Add deopt fuzzer tool.

Add deopt fuzzer tool.

Can be run as a stand-alone script like run-tests. 

Executes first all tests of a given test suite to collect the maximum number of possible deopt points. Runs then a fuzzing phase with artificial deoptimizations triggered during testing.

Works for now with mjsunit and ia32 only.

R=jkummerow@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=15855

[Michael Achenbach, 2013-07-23 11:26:14]

PTAL

[Jakob Kummerow, 2013-07-23 15:13:43]

LGTM with comments.

Seeing how similar run-tests.py and run-deopt-fuzzer.py are turning out to be,
we should probably think about unifying the two at some point (either have a
single script, or factor out more of the shared implementation). But for now
let's keep them separate until deopt fuzzing works fully and the implementation
has stabilized.

(Later we can also add features that are missing for now, such as networked
execution.)

https://codereview.chromium.org/19931005/diff/1/tools/run-deopt-fuzzer.py
File tools/run-deopt-fuzzer.py (right):

https://codereview.chromium.org/19931005/diff/1/tools/run-deopt-fuzzer.py#new...
tools/run-deopt-fuzzer.py:246: options.distribution_factor1 = 0.0
might want to print a warning here too: "Invalid --distribution-factor1,
defaulting to 0". Same below.

https://codereview.chromium.org/19931005/diff/1/tools/run-deopt-fuzzer.py#new...
tools/run-deopt-fuzzer.py:320: return int(math.pow(float(m), (float(m) * c + l)
/ (float(m) + l)))
I think you can s/float(m)/m/ three times here.

https://codereview.chromium.org/19931005/diff/1/tools/run-deopt-fuzzer.py#new...
tools/run-deopt-fuzzer.py:378: analysis_flags = [
couple nits here:
(1) use proper string formatting
(2) be consistent about use of single vs. double quotes
(3) put related things onto the same line

    analysis_flags = ["--deopt-every-n-times", "%d" % MAX_DEOPT, 
                      "--print-deopt-stress"]

https://codereview.chromium.org/19931005/diff/1/tools/run-deopt-fuzzer.py#new...
tools/run-deopt-fuzzer.py:412: if line.startswith('=== Stress deopt counter: '):
nit: ""

https://codereview.chromium.org/19931005/diff/1/tools/run-deopt-fuzzer.py#new...
tools/run-deopt-fuzzer.py:416: print "Missing results for " + t.path
print "... %s" % t.path

https://codereview.chromium.org/19931005/diff/1/tools/run-deopt-fuzzer.py#new...
tools/run-deopt-fuzzer.py:419: with file(dump_results_file + "." +
str(time.time()), 'w') as f:
file("%s.%d.txt" % (dump_results_file, time.time()), "w")

https://codereview.chromium.org/19931005/diff/1/tools/run-deopt-fuzzer.py#new...
tools/run-deopt-fuzzer.py:433: print t.path + " " + str(distribution)
print "%s %s" % (t.path, distribution)

https://codereview.chromium.org/19931005/diff/1/tools/run-deopt-fuzzer.py#new...
tools/run-deopt-fuzzer.py:435: fuzzing_flags = ['--deopt-every-n-times', str(i)]
nit: "" (and ideally: "%d" % i)

[Michael Achenbach, 2013-07-24 12:04:37]

Committed patchset #2 manually as r15855 (presubmit successful).