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cmd/compile: inline _, ok = i.(T)

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We already inlined

_, ok = e.(T)
_, ok = i.(E)
_, ok = e.(E)

The only ok-only variants not inlined are now

_, ok = i.(I)
_, ok = e.(I)

These call getitab, so are non-trivial.

Change-Id: Ie45fd8933ee179a679b92ce925079b94cff0ee12
Reviewed-on: https://go-review.googlesource.com/26658
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Josh Bleecher Snyder 2016-06-06 08:29:52 -07:00
parent e6e26eeb29
commit 562d06fc23
4 changed files with 36 additions and 25 deletions
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10
src/cmd/compile/internal/gc/subr.go
View file

@ -2317,6 +2317,16 @@ func isdirectiface(t *Type) bool {
return false
}
// itabType loads the _type field from a runtime.itab struct.
func itabType(itab *Node) *Node {
typ := NodSym(ODOTPTR, itab, nil)
typ.Type = Ptrto(Types[TUINT8])
typ.Typecheck = 1
typ.Xoffset = int64(Widthptr) // offset of _type in runtime.itab
typ.Bounded = true // guaranteed not to fault
return typ
}
// iet returns 'T' if t is a concrete type,
// 'I' if t is an interface type, and 'E' if t is an empty interface type.
// It is used to build calls to the conv* and assert* runtime routines.

6
src/cmd/compile/internal/gc/swt.go
View file

@ -589,11 +589,7 @@ func (s *typeSwitch) walk(sw *Node) {
if !cond.Right.Type.IsEmptyInterface() {
// Load type from itab.
typ = NodSym(ODOTPTR, typ, nil)
typ.Type = Ptrto(Types[TUINT8])
typ.Typecheck = 1
typ.Xoffset = int64(Widthptr) // offset of _type in runtime.itab
typ.Bounded = true // guaranteed not to fault
typ = itabType(typ)
}
// Load hash from type.
h := NodSym(ODOTPTR, typ, nil)

30
src/cmd/compile/internal/gc/walk.go
View file

@ -960,19 +960,27 @@ opswitch:
fromKind := from.Type.iet()
toKind := t.iet()
res := n.List.First()
// Avoid runtime calls in a few cases of the form _, ok := i.(T).
// This is faster and shorter and allows the corresponding assertX2X2
// routines to skip nil checks on their last argument.
if isblank(n.List.First()) {
if isblank(res) {
var fast *Node
switch {
case fromKind == 'E' && toKind == 'T':
tab := Nod(OITAB, from, nil) // type:eface::tab:iface
typ := Nod(OCONVNOP, typename(t), nil)
typ.Type = Ptrto(Types[TUINTPTR])
fast = Nod(OEQ, tab, typ)
case fromKind == 'I' && toKind == 'E',
fromKind == 'E' && toKind == 'E':
switch toKind {
case 'T':
tab := Nod(OITAB, from, nil)
if fromKind == 'E' {
typ := Nod(OCONVNOP, typename(t), nil)
typ.Type = Ptrto(Types[TUINTPTR])
fast = Nod(OEQ, tab, typ)
break
}
fast = Nod(OANDAND,
Nod(ONE, nodnil(), tab),
Nod(OEQ, itabType(tab), typename(t)),
)
case 'E':
tab := Nod(OITAB, from, nil)
fast = Nod(ONE, nodnil(), tab)
}
@ -987,10 +995,10 @@ opswitch:
}
var resptr *Node // &res
if isblank(n.List.First()) {
if isblank(res) {
resptr = nodnil()
} else {
resptr = Nod(OADDR, n.List.First(), nil)
resptr = Nod(OADDR, res, nil)
}
resptr.Etype = 1 // addr does not escape

15
src/runtime/iface.go
View file

@ -218,20 +218,17 @@ func assertI2T(t *_type, i iface, r unsafe.Pointer) {
}
}
// The compiler ensures that r is non-nil.
func assertI2T2(t *_type, i iface, r unsafe.Pointer) bool {
tab := i.tab
if tab == nil || tab._type != t {
if r != nil {
memclr(r, t.size)
}
memclr(r, t.size)
return false
}
if r != nil {
if isDirectIface(t) {
writebarrierptr((*uintptr)(r), uintptr(i.data))
} else {
typedmemmove(t, r, i.data)
}
if isDirectIface(t) {
writebarrierptr((*uintptr)(r), uintptr(i.data))
} else {
typedmemmove(t, r, i.data)
}
return true
}