David Mandelin’s blog

If you’re reading this, chances are that you already know about SquirrelFish, Appl/WebKit’s new Javascript implementation. Early tests show SquirrelFish to be 60% faster than WebKit 3.1 JS, 46% faster than Spidermonkey and 52% faster than TT (Tamarin Tracing) on SunSpider.
Clearly we have some work to do. The plan is to improve TT so that [...]

Whew. Reading all this TT code is fascinating, but also tiring, hard work. Anyway, I’ve hit almost all the high points by now, and I’ve traced out the JITting process all the way from ABC bytecode to native compiled traces. The questions I have left are about how traces actually get run, plus some related [...]

In part III, I went over how TT generates LIR traces. Now, I’m going to look into the trace optimization and machine code generation process. The code for this is mostly in the nanojit/ directory.
Keep in mind that a trace is always straight-line code in SSA form. This makes optimizations easier to implement, so it [...]

Program Form 3: LIR. I believe LIR stands for low-level intermediate representation (although I’ve also heard linear intermediate representation). Typically, in a compiler or VM LIR is the lowest-level (and last) form of machine-independent compiler representation, and looks much like a machine-independent assembly language. TT’s LIR plays the same role but has some special features [...]

The Need for Forth Subroutines. I had a really hard time tracking down how TT adds a pair numbers (ActionScript code like “sum += i”) worked until I finally figured out that ECMAScript “+” is not a primitive operation in TT. This makes perfect sense now, as “+” is complicated: it has to do different [...]

Tamarin (technically, tamarin-tracing, henceforth TT)-related projects keep peeking up at me from the horizon. First, there’s a good chance I’ll have an intern working on TT this summer. And then there’s this “Tracehydra” idea. It’s a way to connect Spidermonkey’s JS parser with the TT execution engine. This is the plan:

Where “profit” means “run Javascript [...]

Time for a hardcore static analysis post. By the way, if anyone reading this knows about theorem provers, I could really use your help: what’s a solid off-the-shelf prover that will solve my formulas (see below)?
I’m working on bug 420933, which is a request for a static checker for XPCOM outparam usage. In short, XPCOM [...]

MXR is cool. I use it all the time. But those of us that have been using or creating Dehydra know that Dehydra could be used to make MXR a lot cooler. I don’t seem to have time to work on it, though, so I thought I’d throw some ideas out here, to see if [...]

1. For my own comprehension, I used Dehydra GCC + Graphviz to print a class hierarchy diagram for the Mozilla string classes (i.e., everything defined in xpcom/string). The results are here.
I was a little surprised that nsSubstring_base is the root, because in nsTAString.h, the root is nsTAString_CharT. Turns out that is #defined to nsSubtring_base in [...]

I’ve been using DTrace on Leopard in my recent work, and while it’s a great tool, the C++ support is confusing and I couldn’t find proper documentation. But eventually I found sketchy documentation that gave me the answers, so in the interest of saving others from pain:
Basic Call Profiling. One of the most basic profiling [...]