Javascript:SpiderMonkey:OdinMonkey

Active

• Fix lazy-parsing/decompression memory-spike and performance hit for huge js files (bug 938385).
• Look at temporary garbage objects (viz., subviews) created in Emscripten DOM glue code, see if some basic escape analysis could avoid creating them at all.
• Standardize then implement SIMD extensions to JS (bug 894105) and then incorporate into asm.js
• Land experimental SharedArrayBuffer (pref'd off, bug 933001) and use this to add experimental pthreads support to Emscripten and evaluate on threaded codebases in preparation for a standards proposal.

Planned next projects

• Record enough information at compile time so that asm.js functions show up in:
  • the builtin FF profiler (bug 947996)
  • Error.stack
• Add && and || to asm.js to avoid sub-optimal control flow (bug 919052).
• Add missing math constants (bug 878488)
• Remove num-locals (bug 916612) and num-lines (bug 916564) parser limits.
• Mitigate 32-bit OOM problems: (bug 865959)
• ArrayBuffer.prototype.resize (bug 927182): to allow growable heap

Possible further optimization projects

• Compress asm.js cache entries
• Further improve load-time:
  • Start general JS parsing before the entire JS script has completed downloading so that asm.js compilation can overlap
  • asm.js parser: Avoid building an intermediate parse tree; type check during recursive descent bug 854061
• Improve heap access performance : bug 865516, bug 865523, bug 869606, bug 870743, bug 897425
• Further improve FFI calls : bug 882399, bug 886411, also stop spilling non-volatile registers
• Improve x86/ARM asm.js-to-asm.js ABI : bug 861785
• Extend the asm.js signal handler tricks to:
  • Remove stack overflow checks
  • Remove idiv branching
  • Remove double-to-int conversion branching (see also bug 818750)

Possible asm.js extensions that don't extend JS

• Effectively support 'goto' (even computed 'goto') by formalizing a pattern of while+switch that gets compiled as if it was goto
• Extend asm.js to better support dynamically linking asm.js modules (a mutable, callable array argument to asm.js module, like the PLT)
• Add enough try/catch to asm.js to allow compilation of C++ exceptions using the zero-cost implementation strategy
• Add DataView to avoid the alignment mask on asm.js heap accesses (this is mostly a problem of DataView being slow in all browsers)

Proposed future JS features that would be useful to asm.js

• ArrayBuffer.prototype.discard (bug 855669): to allow madvise(DONTNEED)
• FunctionPromise: bug 854627
• Typed Objects: (Typed Objects)
  • This feature comes with float32/uint64/int64 value types, which would be useful as scalar types in asm.js.
  • Formalize Typed Object "class declarations" in asm.js which could make asm.js a target for JVM/CLR/TypeScript (and allow these languages to reuse the builtin JS GC)

Current asm.js spec bugs

https://github.com/dherman/asm.js/issues?state=open

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Credit to John Howard