Version 3 (modified by eamiri, 9 years ago) (diff)


Passes of the Compiler

  1. Parsing Python parser is used to parse the input. The output is an abstract syntax tree.
  1. Extracting List of Live Variables The list of live variables is extracted. The list will be used in dead code elimination.
  1. Inlining Functions calls are inlined. The functionality of this pass is restricted for now. This pass has a couple of internal phases in particular it handles all import statements.
  1. Translation The abstract syntax tree is translated to an abstract syntax tree based on bitExpr classes.
  1. Sym-Table Construction Symbol table is constructed.
  1. Conversion to SSA The code is converted to SSA. The SSA form used in the compiler is tailored to needs of the compiler.
  1. Creating Basic Blocks Based on occurrences of optimize pragma, new conditional statements are introduced which results in creation of new basic blocks of code.
  1. Applying Pragmas All optimize pragmas are applied, this means that in proper places of the code, occurrences of optimized variables are replaced by the constant value indicated by optimize pragma. No further simplification is performed.
  1. Normalize Converts code to three address code. This also involves common subexpression elimination.
  1. Code Simplification The code is simplified using boolean algebra rules, copy propagation and constant propagation. Constant propagation has two forms, backward propagation and forward propagation. The main source of simplifications is optimize pragma.
  1. Dead Code Elimination Given the list of live variables extracted in Pass 2, we go backwards in the code, and find all variables that live variables depend on. All other variables are dead and the lines that define them can be removed.
  1. Factor Out In order to reduce the size of code, the common code at the end of two branches of if-then-else statements, is removed from the branches and put right after that statement.
  1. While Loop Processing Extra operations for handling carry variables inside a while loop is inserted.
  1. Variable Information The code is analyzed to collect information about variable names and their type.
  1. Output The abstract syntax tree is translated to the equivalent C code.