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  • Rafael Espindola's avatar
    Sorry for such a large commit. The summary is that only MachO cares about the · 93e3cf0e
    Rafael Espindola authored
    actuall addresses in a .o file, so it is better to let the MachO writer compute
    it.
    
    This is good for two reasons. First, areas that shouldn't care about
    addresses now don't have access to it. Second, the layout of each section
    is independent. I should use this in a subsequent commit to speed it up.
    
    Most of the patch is just removing the section address computation. The two
    interesting parts are the change on how we handle padding in the end
    of sections and how MachO can get the address of a-b when a and b are in
    different sections.
    
    Since now the expression evaluation normally doesn't know the section address,
    it will think that a-b needs relocation and let the MachO writer know. Once
    it has computed the section addresses, it calls back the expression evaluation
    with the section addresses to resolve these expressions.
    
    The remaining problem is the handling of padding. Currently it will create
    a special alignment fragment at the end. Since that fragment doesn't update
    the alignment of the section, it needs the real address to be computed.
    
    Since now the layout will not compute a-b with a and b in different sections,
    the only effect that the special alignment fragment has is update the
    address size of the section. This can also be done by the MachO writer.
    
    llvm-svn: 121076
    93e3cf0e
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