This reverts CL 194297.

Reason for revert: introduced register allocation failures on PPC64LE builders.

Updates #33826
Updates #32781
Updates #34468

Change-Id: I7d0b55df8cdf8e7d2277f1814299b083c2692e48
Reviewed-on: https://go-review.googlesource.com/c/go/+/196957
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Martin Möhrmann <moehrmann@google.com>