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  1. 03 Apr, 2012 1 commit
  3. 02 Apr, 2012 1 commit
    • erikcorry's avatar
      Regexp: Improve the speed that we scan for an initial point where a non-anchored · f14b93a5
      erikcorry authored 
      regexp can match by using a Boyer-Moore-like table.  This is done by identifying
non-greedy non-capturing loops in the nodes that eat any character one at a time.
For example in the middle of the regexp /foo[\s\S]*?bar/ we find such a loop.
There is also such a loop implicitly inserted at the start of any non-anchored
regexp.

When we have found such a loop we look ahead in the nodes to find the set of
characters that can come at given distances.  For example for the regexp
/.?foo/ we know that there are at least 3 characters ahead of us, and the sets
of characters that can occur are [any, [f, o], [o]].  We find a range in the
lookahead info where the set of characters is reasonably constrained.  In our
example this is from index 1 to 2 (0 is not constrained).  We can now look 3
characters ahead and if we don't find one of [f, o] (the union of [f, o] and
[o]) then we can skip forwards by the range size (in this case 2).

For Unicode input strings we do the same, but modulo 128.

We also look at the first string fed to the regexp and use that to get a hint
of the character frequencies in the inputs.  This affects the assessment of
whether the set of characters is 'reasonably constrained'.

We still have the old lookahead mechanism, which uses a wide load of multiple
characters followed by a mask and compare to determine whether a match is
possible at this point.
Review URL: http://codereview.chromium.org/9965010

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11204 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
      f14b93a5
  5. 30 Mar, 2012 1 commit
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    • ricow@chromium.org's avatar
      Introduce code flushing of RegExp code. · 0f682143
      ricow@chromium.org authored 
      Due to issues relating mostly to chrome extensions we have lately been
running into OOMs that are caused by our executable space running
out. This change introduces flushing of code from regexps if we have
not used the code for 5 mark sweeps.

The approach is different from the normal function code flusing. Here
we make a copy of the code inside the data array, and exchange the
original code with a smi determined by the sweep_generation (a new
heap variable increased everytime we do mark sweep/compact). If we
encounter a smi in EnsureCompiled we simply reinstate the code
object. If, in the marking phase of mark sweep, we find a regexp that
already have a smi in the code field, and this is more than 5
generations old we flush the code from the saved index.
Review URL: http://codereview.chromium.org/7282026

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8532 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
      0f682143
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