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[JS-internals] Jit DevTools 0.0.1


Nicolas B. Pierron via lists.mozilla.org

Hello everybody,

I am please to do an early announce a new tool named Jit DevTools.

This new tool is an addon which mostly target Jit developers.  It uses the recently added Debugger.onIonCompilation hook to display the latest MIR [1] and LIR graphs within the dev tools.

To use this tool, go to a web page, and open the Jit DevTools panel, then wait until a function got compiled.

Once a function is compiled, you can select a compiled script, which will display the MIR graph of the compilation.  If you need to, you can also have a look at the LIR graph.  The output is similar to the one rendered with iongraph [5].

By selecting any inlined script, the background of the block titles will change color, if the block correspond to the inlined instance.  This feature is quite useful to identify how a function plays in a compiled script.

You might find this tool quite handy to use for the following use cases:
– Investigating DOM optimization.
– Investigating jsperf issues.
– Comparing function implementations, and impacts on the generated code.

This addon works on optimized builds, and even with parallel compilation enabled.

You can download [2] this early version from http://people.mozilla.org/~npierron/jit-dev-tools/ , or build it your-self by using the sources [3] with jpm tool [4].

Have fun, and enjoy.

[1] http://people.mozilla.org/~npierron/jit-dev-tools/jit-dev-tools-0.0.1.png
[2] http://people.mozilla.org/~npierron/jit-dev-tools/jit-dev-tools-0.0.1.xpi
[3] https://github.com/nbp/jit-dev-tools/
[4] https://developer.mozilla.org/en-US/Add-ons/SDK/Tools/jpm
[5] https://developer.mozilla.org/en-US/docs/Mozilla/Projects/SpiderMonkey/Hacking_Tips#Using_IonMonkey_spew_%28JS_shell%29

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