$Id: TODO-PETIT 2917 2006-04-27 21:25:06Z tov $

TODO / IN PROGRESS
28 July 2003 / lth

Petit Larceny on Sparc/Solaris and other big-endian Unix:
 - have defined Util/unix-be.sch and Util/nbuild-param-C-be-unix.sch
 - can load compiler
 - can compile heap image
 - can compile and link RTS
 - RTS loads and runs in heap image
 - above process is portable (enough)
 - can rebuild itself in the interpreter
 - Must fix: Rts/Makefile is a mess because it has too many things 
   in it that need configuring by hand; it is not nearly portable.  
   Much can be done by requiring some non-basic Make system 
   (GNU Make, say) but then Win32 may suffer?  Am working on using
   Larceny for this, see Rts/makefile.sch.
 - Must do: build and test twobit
 - Must do: can we fix dynamic loading of compiled twobit?

Petit Larceny on x86 Linux:
 - Must test this (little endian)

Compatibility packages:
  Must add call-with-binary-input-file and call-with-binary-output-file
  to the compatibility packages?  These are now used by the twobit
  drivers and the heap dumper.  (Do we even care about building under
  other systems any more?)

  Must clean up dumpheap-unix.sch so that it is usable; the rest of the
  system may have diverged (again).  (Works OK on MacOS X and Solaris!)

Primitives:
  - Some primitives (in the 500 series) must be implemented

Peephole optimization:
  - Optimizations have been implemented, not enabled by default
  - Must test the peephole optimizations.  Almost all have been tested already,
    see testpeep.sch in this directory.
  - Must recompile everything with peephole optimization enabled
  - Some test cases it should get right but does not:
       (lambda (v) (vector-ref v 10))
       (lambda (v n) (vector-ref v n))
    In the first case it does not generate code that the peephole optimizer
    is able to match on (because the peephole optimizer does not match well
    on constant indices, because the optimizer removes half of the pattern).
    In the second case the optimizer matches but there are still five
    instructions generated, and a lot of access to the register file, which
    is not all that good, certainly not on RISC systems where all operands
    could be loaded once.
  - Another case it should get right:
        op2         <:fix:fix,3
        branchf     1005,5
    It's sort of stupid to optimize the comparison and then have to generate
    and test a boolean.

Loading compiled code:
  Dynamic loading of objects so that we can compile to FASL without
  having to rebuild the executable:

	> (compile-files '("fib.sch") "fib.fasl") ; in Util/win32.sch
	> (load "fib.fasl")                       ; loads the dll too!
	> (fib 10)
	55

  The basic architecture is to compile a *group* of files into FASL, but
  their code will be dumped into a single shared object.

  The code basically works -- the DLL can be loaded, the code can be run.

  To fix:
  - Must try to build the development environment as FASL.

    This sort of works now, except that:
     - The resulting .c file is 6MB and compilation with optimization
       enabled never completes (CodeWarrior)
     - Incremental recompilation is not possible because of the *one*
       .c file; there is nothing to be incremental about
     - Compiling without optimization works but linking to a dll fails
       on Win32 because the code is missing _memset and __stack_alloc; 
       the former is obvious but the latter may be some sort of MWC rts thing?

    A better solution is to generate separate .c and .obj files but then
    link them all into a dll.  This should not be a problem.

  - Compile-files must probably always recompile all files, not check
    if the obj or c file exists, as it does now
  - Debug info: I'm working on getting debug info into the dll (experimenting
    with -g to mwcc and mwld, have not tested.)

Other performance:
  - Inline allocation for CONS and peepholed MAKE-VECTOR, at least.
  - Consider further peephole optimizations
      
Cleanup:
  - *Maybe* move compile-files into standard driver code?
  - Compile-file should be an alias for compile-files with just one
    input file
  - Compile-files could default the output name to the first name
    in the input list


Bugs to fix:
  - One bug report about heap loader from Brown U?

Test cases to add to test suite:
  - Bignum bug: This would result in a division by zero error:
     (/ 0 4217293152016490)
  - Bignum bug: This used to return an illegal ratnum (both numerator
    and denominator were negative):
       (/ -123234566789000009 -1234512345000)
  - Bignum bug: This would return the wrong sign (should be positive):
      (remainder 3303030303030 -12345566789012)
  - Number bug: expt 0 anything returns 1, but should not, here are tests
    and desired results:
      (expt 0 0) => 1
      (expt 0 2) => 0
  - Petit arithmetic bug:
      (+ (sqrt -3.9) 2) => 2.0+1.9748417658131499i
    but would previously return 2.0 only
  - This signals a compiler error in some cases:
(compile 
  '(define (read-sharp-thingie port)
    ;; ASSERT: peek-char is #\#
    (consume-char port)
    (let ( (next (peek-char port)) )
      (case next
        (( #\t #\f #\T #\F ) (make-boolean port))
        (( #\e #\i #\o #\b #\d #\x #\E #\I #\O #\B #\D #\X )
         (read-number-loop '(#\#) port))
        (( #\\ ) (read-character port))
        (( #\( ) (read-vector    port))
        (( #\' ) (read-sharp-sym port))
        (else (error "Unknown sharp syntax" next)))
  ) )
)


PORTABILITY TODO

Apparently the MacOS X system header files define BIG_ENDIAN, so we
might use a different name for Larceny for this macro.


PERFORMANCE TODO

Can use first-class labels under Gnu C, this should be a big win.
