lexopts.txt

来自「开放源码的编译器open watcom 1.6.0版的源代码」· 文本 代码 · 共 85 行

Optimizations Driven by Lexus
-----------------------------

(1) Templates
-------------

    - commands, for a template instantiation, exist to:
        (a) prohibit generation of template definitions
        (b) force generation of template definitions
        
    - both ANSI and Microsoft forms of commands
    
    - implement them
    
    - benefits:
    
        (a) required instantiations are generated only once
        
        
(2) Generated Class Functions
-----------------------------

    - generated in the module containing
    
        (a) a non-inlined destructor
        
        (b) if not (a), in all modules containing something out of line
            - out of line function
            - static data
            
        (c) if not (a) or (b), in each module
        
    - (a) or (b) generate all functions
        - when doing this, we want to disable protection errors
        - would we get protection errors in other cases
        - we will likely need some global mode to:
            - disable diagnostics when doing default generation
            - enable diagnostics but not generate code when not doing
              default generation

    
    - (c) generates on demand
    
    - what is "all functions" ?

        - default constructor
        - default destructor
        - default copy constructor
        - default assignment operator
        - virtual-function tables
        - virtual-base tables
        - inline functions referenced by the class type signature

        plus (we have to decide)

        - addressiblity thunks
        - type signature
        - default-argument inlines
        - inlined functions that are static'ed by overflowing inline_depth 
        - inlined functions in a class
        
    - proposed changes to CLASS_INFO: add 3 flags
        
        - checked_home_module: set when class has been examined (after eof)
            to see if we are compiling a home module for this class
            
        - home_module: valid only if "checked_home_module" is set
            - indicates cases (a) or (b) when set
            
        - default_gen: valid only if "checked_home_module" is set
            - indicates that class declaration indicates no home module can
              exist
              
    - what are we not optimizing:
    
        (a) classes with everything inline: optimization can be triggered by
            adding a static char variable and creating a new source module
            containing only the definition of that variable.
            
        (b) we are marginally sub-optimal (for most users) when a class has
            no non-inlined destructor, has multiple source files, and has
            non-inlined components
            - look at our classes to see if this is the case
                - string, complex, iostream, containers, STL