cmd/compile/internal/inline: debug flag to alter score adjustments
Add a debugging flag "-d=inlscoreadj" intended to support running
experiments in which the inliner uses different score adjustment
values for specific heuristics. The flag argument is a series of
clauses separated by the "/" char where each clause takes the form
"adjK:valK". For example, in this build
go build -gcflags=-d=inlscoreadj=inLoopAdj:10/returnFeedsConstToIfAdj:-99
the "in loop" score adjustments would be reset to a value of 15 (effectively
penalizing calls in loops) adn the "return feeds constant to foldable if/switch"
score adjustment would be boosted from -15 to -99.
Change-Id: Ibd1ee334684af5992466556a69baa6dfefb246b3
Reviewed-on: https://go-review.googlesource.com/c/go/+/532116 Reviewed-by: Matthew Dempsky <mdempsky@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>