Hi Antonio, On Mon, Mar 20, 2006 at 10:52:42AM +0100, Antonio Cuni wrote: > The first decision I took is whether to generate IL code (to be > assembled with ilasm) or C# code: I choose the first mainly because C# > lacks the goto statement and it would be difficult to implement flow > control.
This makes sense, I suppose even for more reasons than just the absence of goto's. There are other target languages that also lack goto's, so we might need some general way to "reverse-engineer" some structure from the graphs, in the same way that you consider a general way to turn the low-level operations into a more stack-machine-friendly representation. > As you can see there are many unnecessary operations: the result of > 'add' is stored to v12, loaded from v12, stored in v6 and then loaded > from v6! The same is true for the branch instruction, which is unneeded. I wonder how important this is at the moment. Maybe the .NET JIT compiler is good enough to remove all this. How does the resulting machine code look like? > I think it should be fairly simple to translate from the SSA form to a > more "stack-friendly" form useful for stack-based machines; the question > is: where to put such code? > Since it could be useful even for other backends, it would be nice to > put it in some place where it can be shared from several backends: one > option could be to write it as a backend optimization, but in this case > we have to introduce new low level operations for stack manipulation, > such as 'push', 'pop' or 'dup'. Also useful for other back-ends would be a way to reconstruct some kind of "expression tree". For example, in Squeak, it is more efficient to generate a single complex expression instead of a lot of simple expressions, because of the shuffling of the local variables that the latter requires. The link with your suggestion is that these complex expressions are also very stack-machine-friendly. It would probably make sense to write this as a function that takes a single block and produces a list of "complex expression" objects -- to be defined in a custom way, instead of trying to push this into the existing flow graph model. A bientot, Armin _______________________________________________ pypy-dev@codespeak.net http://codespeak.net/mailman/listinfo/pypy-dev
