Monday, June 15, 2009

[LIR Compiler/Assembler?] Current Status

We hid a roadblock last week when it came to our notice that another version of LIR Assembler( was being developed by Graydon Hoare(graydon), using only handcoded c/c++. The whole of last week went into deciding what should be done with the two working versions, seemingly both equally developed upto a certain extent.
The major problem was in merging the two forks - we were using a parser generator based approach, and graydon was using handcoded c++. It is far from trivial to merge the two, and hence, one version had to go. We spent one day going over the pros and cons of either approach. The summary of our discussion follows -
Graydon was advocating the fact that parser generators lead to 'mucky' .y files, a tool dependency, and are difficult to land.
Our case was that the .y files lead to much cleaner, neater classified code, separating the logic from the implementation to a certain extent. It involved significantly lesser number of code lines, and would also be extensible/modifiable(easily) in the future if additional syntax requirements appear.
As things turned out, we were deadlocked, and the decision to choose one particular fork lay upon me.
I went with graydon's version.

graydon's version was actually going to be landed in the tracemonkey repo, and this was one of the reasons I chose his version. The remainder of the week was spent in making lirasm(as our new lir assembler is now called) appropriate for the source tree, and then landing it in the repository.
During this time, I read up on Mercurial Queues(MQ), and learnt about the Bugzilla way of doing things (using patches, filing bugs) compared to the BitBucket approach we used earlier.
Things will get on track from today probably, and we have a bug to work on(

The main setback of the whole duplication situation was time. When it occurred, things were going very - I mean very smoothly, and it really seemed most of the work for LIR Compiler would be finished in two weeks time. I will get more idea today on how much time this is going to take now.

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