Javascript:SpiderMonkey:OdinMonkey

Active

• Optimize constant-additions in masked heap accessed: bug 915157
• Standardize and 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 Math.min/max to asm.js standard math library (they have more optimal implementations than you can express with just ternary)
• Add missing math constants (bug 878488)
• Mitigate 32-bit OOM problems: (bug 865959)
• ArrayBuffer.prototype.resize (bug 927182): to allow growable heap
• Move code generation into the parallel compilation tasks (bug 959263)
• Remove async-script requirement for asm.js caching: (bug 961057)

Possible further optimization projects

• Further improve load-time:
  • Start general JS parsing before the entire JS script has completed downloading so that asm.js compilation can overlap (and we'd be justified in doing all script parsing off the main thread)
  • asm.js parser: Avoid building an intermediate parse tree; type check during recursive descent bug 854061
• Compress more than just the source in asm.js cache entries
• Further improve heap access performance : 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 require new JS features

• 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)
• 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)
• FunctionPromise: bug 854627
• Add "AsmFunction" constructor that threw informative exception on validation failure.: (bug 952847)

Current asm.js spec bugs

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

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Credit to John Howard