runtime: race instrument read of convT2E/I arg

Sometimes this read is instrumented by compiler when it creates
a temp to take address, but sometimes it is not (e.g. for global vars
compiler takes address of the global directly).

Instrument convT2E/I similarly to chansend and mapaccess.

Fixes #12664

Change-Id: Ia7807f15d735483996426c5f3aed60a33b279579
Reviewed-on: https://go-review.googlesource.com/14752Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/iface.go

@@ -129,6 +129,9 @@ func typ2Itab(t *_type, inter *interfacetype, cache **itab) *itab {
 }
 
 func convT2E(t *_type, elem unsafe.Pointer, x unsafe.Pointer) (e interface{}) {
+	if raceenabled {
+		raceReadObjectPC(t, elem, getcallerpc(unsafe.Pointer(&t)), funcPC(convT2E))
+	}
 	ep := (*eface)(unsafe.Pointer(&e))
 	if isDirectIface(t) {
 		ep._type = t
@@ -147,6 +150,9 @@ func convT2E(t *_type, elem unsafe.Pointer, x unsafe.Pointer) (e interface{}) {
 }
 
 func convT2I(t *_type, inter *interfacetype, cache **itab, elem unsafe.Pointer, x unsafe.Pointer) (i fInterface) {
+	if raceenabled {
+		raceReadObjectPC(t, elem, getcallerpc(unsafe.Pointer(&t)), funcPC(convT2I))
+	}
 	tab := (*itab)(atomicloadp(unsafe.Pointer(cache)))
 	if tab == nil {
 		tab = getitab(inter, t, false)

src/runtime/race/testdata/issue12664_test.go

+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package race_test
+
+import (
+	"fmt"
+	"testing"
+)
+
+var issue12664 = "hi"
+
+func TestRaceIssue12664(t *testing.T) {
+	c := make(chan struct{})
+	go func() {
+		issue12664 = "bye"
+		close(c)
+	}()
+	fmt.Println(issue12664)
+	<-c
+}
+
+type MyI interface {
+	foo()
+}
+
+type MyT int
+
+func (MyT) foo() {
+}
+
+var issue12664_2 MyT = 0
+
+func TestRaceIssue12664_2(t *testing.T) {
+	c := make(chan struct{})
+	go func() {
+		issue12664_2 = 1
+		close(c)
+	}()
+	func(x MyI) {
+		// Never true, but prevents inlining.
+		if x.(MyT) == -1 {
+			close(c)
+		}
+	}(issue12664_2)
+	<-c
+}
+
+var issue12664_3 MyT = 0
+
+func TestRaceIssue12664_3(t *testing.T) {
+	c := make(chan struct{})
+	go func() {
+		issue12664_3 = 1
+		close(c)
+	}()
+	var r MyT
+	var i interface{} = r
+	issue12664_3 = i.(MyT)
+	<-c
+}
+
+var issue12664_4 MyT = 0
+
+func TestRaceIssue12664_4(t *testing.T) {
+	c := make(chan struct{})
+	go func() {
+		issue12664_4 = 1
+		close(c)
+	}()
+	var r MyT
+	var i MyI = r
+	issue12664_4 = i.(MyT)
+	<-c
+}