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Semantic Check Error __builtin_prefetch

Error Information

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 error: argument to '__builtin_prefetch' must be a constant integer 
    __builtin_prefetch(address, forWrite); 
    ^

Problem

In the code, the second parameter of __builtin_prefetch must be a constant. Therefore, the __builtin_constant_p should be called to check whether the second parameter forWrite from the code example is a constant. However, this causes a semantic check error in Clang.

Code Example

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static void prefetchAddress(const void *address, bool forWrite) { 
    if (__builtin_constant_p(forWrite)) { 
        __builtin_prefetch(address, forWrite); 
    } 
}

Solution

Convert the function to a macro function as follows:

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##define prefetchAddress(address,forWrite) do{\ 
  if (__builtin_constant_p(forWrite)) {      \ 
    __builtin_prefetch(address, forWrite);   \ 
  }                                          \ 
}while(0)