internal/profile: use internal/lazyregexp for the legacy parser

Per benchinit, this makes a big difference to init times:

	name             old time/op    new time/op    delta
	InternalProfile     185µs ± 1%       6µs ± 1%  -96.51%  (p=0.008 n=5+5)

	name             old alloc/op   new alloc/op   delta
	InternalProfile     101kB ± 0%       4kB ± 0%  -95.72%  (p=0.008 n=5+5)

	name             old allocs/op  new allocs/op  delta
	InternalProfile       758 ± 0%        25 ± 0%  -96.70%  (p=0.008 n=5+5)

The fixed 0.2ms init cost is saved for any importer of net/http/pprof,
but also for cmd/compile, as it supports PGO now.
A Go program parsing profiles might not even need to compile these
regular expressions at all, if it doesn't encounter any legacy files.
I suspect this will be the case with most invocations of cmd/compile.

Updates #26775.

Change-Id: I8374dc64459f0b6bb09bbdf9d0b6c55d7ae1646e
Reviewed-on: https://go-review.googlesource.com/c/go/+/460545
Reviewed-by: Michael Pratt <mpratt@google.com>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

0 files changed, 0 insertions, 0 deletions