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cmd/compile, runtime: new static name encoding

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Create a byte encoding designed for static Go names.

It is intended to be a compact representation of a name
and optional tag data that can be turned into a Go string
without allocating, and describes whether or not it is
exported without unicode table.

The encoding is described in reflect/type.go:

// The first byte is a bit field containing:
//
//	1<<0 the name is exported
//	1<<1 tag data follows the name
//	1<<2 pkgPath *string follow the name and tag
//
// The next two bytes are the data length:
//
//	 l := uint16(data[1])<<8 | uint16(data[2])
//
// Bytes [3:3+l] are the string data.
//
// 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 import path is only set for concrete
// methods that are defined in a different package than their type.

Shrinks binary sizes:

	cmd/go: 164KB (1.6%)
	jujud:  1.0MB (1.5%)

For #6853.

Change-Id: I46b6591015b17936a443c9efb5009de8dfe8b609
Reviewed-on: https://go-review.googlesource.com/20968
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 2016-03-21 13:21:55 -04:00
parent 0a82ed5d7c
commit 24ce64d1a9
6 changed files with 387 additions and 138 deletions
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8
src/reflect/value.go
View file

@ -554,7 +554,7 @@ func methodReceiver(op string, v Value, methodIndex int) (rcvrtype, t *rtype, fn
panic("reflect: internal error: invalid method index")
}
m := &tt.methods[i]
if m.pkgPath != nil {
if !m.name.isExported() {
panic("reflect: " + op + " of unexported method")
}
iface := (*nonEmptyInterface)(v.ptr)
@ -571,7 +571,7 @@ func methodReceiver(op string, v Value, methodIndex int) (rcvrtype, t *rtype, fn
panic("reflect: internal error: invalid method index")
}
m := &ut.methods[i]
if m.pkgPath != nil {
if !m.name.isExported() {
panic("reflect: " + op + " of unexported method")
}
fn = unsafe.Pointer(&m.ifn)
@ -750,8 +750,8 @@ func (v Value) Field(i int) Value {
// Inherit permission bits from v, but clear flagEmbedRO.
fl := v.flag&(flagStickyRO|flagIndir|flagAddr) | flag(typ.Kind())
// Using an unexported field forces flagRO.
if field.pkgPath != nil {
if field.name == nil {
if !field.name.isExported() {
if field.name.name() == "" {
fl |= flagEmbedRO
} else {
fl |= flagStickyRO