We need to move the memory variable update back to before endBlock
so that all successors use the right memory value.

See https://go-review.googlesource.com/13560

Change-Id: Id72e5526c56e5e070b933d3b28dc503a5a2978dc
Reviewed-on: https://go-review.googlesource.com/13586Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>