cmd/compile: add a test for reproducible build with anonymous interfaces

Duplicated anonymous interfaces caused nondeterministic build.
The fix is CL 129515. This CL adds a test.

Updates #27013.

Change-Id: I6b7e1bbfc943c22e8e6f32c145f7aebb567cef15
Reviewed-on: https://go-review.googlesource.com/129680
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/compile/internal/gc/reproduciblebuilds_test.go

@@ -15,11 +15,20 @@ import (
 )
 
 func TestReproducibleBuilds(t *testing.T) {
+	tests := []string{
+		"issue20272.go",
+		"issue27013.go",
+	}
+
 	testenv.MustHaveGoBuild(t)
 	iters := 10
 	if testing.Short() {
 		iters = 4
 	}
+	t.Parallel()
+	for _, test := range tests {
+		test := test
+		t.Run(test, func(t *testing.T) {
 			t.Parallel()
 			var want []byte
 			tmp, err := ioutil.TempFile("", "")
@@ -29,7 +38,7 @@ func TestReproducibleBuilds(t *testing.T) {
 			defer os.Remove(tmp.Name())
 			defer tmp.Close()
 			for i := 0; i < iters; i++ {
-		out, err := exec.Command(testenv.GoToolPath(t), "tool", "compile", "-o", tmp.Name(), filepath.Join("testdata", "reproducible", "issue20272.go")).CombinedOutput()
+				out, err := exec.Command(testenv.GoToolPath(t), "tool", "compile", "-o", tmp.Name(), filepath.Join("testdata", "reproducible", test)).CombinedOutput()
 				if err != nil {
 					t.Fatalf("failed to compile: %v\n%s", err, out)
 				}
@@ -45,4 +54,6 @@ func TestReproducibleBuilds(t *testing.T) {
 					}
 				}
 			}
+		})
+	}
 }

src/cmd/compile/internal/gc/testdata/reproducible/issue27013.go

+// Copyright 2018 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 p
+
+func A(arg interface{}) {
+	_ = arg.(interface{ Func() int32 })
+	_ = arg.(interface{ Func() int32 })
+	_ = arg.(interface{ Func() int32 })
+	_ = arg.(interface{ Func() int32 })
+	_ = arg.(interface{ Func() int32 })
+	_ = arg.(interface{ Func() int32 })
+	_ = arg.(interface{ Func() int32 })
+}