gc: inline append when len<cap
issue 1604
R=rsc, bradfitz
CC=golang-dev
https://golang.org/cl/4313062
diff --git a/src/pkg/runtime/append_test.go b/src/pkg/runtime/append_test.go
new file mode 100644
index 0000000..75a6353
--- /dev/null
+++ b/src/pkg/runtime/append_test.go
@@ -0,0 +1,51 @@
+// Copyright 2011 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 runtime_test
+
+import "testing"
+
+const N = 20
+
+func BenchmarkAppend(b *testing.B) {
+ b.StopTimer()
+ x := make([]int, 0, N)
+ b.StartTimer()
+ for i := 0; i < b.N; i++ {
+ x = x[0:0]
+ for j := 0; j < N; j++ {
+ x = append(x, j)
+ }
+ }
+}
+
+func BenchmarkAppendSpecialCase(b *testing.B) {
+ b.StopTimer()
+ x := make([]int, 0, N)
+ b.StartTimer()
+ for i := 0; i < b.N; i++ {
+ x = x[0:0]
+ for j := 0; j < N; j++ {
+ if len(x) < cap(x) {
+ x = x[:len(x)+1]
+ x[len(x)-1] = j
+ } else {
+ x = append(x, j)
+ }
+ }
+ }
+}
+
+var x = make([]int, 0, 10)
+
+func f() int {
+ x[:1][0] = 3
+ return 2
+}
+
+func TestSideEffectOrder(t *testing.T) {
+ x = append(x, 1, f())
+ if x[0] != 1 || x[1] != 2 {
+ t.Error("append failed: ", x[0], x[1])
+ }
+}
