/
align.go
399 lines (336 loc) · 8.04 KB
/
align.go
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// 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 gc
// 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 {
Fatalf("rnd %d", r)
}
return (o + r - 1) &^ (r - 1)
}
func offmod(t *Type) {
o := int32(0)
for _, f := range t.Fields().Slice() {
f.Offset = int64(o)
o += int32(Widthptr)
if int64(o) >= Thearch.MAXWIDTH {
Yyerror("interface too large")
o = int32(Widthptr)
}
}
}
func widstruct(errtype *Type, t *Type, o int64, flag int) int64 {
starto := o
maxalign := int32(flag)
if maxalign < 1 {
maxalign = 1
}
lastzero := int64(0)
var w int64
for _, f := range t.Fields().Slice() {
if f.Type == nil {
// broken field, just skip it so that other valid fields
// get a width.
continue
}
dowidth(f.Type)
if int32(f.Type.Align) > maxalign {
maxalign = int32(f.Type.Align)
}
if f.Type.Width < 0 {
Fatalf("invalid width %d", f.Type.Width)
}
w = f.Type.Width
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.
if f.Nname.Name.Param.Stackcopy != nil {
f.Nname.Name.Param.Stackcopy.Xoffset = o
f.Nname.Xoffset = 0
} else {
f.Nname.Xoffset = o
}
}
if w == 0 {
lastzero = o
}
o += w
if o >= Thearch.MAXWIDTH {
Yyerror("type %v too large", Tconv(errtype, FmtLong))
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
}
func dowidth(t *Type) {
if Widthptr == 0 {
Fatalf("dowidth without betypeinit")
}
if t == nil {
return
}
if t.Width > 0 {
if t.Align == 0 {
// See issue 11354
Fatalf("zero alignment with nonzero size %v", t)
}
return
}
if t.Width == -2 {
if !t.Broke {
t.Broke = true
yyerrorl(t.Lineno, "invalid recursive type %v", t)
}
t.Width = 0
return
}
// 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
defercalc++
lno := lineno
lineno = t.Lineno
t.Width = -2
t.Align = 0
et := t.Etype
switch et {
case TFUNC, TCHAN, TMAP, TSTRING:
break
// simtype == 0 during bootstrap
default:
if Simtype[t.Etype] != 0 {
et = Simtype[t.Etype]
}
}
w := int64(0)
switch et {
default:
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, TCOMPLEX64:
w = 8
t.Align = uint8(Widthreg)
case TCOMPLEX128:
w = 16
t.Align = uint8(Widthreg)
case TPTR32:
w = 4
checkwidth(t.Elem())
case TPTR64:
w = 8
checkwidth(t.Elem())
case TUNSAFEPTR:
w = int64(Widthptr)
case TINTER: // implemented as 2 pointers
w = 2 * int64(Widthptr)
t.Align = uint8(Widthptr)
offmod(t)
case TCHAN: // implemented as pointer
w = int64(Widthptr)
checkwidth(t.Elem())
// make fake type to check later to
// trigger channel argument check.
t1 := typChanArgs(t)
checkwidth(t1)
case TCHANARGS:
t1 := t.ChanArgs()
dowidth(t1) // just in case
if t1.Elem().Width >= 1<<16 {
Yyerror("channel element type too large (>64kB)")
}
t.Width = 1
case TMAP: // implemented as pointer
w = int64(Widthptr)
checkwidth(t.Val())
checkwidth(t.Key())
case TFORW: // should have been filled in
if !t.Broke {
Yyerror("invalid recursive type %v", t)
}
w = 1 // anything will do
// dummy type; should be replaced before use.
case TANY:
if Debug['A'] == 0 {
Fatalf("dowidth any")
}
w = 1 // anything will do
case TSTRING:
if sizeof_String == 0 {
Fatalf("early dowidth string")
}
w = int64(sizeof_String)
t.Align = uint8(Widthptr)
case TARRAY:
if t.Elem() == nil {
break
}
if t.isDDDArray() {
if !t.Broke {
Yyerror("use of [...] array outside of array literal")
t.Broke = true
}
break
}
dowidth(t.Elem())
if t.Elem().Width != 0 {
cap := (uint64(Thearch.MAXWIDTH) - 1) / uint64(t.Elem().Width)
if uint64(t.NumElem()) > cap {
Yyerror("type %v larger than address space", Tconv(t, FmtLong))
}
}
w = t.NumElem() * t.Elem().Width
t.Align = t.Elem().Align
case TSLICE:
if t.Elem() == nil {
break
}
w = int64(sizeof_Array)
checkwidth(t.Elem())
t.Align = uint8(Widthptr)
case TSTRUCT:
if t.IsFuncArgStruct() {
Fatalf("dowidth fn struct %v", t)
}
w = widstruct(t, t, 0, 1)
// make fake type to check later to
// trigger function argument computation.
case TFUNC:
t1 := typFuncArgs(t)
checkwidth(t1)
w = int64(Widthptr) // width of func type is pointer
// function is 3 cated structures;
// compute their widths as side-effect.
case TFUNCARGS:
t1 := t.FuncArgs()
w = widstruct(t1, t1.Recvs(), 0, 0)
w = widstruct(t1, t1.Params(), w, Widthreg)
w = widstruct(t1, t1.Results(), w, Widthreg)
t1.Extra.(*FuncType).Argwid = w
if w%int64(Widthreg) != 0 {
Warn("bad type %v %d\n", t1, w)
}
t.Align = 1
}
if Widthptr == 4 && w != int64(int32(w)) {
Yyerror("type %v too large", t)
}
t.Width = w
if t.Align == 0 {
if w > 8 || w&(w-1) != 0 {
Fatalf("invalid alignment for %v", t)
}
t.Align = uint8(w)
}
lineno = lno
if defercalc == 1 {
resumecheckwidth()
} else {
defercalc--
}
}
// 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 checkwidth(t *Type) {
if t == nil {
return
}
// function arg structs should not be checked
// outside of the enclosing function.
if t.IsFuncArgStruct() {
Fatalf("checkwidth %v", t)
}
if defercalc == 0 {
dowidth(t)
return
}
if t.Deferwidth {
return
}
t.Deferwidth = true
deferredTypeStack = append(deferredTypeStack, t)
}
func defercheckwidth() {
// we get out of sync on syntax errors, so don't be pedantic.
if defercalc != 0 && nerrors == 0 {
Fatalf("defercheckwidth")
}
defercalc = 1
}
func resumecheckwidth() {
if defercalc == 0 {
Fatalf("resumecheckwidth")
}
for len(deferredTypeStack) > 0 {
t := deferredTypeStack[len(deferredTypeStack)-1]
deferredTypeStack = deferredTypeStack[:len(deferredTypeStack)-1]
t.Deferwidth = false
dowidth(t)
}
defercalc = 0
}
// compute total size of f's in/out arguments.
func Argsize(t *Type) int {
var w int64
for _, p := range recvsParamsResults {
for _, f := range p(t).Fields().Slice() {
if x := f.End(); x > w {
w = x
}
}
}
w = Rnd(w, int64(Widthptr))
if int64(int(w)) != w {
Fatalf("argsize too big")
}
return int(w)
}