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cmd/compile, etc: use name for type pkgPath

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By replacing the *string used to represent pkgPath with a
reflect.name everywhere, the embedded *string for package paths
inside the reflect.name can be replaced by an offset, nameOff.
This reduces the number of pointers in the type information.

This also moves all reflect.name types into the same section, making
it possible to use nameOff more widely in later CLs.

No significant binary size change for normal binaries, but:

linux/amd64 PIE:
	cmd/go: -440KB (3.7%)
	jujud:  -2.6MB (3.2%)

For #6853.

Change-Id: I3890b132a784a1090b1b72b32febfe0bea77eaee
Reviewed-on: https://go-review.googlesource.com/21395
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
David Crawshaw 2016-03-31 10:02:10 -04:00
parent 73e2ad2022
commit f120936dff
7 changed files with 169 additions and 114 deletions
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64
src/reflect/type.go
View file

@ -299,9 +299,9 @@ type method struct {
// Using a pointer to this struct reduces the overall size required
// to describe an unnamed type with no methods.
type uncommonType struct {
pkgPath *string // import path; nil for built-in types like int, string
mcount uint16 // number of methods
moff uint16 // offset from this uncommontype to [mcount]method
pkgPath name // import path; empty for built-in types like int, string
mcount uint16 // number of methods
moff uint16 // offset from this uncommontype to [mcount]method
}
// ChanDir represents a channel type's direction.
@ -354,7 +354,7 @@ type imethod struct {
// interfaceType represents an interface type.
type interfaceType struct {
rtype `reflect:"interface"`
pkgPath *string // import path
pkgPath name // import path
methods []imethod // sorted by hash
}
@ -396,7 +396,7 @@ type structField struct {
// structType represents a struct type.
type structType struct {
rtype `reflect:"struct"`
pkgPath *string
pkgPath name
fields []structField // sorted by offset
}
@ -406,7 +406,7 @@ type structType struct {
//
// 1<<0 the name is exported
// 1<<1 tag data follows the name
// 1<<2 pkgPath *string follow the name and tag
// 1<<2 pkgPath nameOff follows the name and tag
//
// The next two bytes are the data length:
//
@ -417,10 +417,9 @@ type structType struct {
// If tag data follows then bytes 3+l and 3+l+1 are the tag length,
// with the data following.
//
// If the import path follows, then ptrSize bytes at the end of
// the data form a *string. The pointer is aligned to its width.
// The import path is only set for concrete methods that are defined
// in a different package than their type.
// If the import path follows, then 4 bytes at the end of
// the data form a nameOff. The import path is only set for concrete
// methods that are defined in a different package than their type.
type name struct {
bytes *byte
}
@ -446,6 +445,9 @@ func (n *name) tagLen() int {
}
func (n *name) name() (s string) {
if n.bytes == nil {
return ""
}
nl := n.nameLen()
if nl == 0 {
return ""
@ -468,16 +470,18 @@ func (n *name) tag() (s string) {
return s
}
func (n *name) pkgPath() *string {
if *n.data(0)&(1<<2) == 0 {
return nil
func (n *name) pkgPath() string {
if n.bytes == nil || *n.data(0)&(1<<2) == 0 {
return ""
}
off := 3 + n.nameLen()
if tl := n.tagLen(); tl > 0 {
off += 2 + tl
}
off = int(round(uintptr(off), ptrSize))
return *(**string)(unsafe.Pointer(n.data(off)))
var nameOff int32
copy((*[4]byte)(unsafe.Pointer(&nameOff))[:], (*[4]byte)(unsafe.Pointer(n.data(off)))[:])
pkgPathName := name{(*byte)(resolveTypeOff(unsafe.Pointer(n), nameOff))}
return pkgPathName.name()
}
// round n up to a multiple of a. a must be a power of 2.
@ -595,10 +599,10 @@ func (t *uncommonType) methods() []method {
}
func (t *uncommonType) PkgPath() string {
if t == nil || t.pkgPath == nil {
if t == nil {
return ""
}
return *t.pkgPath
return t.pkgPath.name()
}
// resolveTypeOff resolves an *rtype offset from a base type.
@ -752,11 +756,10 @@ func (t *rtype) Method(i int) (m Method) {
m.Name = p.name.name()
fl := flag(Func)
if !p.name.isExported() {
pkgPath := p.name.pkgPath()
if pkgPath == nil {
pkgPath = ut.pkgPath
m.PkgPath = p.name.pkgPath()
if m.PkgPath == "" {
m.PkgPath = ut.pkgPath.name()
}
m.PkgPath = *pkgPath
fl |= flagStickyRO
}
if p.mtyp != 0 {
@ -1004,11 +1007,10 @@ func (t *interfaceType) Method(i int) (m Method) {
p := &t.methods[i]
m.Name = p.name.name()
if !p.name.isExported() {
pkgPath := p.name.pkgPath()
if pkgPath == nil {
pkgPath = t.pkgPath
m.PkgPath = p.name.pkgPath()
if m.PkgPath == "" {
m.PkgPath = t.pkgPath.name()
}
m.PkgPath = *pkgPath
}
m.Type = toType(p.typ)
m.Index = i
@ -1146,9 +1148,9 @@ func (t *structType) Field(i int) (f StructField) {
f.Name = t.Name()
f.Anonymous = true
}
if t.pkgPath != nil && !p.name.isExported() {
if !p.name.isExported() {
// Fields never have an import path in their name.
f.PkgPath = *t.pkgPath
f.PkgPath = t.pkgPath.name()
}
if tag := p.name.tag(); tag != "" {
f.Tag = StructTag(tag)
@ -2325,7 +2327,7 @@ func StructOf(fields []StructField) Type {
case Interface:
ift := (*interfaceType)(unsafe.Pointer(ft))
for im, m := range ift.methods {
if m.name.pkgPath() != nil {
if m.name.pkgPath() != "" {
// TODO(sbinet)
panic("reflect: embedded interface with unexported method(s) not implemented")
}
@ -2384,7 +2386,7 @@ func StructOf(fields []StructField) Type {
ptr := (*ptrType)(unsafe.Pointer(ft))
if unt := ptr.uncommon(); unt != nil {
for _, m := range unt.methods() {
if m.name.pkgPath() != nil {
if m.name.pkgPath() != "" {
// TODO(sbinet)
panic("reflect: embedded interface with unexported method(s) not implemented")
}
@ -2398,7 +2400,7 @@ func StructOf(fields []StructField) Type {
}
if unt := ptr.elem.uncommon(); unt != nil {
for _, m := range unt.methods() {
if m.name.pkgPath() != nil {
if m.name.pkgPath() != "" {
// TODO(sbinet)
panic("reflect: embedded interface with unexported method(s) not implemented")
}
@ -2413,7 +2415,7 @@ func StructOf(fields []StructField) Type {
default:
if unt := ft.uncommon(); unt != nil {
for _, m := range unt.methods() {
if m.name.pkgPath() != nil {
if m.name.pkgPath() != "" {
// TODO(sbinet)
panic("reflect: embedded interface with unexported method(s) not implemented")
}