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>