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cmd/compile: remove rtype.ptrToThis

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Simplifies some code as ptrToThis was unreliable under dynamic
linking. Now the same type lookup is used regardless of execution
mode.

A synthetic relocation, R_USETYPE, is introduced to make sure the
linker includes *T on use of T, if *T is carrying methods.

Changes the heap dump format. Anything reading the format needs to
look at the last bool of a type of an interface value to determine
if the type should be the pointer-to type.

Reduces binary size of cmd/go by 0.2%.
For #6853.

Change-Id: I79fcb19a97402bdb0193f3c7f6d94ddf061ee7b2
Reviewed-on: https://go-review.googlesource.com/19695
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
David Crawshaw 2016-02-18 06:31:57 -05:00
parent 5abd327d00
commit 30f93f0994
6 changed files with 30 additions and 72 deletions
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20
src/reflect/type.go
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@ -256,7 +256,6 @@ type rtype struct {
gcdata *byte // garbage collection data
string string // string form; unnecessary but undeniably useful
*uncommonType // (relatively) uncommon fields
ptrToThis *rtype // type for pointer to this type, if used in binary or has methods
}
// a copy of runtime.typeAlg
@ -1030,15 +1029,7 @@ func PtrTo(t Type) Type {
}
func (t *rtype) ptrTo() *rtype {
if p := t.ptrToThis; p != nil {
return p
}
// Otherwise, synthesize one.
// This only happens for pointers with no methods.
// We keep the mapping in a map on the side, because
// this operation is rare and a separate map lets us keep
// the type structures in read-only memory.
// Check the cache.
ptrMap.RLock()
if m := ptrMap.m; m != nil {
if p := m[t]; p != nil {
@ -1047,6 +1038,7 @@ func (t *rtype) ptrTo() *rtype {
}
}
ptrMap.RUnlock()
ptrMap.Lock()
if ptrMap.m == nil {
ptrMap.m = make(map[*rtype]*ptrType)
@ -1086,7 +1078,6 @@ func (t *rtype) ptrTo() *rtype {
p.hash = fnv1(t.hash, '*')
p.uncommonType = nil
p.ptrToThis = nil
p.elem = t
ptrMap.m[t] = p
@ -1310,7 +1301,7 @@ func haveIdenticalUnderlyingType(T, V *rtype) bool {
// Note that strings are not unique identifiers for types:
// there can be more than one with a given string.
// Only types we might want to look up are included:
// channels, maps, slices, and arrays.
// pointers, channels, maps, slices, and arrays.
func typelinks() [][]*rtype
// typesByString returns the subslice of typelinks() whose elements have
@ -1465,7 +1456,6 @@ func ChanOf(dir ChanDir, t Type) Type {
ch.hash = fnv1(typ.hash, 'c', byte(dir))
ch.elem = typ
ch.uncommonType = nil
ch.ptrToThis = nil
return cachePut(ckey, &ch.rtype)
}
@ -1528,7 +1518,6 @@ func MapOf(key, elem Type) Type {
mt.reflexivekey = isReflexive(ktyp)
mt.needkeyupdate = needKeyUpdate(ktyp)
mt.uncommonType = nil
mt.ptrToThis = nil
return cachePut(ckey, &mt.rtype)
}
@ -1607,7 +1596,6 @@ func FuncOf(in, out []Type, variadic bool) Type {
// Populate the remaining fields of ft and store in cache.
ft.string = str
ft.uncommonType = nil
ft.ptrToThis = nil
funcLookupCache.m[hash] = append(funcLookupCache.m[hash], &ft.rtype)
return &ft.rtype
@ -1837,7 +1825,6 @@ func SliceOf(t Type) Type {
slice.hash = fnv1(typ.hash, '[')
slice.elem = typ
slice.uncommonType = nil
slice.ptrToThis = nil
return cachePut(ckey, &slice.rtype)
}
@ -1895,7 +1882,6 @@ func ArrayOf(count int, elem Type) Type {
array.align = typ.align
array.fieldAlign = typ.fieldAlign
array.uncommonType = nil
array.ptrToThis = nil
array.len = uintptr(count)
array.slice = slice.(*rtype)