JavaScript Implementations
JavaScript Implementations
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talk-jsengines-cphjs-2012
Presentation at CopenhagenJS about JavaScript implementationsOn Github rasmuserik / talk-jsengines-cphjs-2012
JavaScript Implementations
12.12.12CopenhagenJS talk by Rasmus Erik
The Talk
- How: interactive - interrupt, ask questions
- Why: brush up on state of JavaScript engines
Rasmus Erik
- CS / programming language geek, LightScript
- Work includes bugfixes in Rhino and SpiderMonkey
Outline
Major open source implementations
(SpiderMonkey, JavaScriptCore, v8, Nashorn/Rhino)Selected engine features
(inline cache, hidden classes, values, gc)SpiderMonkey
- JavaScript engine for Firefox
- Used in Adobe Acrobat, CouchDB, MongoDB, Riak, ...
- Trace-, Jäger-, and IonMonkey
JavaScriptCore
- JavaScript engine for Safari
- Used in Qt 4.7+, ...
- Low-level interpreter, Baseline JIT, DFG JIT
v8
- JavaScript engine for Chrome
- Used in node.js, CouchBase, ...
- Full compiler, optimising compiler
Nashorn/Rhino
- JavaScript engine for Java
- Used in Java-scripting, node.js-api in progress.
- Piggybacking on JVM (jit, gc, ...)
Outline
Major open source implementations
(SpiderMonkey, JavaScriptCore, v8, Nashorn/Rhino)Selected engine features
(inline cache, hidden classes, values, gc)Inline cache
- Cache type information at execution point
- v8 fast monomorphic, SpiderMonkey PICs, LLIN external, invoke dynamic
- Fast when same type at code
Hidden classes and types
- Add property to object → change class
- Fast property access
- Initialise objects in same order
Values and unboxing
- SMI (small int), v8
- NaN-boxing, JSC and SpiderMonkey
- Java objects, Rhino/Nashorn
Generational Garbage Collection
- Young generation: copying GC. Older: mark'n'compact
- In v8 and JVM, not in JSC(on its way) or SpiderMonkey
- Fast for short lived objects