Re: Floating point constant folding

[Johan Engelen via Digitalmars-d]

On Friday, 3 March 2017 at 09:31:19 UTC, Guillaume Chatelet wrote:

Considering the floating point operations have a runtime component, it seems to me that constant folding is not allowed to occur in the first example. For example, it does not occur in the following C++ snippet:

---
#include <limits>
#include <cstdio>
#include <cfenv>

int main(int, char**) {
    std::fesetround(FE_UPWARD);

printf("%.32g\n", std::numeric_limits<float>::denorm_min() + 1.0f);

    return 0;
}

Clang without/with optimizations turned on:
❯ clang++ float.cpp && ./a.out
1.00000011920928955078125

❯ clang++ float.cpp -O3 && ./a.out
1

-Johan