Simplify regexp test call when the regexp starts and ends with '.*'.

Simplify regexp test call when the regexp starts and ends with '.*'. 

Committed: http://code.google.com/p/v8/source/detail?r=4799

[Lasse Reichstein, 2010-06-04 11:30:33]

LGTM

http://codereview.chromium.org/2645002/diff/2001/3001
File src/regexp.js (right):

http://codereview.chromium.org/2645002/diff/2001/3001#newcode262
src/regexp.js:262: var regexp_val;
How often do you hit this? (And how often will you hit it if you cache negative
results in the global regexp cache)?

http://codereview.chromium.org/2645002/diff/2001/3001#newcode299
src/regexp.js:299: if (%_StringCharCodeAt(this.source,0) == 46 && // '.'
You may want to try moving this.source to a local variable. It is used a lot.
Ditto for this.source.length.

http://codereview.chromium.org/2645002/diff/2001/3001#newcode313
src/regexp.js:313: if (!regexp_val.test(s)) return false;
You can cache the negative result in the regexp cache here (using the original
regexp as key). That means that next time you call test, the global regexp cache
will match and you don't even get here.

[sandholm, 2010-06-04 11:57:23]

http://codereview.chromium.org/2645002/diff/2001/3001
File src/regexp.js (right):

http://codereview.chromium.org/2645002/diff/2001/3001#newcode262
src/regexp.js:262: var regexp_val;
On 2010/06/04 11:30:33, Lasse Reichstein wrote:
> How often do you hit this? (And how often will you hit it if you cache
negative
> results in the global regexp cache)?
Caching negative results in the global regexp cache won't change the hit rate
for this cache as test is often called with a new string.

http://codereview.chromium.org/2645002/diff/2001/3001#newcode299
src/regexp.js:299: if (%_StringCharCodeAt(this.source,0) == 46 && // '.'
On 2010/06/04 11:30:33, Lasse Reichstein wrote:
> You may want to try moving this.source to a local variable. It is used a lot.
> Ditto for this.source.length.
Tried this. Causes regressions on some benchmarks

http://codereview.chromium.org/2645002/diff/2001/3001#newcode313
src/regexp.js:313: if (!regexp_val.test(s)) return false;
On 2010/06/04 11:30:33, Lasse Reichstein wrote:
> You can cache the negative result in the regexp cache here (using the original
> regexp as key). That means that next time you call test, the global regexp
cache
> will match and you don't even get here.
Often test is called with a new string so that won't really pay off in the end.