black_box.h

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#pragma once
 
#include "di/meta/operations.h"
#include "di/util/addressof.h"
 
namespace di::util {
template<concepts::CopyConstructible T>
[[gnu::noinline]] auto black_box(T const& value) -> T {
    // We want to produce an identical value from this function, without the compiler realizing it.
    // This is done by passing a pointer through inline assembly, since the compiler won't realize
    // the pointer points to the original object.
    T const* result;
    asm volatile("mov %1, %0\n" : "=r"(result) : "r"(util::addressof(value)) : "memory");
    return *result;
}
}
 
namespace di {
using util::black_box;
}