Wednesday, July 31, 2013

Status Updates - Part 3

As I was on vacations, I did make smaller tasks in the free time, but there are some note-worthy updates, mostly in optimization front:
- there is a [PureMethod] attribute that you can mark functions. If this attribute is found, the function is considered pure, and as a consequence, if you call it with constants, at compile time, the code is evaluated. It will be great if in future the functions are computed for purity, but this is a longer plan (is possible to be done, but are many cases)
- there is an inlining code possible (at least for simple functions), but the optimization is disabled as it requires a lot of testing. Anyway, this opens a lot of possibilities on matter of performance: if you have a call of a function with a constant, and this method is inlined, more optimizations can successfully occur. In the medium plan is to bug-fix it and test the inliner to work with most small cases
- the compiler optimizer is split into parallel and serial optimizations. The good part of it, is that as more functions are initially defined, all cores are used to compile every function into cores. The inliner (or future purity computer) are serial optimizations. This reduces the compilation time of NBody (on my I5 first gen) from 200 ms to 150 ms of generating the C++ code, still the C++ code compilation takes longest
- the function bodies are defined like a sequence of simple operations. So, optimizations that do delete one item, are rewritten to be way faster by doing the deletes in batches
- unit tests are a bit weaker right now, but they do compile/run much faster. They test the capability of the compiler to give an output, not the execution output. They run now properly, so the unit testing is working again

So in short, you will get the same code (if you don't mark it with [PureMethod] everywhere) faster.

Added code to reflect APIs, it will be needed to generate stubs for OpenRuntime code. This code needs some love, and if there are any readers interested, would it be great if someone can look into generating some library empty wrappers.

Future plans:
- enums support
- string type improvements (it depends on enum in part)
- string merging - all occurrences of the same string should be defined just once in a string table
- (maybe) fixes into inliner - at least the inline of functions call overhead should not exist at least in some cases that can be detected: empty functions, simple setters/getters
- (maybe) a purity checker - computing purity gives speedups extensively if the developer uses constants. So if the functions can be computed for their purity (without [PureMethod] annotations), when called everywhere with constants, they will give zero overhead on execution time

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