[cfe-dev] "You don't pay for what you don't use" principle violation?

[Fernando Pelliccioni]

Hi all,

Is there any reason why the following code produces the attached assembly
code?

    struct X { int v; };

    int func( X** x, int n )
    {
        int sum = 0;

        while ( n > 0 )
        {
            sum += (*x)->v;
            ++x;
            --n;
        }
        return sum;
    }

    int main() {}

The "func" function is not used, I think it should be omitted by the
compiler.

If I change the function to a template function

    template <typename T>
    int func( T** x, int n )
    {
        int sum = 0;

        while ( n > 0 )
        {
            sum += (*x)->v;
            ++x;
            --n;
        }
        return sum;
    }

Then, no code is generated.


Compiled using:
    clang++ -S -O3 -std=c++11 -S code.cpp

clang++ --version
    clang version 3.5 (trunk 200620)
    Target: x86_64-apple-darwin13.1.0
    Thread model: posix


Best,
Fernando.
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