runtime: drop stack-allocated pcvalueCaches

Now that pcvalue keeps its cache on the M, we can drop all of the
stack-allocated pcvalueCaches and stop carefully passing them around
between lots of operations. This significantly simplifies a fair
amount of code and makes several structures smaller.

This series of changes has no statistically significant effect on any
runtime Stack benchmarks.

I also experimented with making the cache larger, now that the impact
is limited to the M struct, but wasn't able to measure any
improvements.

This is a re-roll of CL 515277

Change-Id: Ia27529302f81c1c92fb9c3a7474739eca80bfca1
Reviewed-on: https://go-review.googlesource.com/c/go/+/520064
Auto-Submit: Austin Clements <austin@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Austin Clements <austin@google.com>

0 files changed, 0 insertions, 0 deletions