test: check that unaligned load-add opcodes work.

A test for CL 102036.

Change-Id: Ief6dcb4f478670813fbe22ea75a06815a4b201a3
Reviewed-on: https://go-review.googlesource.com/105875
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

test/align.go

+// run
+
+// 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 main
+
+// On 32-bit archs, one of the f fields of a [2]T
+// will be unaligned (address of 4 mod 8).
+// Make sure we can access the f fields successfully,
+// particularly for load-add combo instructions
+// introduced by CL 102036.
+type T struct {
+	pad uint32
+	f float64
+}
+
+//go:noinline
+func f(t, u *T) float64 {
+	return 3.0 + t.f + u.f
+}
+
+func main() {
+	t := [2]T{{0, 1.0}, {0, 2.0}}
+	sink = f(&t[0], &t[1])
+}
+
+var sink float64