V4

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Revision as of 16:26, 11 January 2016 by Mathias Hasselmann (talk | contribs)
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V4 Javascript Engine

Why it was created?

Environment Variables

You need to set specific environment variables to debug this engine. In this wiki only few of them are described. To get full list of them you can try to open qtdeclarative.pro and search for text "QV4_.

  • QV4_SHOW_IR - prints intermediate representation of code. It's rather long output because many optimisation techniques are applied.
  • QV4_SHOW_ASM prints dissassembly output. If it prints message disassembly not available for range additional macros will have to be added which currently requires significant effort; so start your hacking from qtdeclarative/src/3rdparty/masm/disassembler/Disassembler.cpp
  • QV4_FORCE_INTERPRETER - disables just-in-time compilation. This usually significantly degrades performance and therefore only should be used for debugging purposes.

Hacking

TODO: maybe explain main purprose of some subprojects (where parsing, where optimisations, where jitter is executed..)

Running the EcmaScript 262 Test suite

It's reasonable to verify new features by running the EcmaScript 262 test suite.

  1. Check out the test suite submodule repository:
 git submodule update --init --checkout tests/manual/v4/test262
  1. Run the wrapper script in the tests/manual/v4 sub-directory:
   python ./test262.py