2 files changed, 72 insertions, 4 deletions

diff --git a/src/cmd/compile/internal/ssa/schedule.go b/src/cmd/compile/internal/ssa/schedule.go
index f2a89d82d8..a455a9a399 100644
--- a/src/cmd/compile/internal/ssa/schedule.go
+++ b/src/cmd/compile/internal/ssa/schedule.go
@@ -14,6 +14,7 @@ const (
 	ScoreMemory
 	ScoreDefault
 	ScoreFlags
+	ScoreSelectCall
 	ScoreControl // towards bottom of block
 )
 
@@ -110,10 +111,25 @@ func schedule(f *Func) {
 				// We want all the vardefs next.
 				score[v.ID] = ScoreVarDef
 			case v.Type.IsMemory():
-				// Schedule stores as early as possible. This tends to
-				// reduce register pressure. It also helps make sure
-				// VARDEF ops are scheduled before the corresponding LEA.
-				score[v.ID] = ScoreMemory
+				// Don't schedule independent operations after call to those functions.
+				// runtime.selectgo will jump to next instruction after this call,
+				// causing extra execution of those operations. Prevent it, by setting
+				// priority to high value.
+				if (v.Op == OpAMD64CALLstatic || v.Op == OpPPC64CALLstatic ||
+					v.Op == OpARMCALLstatic || v.Op == OpARM64CALLstatic ||
+					v.Op == Op386CALLstatic || v.Op == OpMIPS64CALLstatic ||
+					v.Op == OpS390XCALLstatic || v.Op == OpMIPSCALLstatic) &&
+					(isSameSym(v.Aux, "runtime.selectrecv") ||
+						isSameSym(v.Aux, "runtime.selectrecv2") ||
+						isSameSym(v.Aux, "runtime.selectsend") ||
+						isSameSym(v.Aux, "runtime.selectdefault")) {
+					score[v.ID] = ScoreSelectCall
+				} else {
+					// Schedule stores as early as possible. This tends to
+					// reduce register pressure. It also helps make sure
+					// VARDEF ops are scheduled before the corresponding LEA.
+					score[v.ID] = ScoreMemory
+				}
 			case v.Op == OpSelect0 || v.Op == OpSelect1:
 				// Schedule the pseudo-op of reading part of a tuple
 				// immediately after the tuple-generating op, since
diff --git a/test/fixedbugs/issue19201.go b/test/fixedbugs/issue19201.go
new file mode 100644
index 0000000000..e370d55df1
--- /dev/null
+++ b/test/fixedbugs/issue19201.go
@@ -0,0 +1,52 @@
+// run
+
+// Copyright 2017 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 main
+
+import (
+	"encoding/binary"
+)
+
+var (
+	ch1 = make(chan int)
+	ch2 = make(chan int)
+
+	bin  = []byte("a\000\000\001")
+	want = binary.BigEndian.Uint32(bin)
+
+	c consumer = noopConsumer{}
+)
+
+type msg struct {
+	code uint32
+}
+
+type consumer interface {
+	consume(msg)
+}
+
+type noopConsumer struct{}
+
+func (noopConsumer) consume(msg) {}
+
+func init() {
+	close(ch1)
+}
+
+func main() {
+	var m msg
+	m.code = binary.BigEndian.Uint32(bin)
+
+	select {
+	case <-ch1:
+		c.consume(m)
+		if m.code != want {
+			// can not use m.code here, or it will work
+			panic("BigEndian read failed")
+		}
+	case <-ch2:
+	}
+}