The additions were machine-generated.

The change for x * 7 avoids a reg-reg move,
reducing the number of instructions from 3 to 2.

Change-Id: Ib002e39f29ca5e46cfdb8daaf87ddc7ba50a17e5
Reviewed-on: https://go-review.googlesource.com/102395
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>