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

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>

1 files changed, 6 insertions, 9 deletions

diff --git a/src/runtime/iface.go b/src/runtime/iface.go
index 1690147fac..7f24a6e69c 100644
--- a/src/runtime/iface.go
+++ b/src/runtime/iface.go
@@ -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
 }