This reverts commit 041ecb69.

Reason for revert: Not working on S390x and some 386 archs.
I have a guess why the S390x is failing.  No clue on the 386 yet.
Revert until I can figure it out.

Change-Id: I64f1ce78fa6d1037ebe7ee2a8a8107cb4c1db70c
Reviewed-on: https://go-review.googlesource.com/38790Reviewed-by: Keith Randall <khr@golang.org>