[dev.link] Merge branch 'master' into dev.link

2 conflicts, that make sense.
	src/cmd/internal/obj/objfile.go
	src/cmd/link/internal/loader/loader.go

Change-Id: Ib224e2d248cb568fa1e888af79dd908b2f5e05ff

1 files changed, 18 insertions, 2 deletions

diff --git a/src/reflect/value.go b/src/reflect/value.go
index c6f24a5609..a14131e1f8 100644
--- a/src/reflect/value.go
+++ b/src/reflect/value.go
@@ -1553,7 +1553,11 @@ func (v Value) Set(x Value) {
 	}
 	x = x.assignTo("reflect.Set", v.typ, target)
 	if x.flag&flagIndir != 0 {
-		typedmemmove(v.typ, v.ptr, x.ptr)
+		if x.ptr == unsafe.Pointer(&zeroVal[0]) {
+			typedmemclr(v.typ, v.ptr)
+		} else {
+			typedmemmove(v.typ, v.ptr, x.ptr)
+		}
 	} else {
 		*(*unsafe.Pointer)(v.ptr) = x.ptr
 	}
@@ -2360,11 +2364,23 @@ func Zero(typ Type) Value {
 	t := typ.(*rtype)
 	fl := flag(t.Kind())
 	if ifaceIndir(t) {
-		return Value{t, unsafe_New(t), fl | flagIndir}
+		var p unsafe.Pointer
+		if t.size <= maxZero {
+			p = unsafe.Pointer(&zeroVal[0])
+		} else {
+			p = unsafe_New(t)
+		}
+		return Value{t, p, fl | flagIndir}
 	}
 	return Value{t, nil, fl}
 }
 
+// must match declarations in runtime/map.go.
+const maxZero = 1024
+
+//go:linkname zeroVal runtime.zeroVal
+var zeroVal [maxZero]byte
+
 // New returns a Value representing a pointer to a new zero value
 // for the specified type. That is, the returned Value's Type is PtrTo(typ).
 func New(typ Type) Value {