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  • Tamar Christina's avatar
    Refactored SymbolInfo to lower memory usage in RTS · 37473722
    Tamar Christina authored and Ben Gamari's avatar Ben Gamari committed
    Previously as part of #11223 a new struct `SymbolInfo` was introduced to
    keep track it the weak symbol status of a symbol.
    
    This structure also kept a copy of the calculated address of the symbol
    which turns out was useful in ignoring non-weak zero-valued symbols.
    
    The information was kept in an array so it means for every symbol two
    extra bytes were kept even though the vast majority of symbols are
    non-weak and non-zero valued.
    
    This changes the array into a sparse map keeping this information only
    for the symbols that are weak or zero-valued. This allows for a
    reduction in the amount of information needed to be kept while giving up
    a small (negligable) hit in performance as this information now has to
    be looked up in hashmaps.
    
    Test Plan: ./validate on all platforms that use the runtime linker.
    
    For unix platforms please ensure `DYNAMIC_GHC_PROGRAMS=NO` is added to
    your validate file.
    
    Reviewers: simonmar, austin, erikd, bgamari
    
    Reviewed By: simonmar, bgamari
    
    Subscribers: thomie, #ghc_windows_task_force
    
    Differential Revision: https://phabricator.haskell.org/D2184
    
    GHC Trac Issues: #11816
    37473722