Hello Alan,
> I've just put up a short description of the current state of the
> research on the feasibility on PHP#, developing a .net CIL bytecode
> compiler for PHP. If anyone wants to add 'constructive comments' to it,
> please fire away..
>
> http://www.akbkhome.com/Projects/PHP_Sharp
This is an interesting effort, here are some bits that you might find
useful:
* Microsoft's JavaScript compiler is also a dynamically typed
language. You might want to look at the compiler output for
`jsc' to see which tricks they use to deal with dynamic types.
* Microsoft VB.NET compiler also does tricks like that, for
example if the compiler can infer the types of variables,
it will use the most efficient mechanism possible.
For example, `int + int' can be encoded directly using CIL
instructions:
load-integer a
load-integer b
add
but when the compiler can not decide what to
do, it has to call a support routine in the runtime:
load-thing a
load-thing b
call Add_two_unknown_objects
Or even:
load-integer a
load-thing b
call Add_Integer_And_Unknown
* The Microsoft JSC compiler is interesting, because its
implemented in C#, and is available as a runtime class
this allows `eval' to actually compile code freshly.
* Optimizing dynamic typed languages
It has been debated that the CIL is a language that is good for
statically typed languages, but a poor choice for dynamic
languages. I think that this is a gross miss-representation.
In fact every computer architecture works better with statically
typed languages than dynamic languages (ie, the x86 is not an
architecture for "hosting" dynamically typed languages), but
clever tricks can be used to host any language on them.
For example the Mono JIT inlines a few calls (Math.Sin,
Math.Cos) with direct FPU instructions.
I would be entirely possible to extend this mechanism in the
future to handle particular calls to supporting routines in the
runtime to inline the code directly (if we believe that they
make sense, or that they are a performance improvement).
So say your language needs to do an indirect call, and you use a
helper function for this:
load-args
ldobj TheObjectToCall
ld-int some-index.
call IntPtr
[MyPHPRuntime]Runtime.ExecuteMethodByLookingMethodUp(object,string)
call-by-pointer
And lets imagine that the routine above returns a pointer, and
that it could be inlined nicely by doing some kind of static
lookup, we could extend the JIT (or have a JIT plugin mechanism)
that would inline the above call into, say, an indirect call
with an offset without having to call the lookupmethod routine.
Miguel
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