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  1. Mar 12, 2009
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  6. Mar 07, 2009
    • Duncan Sands's avatar
      Introduce new linkage types linkonce_odr, weak_odr, common_odr · 12da8ce3
      Duncan Sands authored
      and extern_weak_odr.  These are the same as the non-odr versions,
      except that they indicate that the global will only be overridden
      by an *equivalent* global.  In C, a function with weak linkage can
      be overridden by a function which behaves completely differently.
      This means that IP passes have to skip weak functions, since any
      deductions made from the function definition might be wrong, since
      the definition could be replaced by something completely different
      at link time.   This is not allowed in C++, thanks to the ODR
      (One-Definition-Rule): if a function is replaced by another at
      link-time, then the new function must be the same as the original
      function.  If a language knows that a function or other global can
      only be overridden by an equivalent global, it can give it the
      weak_odr linkage type, and the optimizers will understand that it
      is alright to make deductions based on the function body.  The
      code generators on the other hand map weak and weak_odr linkage
      to the same thing.
      
      llvm-svn: 66339
      12da8ce3
    • Dan Gohman's avatar
      Arithmetic instructions don't set EFLAGS bits OF and CF bits · ff659b5b
      Dan Gohman authored
      the same say the "test" instruction does in overflow cases,
      so eliminating the test is only safe when those bits aren't
      needed, as is the case for COND_E and COND_NE, or if it
      can be proven that no overflow will occur. For now, just
      restrict the optimization to COND_E and COND_NE and don't
      do any overflow analysis.
      
      llvm-svn: 66318
      ff659b5b
  7. Mar 05, 2009
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