README for lab4: FIR Generation
Ling Li & Xin Yu, Caltech, 02/26/2001
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We implemented the CPS, ESC, closure conversions and the dead code
elimination. All 4 tests ran perfectly.

The test?.ir and test?.out files were generated at stage 7.

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Changed files (from lab3):
   fc_ast/fc_ast_lex.mll      Lexing
   fc_ast/fc_ast_parse.mly    Parsing
   fc_ir/fc_ir_ast.ml         IR generation
   fc_fir/fc_ir_cont.ml       CPS conversion
   fc_fir/fc_ir_esc.ml        Escape analysis
   fc_fir/fc_ir_closure.ml    Closure conversion
   fc_fir/fc_fir_dead.ml      Dead code elimination

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Main ideas:
   1. CPS: Insert continuation to all non-local function definitions.
           We also need to convert types (such as type in LetBinop).
   2. ESC: Create frames to store local variables.
           Be sure to copy all arguments of a function to its frame,
           and convert framed variables to corresponding fields.
   3. Closure: Close all functions.
           Every global function takes data_seg and exit as args.
   4. Dead code elimination: Eliminate useless codes and types.
           Assignment to a non-free variable is useless.
           Functions never called from global functions are useless.
           Types never used (such as empty frames) are useless.

Functions added and Bugs fixed to Lexer/Parser
   1. The 3rd entry of DefFun should be return type, not the type of
      the whole function.
   2. Support more float constant such as 3e-4.
   3. Support string constant merging, such as
         char *s = "Hello " "World";
      will be interpreted as
         char *s = "Hello World";
   4. Skip ^M in DOS format file.

Functions added and Bugs fixed to IR generation
   1. UNotOp now is transformed into IfThenElse.
   2. squash_array_type added.
   3. uarith of general expressions (not only AtomVar) fixed.
   4. convert_args (used to be called convert_to_typelist) now uses
      SemException ArityMismatch instead of Invalid_argument when the
      two lists do not meet in length.

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To do:
   1. Old problems in Lab 2 and Lab 3.
   2. Other optimizations.
   3. Make external functions escapable.

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This README file together with the programs can be found at
http://www.cs.caltech.edu/~ling/course/cs134b/lab4/