ARM64 allows for a register to be specified with a return
instruction. While the assembler parsing and encoding currently
supports this, the preprocess function uses LR unconditionally.
Correct this such that if a register is specified, the register
is used.
Change-Id: I708f6c7e910d141559b60d2d5ee76ae2e1dc3a0e
Reviewed-on: https://go-review.googlesource.com/c/go/+/592796 Reviewed-by: Cherry Mui <cherryyz@google.com> Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>