| Commit message (Collapse) | Author | Age | Files | Lines |
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The main benefit here is comparing VMs, instead of just comparing
each VM to itself after opts. Comparing VMs is a little tricky since there
is room for nondeterminism with how results are printed and other
annoying things, which is why that didn't work well earlier.
With this PR I can run 10's of thousands of iterations without finding
any issues between v8 and the binaryen interpreter. That's after
fixing the various issues over the last few days as found by this:
#2760 #2757 #2750 #2752
Aside from that main benefit I ended up adding more improvements
to make it practical to do all that testing:
Randomize global fuzz settings like whether we allow NaNs and
out-of-bounds memory accesses. (This was necessary here since
we have to disable cross-VM comparisons if NaNs are enabled.)
Better logging of statistics like how many times each handler
was run.
Remove redundant FuzzExecImmediately handler (looks like
after past refactorings it was no longer adding any value).
Deterministic testcase handling: if you run e.g. fuzz_opt.py 42 it
will run one testcase and exactly the same one. If you run without
an argument it will run forever until it fails, and if it fails, it prints out
that ID so that you can easily reproduce it (I guess, on the same
binaryen + same python, not sure how python's deterministic
RNG changes between versions and builds).
Upgrade to Python 3.
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* make DE_NAN avoid creating nan literals in the first place
* add a reducer option `--denan` to not introduce nans in destructive reduction
* add a `Literal::isNaN()` method
* also remove the default exception logging from the fuzzer js glue, which is a source of non-useful VM differences (like nan nondeterminism)
* added an option `--no-fuzz-nans` to make it easy to avoid nans when fuzzing (without hacking the source and recompiling).
Background: trying to get fuzzing on jsc working despite this open issue: https://bugs.webkit.org/show_bug.cgi?id=175691
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The main fuzz_opt.py script compares JS VMs, and separately runs binaryen's fuzz-exec that compares the binaryen interpreter to itself (before and after opts). This PR lets us directly compare binaryen's interpreter output to JS VMs. This found a bunch of minor things we can do better on both sides, giving more fuzz coverage.
To enable this, a bunch of tiny fixes were needed:
* Add --fuzz-exec-before which is like --fuzz-exec but just runs the code before opts are run, instead of before and after.
* Normalize double printing (so JS and C++ print comparable things). This includes negative zero in JS, which we never printed properly til now.
* Various improvements to how we print fuzz-exec logging - remove unuseful things, and normalize the others across JS and C++.
* Properly legalize the wasm when --emit-js-wrapper (i.e., we will run the code from JS), and use that in the JS wrapper code.
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After we added logging to the fuzzer, we forgot to add to the JS glue code the necessary imports so it can be run there too.
Also adds legalization for the JS glue code imports and exports.
Also adds a missing validator check on imports having a function type (the fuzzing code was missing one).
Fixes #1842
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This adds a new method of fuzzing, "translate to fuzz" which means we consider the input to be a stream of data that we translate into a valid wasm module. It's sort of like a random seed for a process that creates a random wasm module. By using the input that way, we can explore the space of valid wasm modules quickly, and it makes afl-fuzz integration easy.
Also adds a "fuzz binary" option which is similar to "fuzz execution". It makes wasm-opt not only execute the code before and after opts, but also write to binary and read from it, helping to fuzz the binary format.
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