code review 156108: add a match arena to regexp to avoid generating garbage.

add a match arena to regexp to avoid generating garbage.
simple regexps run 20x faster.
the regex-dna benchmark goes 3x faster.

[r, 2009-11-20 06:10:45]

Hello rsc (cc: golang-dev@googlegroups.com),

I'd like you to review the following change.

[rsc, 2009-11-20 06:29:58]

LGTM

http://codereview.appspot.com/156108/diff/1001/1002
File src/pkg/regexp/all_test.go (right):

http://codereview.appspot.com/156108/diff/1001/1002#newcode64
src/pkg/regexp/all_test.go:64: /*
uncomment

http://codereview.appspot.com/156108/diff/1001/1003
File src/pkg/regexp/regexp.go (right):

http://codereview.appspot.com/156108/diff/1001/1003#newcode767
src/pkg/regexp/regexp.go:767: // TODO: If the state were a vector and we could
do insert, have inputs always
You will still need the loop to check for a state
with the same index, but I think that with the
current addState code, s[i].match.m[0] <= begin
is always true in the test below.

[r, 2009-11-20 07:12:02]

*** Submitted as http://code.google.com/p/go/source/detail?r=b42108ef8a0b ***

add a match arena to regexp to avoid generating garbage.
simple regexps run 20x faster.
the regex-dna benchmark goes 3x faster.

R=rsc
CC=golang-dev
http://codereview.appspot.com/156108