imcc v0.0.1

imcc is the intermediate compiler for Parrot.

Why? Writing a compiler is a large undertaking. I'm trying
to take some of the load off of potential language designers,
including the Perl6 compiler itself. We can provide a
common back-end for Parrot that does:

   Register Allocation and Spillage
   Constant folding and expression evaluation
   Instruction selection.
   Coalescing, instruction scheduling, etc.
   
This way, language designers can get right to work on

   Tokenizing, parsing, type checking AST/DAG production

Then they can simply spit out IR to imcc which will compile
directly to Parrot bytecode, potentially skipping the
assembler altogether.

So far, all the compiler does (besides translating the IR to pasm) is
register allocation. I like Steve Muchnick's MIR language, and I'm
taking a few things from it.

Presently you can write code with unlimited symbolics or named
locals and imcc will translate to pasm.

I expect the IR compiler to focus on staying FAST, simple and
maintainable, and never develop featuritis, however I want it to be
adequate for all languages targetting parrot. Did I mention that
it needs to be FAST?

We have other options like having imcc to become an assembler in its
own right, which is fine by me, but for now, I think Parrot is changing way
too fast to have another assembler branch).


Register Allocation

  The allocator uses graph-coloring and du-chains to allocate registers
  for lexicals and symbolic temporaries.

Spilling

  Currently spillage is not implemented.

Optimization

  At this level, many optimizations are simple, like register
  coalescing, redudant copies, and constant expression evaluation.
  This will wait until the compiler is fully featured and well
  designed and works well enough as the backend compiler for languages
  targetting Parrot.


Why C and Bison?

  Until Perl6 compiles itself and is fast, a Bison parser is
the easiest to maintain. An additional, important benefit, is
C-based LALR parser are pretty darn fast. Currently assembling
Parrot assembly on the fly is just too slow with assemble.pl,
although new things are in the works.


Please mail perl6-internals@perl.org with bug-reports or patches.

Maintainer and Author:   Melvin Smith (melvin.smith@mindspring.com)