.Elem() == nil {
+			break
+		}
+
+		CalcSize(t.Elem())
+		if t.Elem().Width != 0 {
+			cap := (uint64(MaxWidth) - 1) / uint64(t.Elem().Width)
+			if uint64(t.NumElem()) > cap {
+				base.ErrorfAt(typePos(t), "type %L larger than address space", t)
+			}
+		}
+		w = t.NumElem() * t.Elem().Width
+		t.Align = t.Elem().Align
+
+	case TSLICE:
+		if t.Elem() == nil {
+			break
+		}
+		w = SliceSize
+		CheckSize(t.Elem())
+		t.Align = uint8(PtrSize)
+
+	case TSTRUCT:
+		if t.IsFuncArgStruct() {
+			base.Fatalf("dowidth fn struct %v", t)
+		}
+		w = calcStructOffset(t, t, 0, 1)
+
+	// make fake type to check later to
+	// trigger function argument computation.
+	case TFUNC:
+		t1 := NewFuncArgs(t)
+		CheckSize(t1)
+		w = int64(PtrSize) // width of func type is pointer
+
+	// function is 3 cated structures;
+	// compute their widths as side-effect.
+	case TFUNCARGS:
+		t1 := t.FuncArgs()
+		w = calcStructOffset(t1, t1.Recvs(), 0, 0)
+		w = calcStructOffset(t1, t1.Params(), w, RegSize)
+		w = calcStructOffset(t1, t1.Results(), w, RegSize)
+		t1.Extra.(*Func).Argwid = w
+		if w%int64(RegSize) != 0 {
+			base.Warn("bad type %v %d\n", t1, w)
+		}
+		t.Align = 1
+	}
+
+	if PtrSize == 4 && w != int64(int32(w)) {
+		base.ErrorfAt(typePos(t), "type %v too large", t)
+	}
+
+	t.Width = w
+	if t.Align == 0 {
+		if w == 0 || w > 8 || w&(w-1) != 0 {
+			base.Fatalf("invalid alignment for %v", t)
+		}
+		t.Align = uint8(w)
+	}
+
+	base.Pos = lno
+
+	ResumeCheckSize()
+}
+
+// CalcStructSize calculates the size of s,
+// filling in s.Width and s.Align,
+// even if size calculation is otherwise disabled.
+func CalcStructSize(s *Type) {
+	s.Width = calcStructOffset(s, s, 0, 1) // sets align
+}
+
+// when a type's width should be known, we call checkwidth
+// to compute it.  during a declaration like
+//
+//	type T *struct { next T }
+//
+// it is necessary to defer the calculation of the struct width
+// until after T has been initialized to be a pointer to that struct.
+// similarly, during import processing structs may be used
+// before their definition.  in those situations, calling
+// defercheckwidth() stops width calculations until
+// resumecheckwidth() is called, at which point all the
+// checkwidths that were deferred are executed.
+// dowidth should only be called when the type's size
+// is needed immediately.  checkwidth makes sure the
+// size is evaluated eventually.
+
+var deferredTypeStack []*Type
+
+func CheckSize(t *Type) {
+	if t == nil {
+		return
+	}
+
+	// function arg structs should not be checked
+	// outside of the enclosing function.
+	if t.IsFuncArgStruct() {
+		base.Fatalf("checkwidth %v", t)
+	}
+
+	if defercalc == 0 {
+		CalcSize(t)
+		return
+	}
+
+	// if type has not yet been pushed on deferredTypeStack yet, do it now
+	if !t.Deferwidth() {
+		t.SetDeferwidth(true)
+		deferredTypeStack = append(deferredTypeStack, t)
+	}
+}
+
+func DeferCheckSize() {
+	defercalc++
+}
+
+func ResumeCheckSize() {
+	if defercalc == 1 {
+		for len(deferredTypeStack) > 0 {
+			t := deferredTypeStack[len(deferredTypeStack)-1]
+			deferredTypeStack = deferredTypeStack[:len(deferredTypeStack)-1]
+			t.SetDeferwidth(false)
+			CalcSize(t)
+		}
+	}
+
+	defercalc--
+}
+
+// PtrDataSize returns the length in bytes of the prefix of t
+// containing pointer data. Anything after this offset is scalar data.
+func PtrDataSize(t *Type) int64 {
+	if !t.HasPointers() {
+		return 0
+	}
+
+	switch t.Kind() {
+	case TPTR,
+		TUNSAFEPTR,
+		TFUNC,
+		TCHAN,
+		TMAP:
+		return int64(PtrSize)
+
+	case TSTRING:
+		// struct { byte *str; intgo len; }
+		return int64(PtrSize)
+
+	case TINTER:
+		// struct { Itab *tab;	void *data; } or
+		// struct { Type *type; void *data; }
+		// Note: see comment in plive.go:onebitwalktype1.
+		return 2 * int64(PtrSize)
+
+	case TSLICE:
+		// struct { byte *array; uintgo len; uintgo cap; }
+		return int64(PtrSize)
+
+	case TARRAY:
+		// haspointers already eliminated t.NumElem() == 0.
+		return (t.NumElem()-1)*t.Elem().Width + PtrDataSize(t.Elem())
+
+	case TSTRUCT:
+		// Find the last field that has pointers.
+		var lastPtrField *Field
+		for _, t1 := range t.Fields().Slice() {
+			if t1.Type.HasPointers() {
+				lastPtrField = t1
+			}
+		}
+		return lastPtrField.Offset + PtrDataSize(lastPtrField.Type)
+
+	default:
+		base.Fatalf("typeptrdata: unexpected type, %v", t)
+		return 0
+	}
+}