runtime: make iface/eface handling more type safe

Change compiler-invoked interface functions to directly take
iface/eface parameters instead of fInterface/interface{} to avoid
needing to always convert.

For the handful of functions that legitimately need to take an
interface{} parameter, add efaceOf to type-safely convert *interface{}
to *eface.

Change-Id: I8928761a12fd3c771394f36adf93d3006a9fcf39
Reviewed-on: https://go-review.googlesource.com/16166
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index 97d5ed2752..d4e3758678 100644
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -82,6 +82,10 @@ type eface struct {
 	data  unsafe.Pointer
 }
 
+func efaceOf(ep *interface{}) *eface {
+	return (*eface)(unsafe.Pointer(ep))
+}
+
 // The guintptr, muintptr, and puintptr are all used to bypass write barriers.
 // It is particularly important to avoid write barriers when the current P has
 // been released, because the GC thinks the world is stopped, and an