Local variables can also be relied on the be 64-bit aligned, since
they will be escaped to the heap if used with any atomic operations.
Also, allocated arrays are also aligned, just like structs and slices.
Fixes #18955.
Change-Id: I8a1897f6ff78922c8bfcf20d6eb4bcb17a70ba2d
Reviewed-on: https://go-review.googlesource.com/48112
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
// On non-Linux ARM, the 64-bit functions use instructions unavailable before the ARMv6k core.
//
// On both ARM and x86-32, it is the caller's responsibility to arrange for 64-bit
-// alignment of 64-bit words accessed atomically. The first word in a global
-// variable or in an allocated struct or slice can be relied upon to be
+// alignment of 64-bit words accessed atomically. The first word in a
+// variable or in an allocated struct, array, or slice can be relied upon to be
// 64-bit aligned.
// SwapInt32 atomically stores new into *addr and returns the previous *addr value.