This reverts CL 525035.

Reason for revert: breaks many Google-internal tests (#63739), suspected miscompilation

Change-Id: I8cbebca0a187d12e16c405b2373c754e4a397ef4
Reviewed-on: https://go-review.googlesource.com/c/go/+/537598


Reviewed-by: Bryan Mills <bcmills@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Auto-Submit: Bryan Mills <bcmills@google.com>