IEEE 754: is v *= -1 always guaranteed to be the same as v = -v?

Question

Is it guaranteed by standards (IEEE 754 / C) that in the following code assertion will never be failed?

int main()
{
    for ( /* all possible float / double values */ )
    {
        v_neg1 = v * -1;
        v_neg2 = -v;
        assert( v_neg1 == v_neg2 );
    }
    return 0;
}

UPD.

1. When asking I've meant all possible float / double values excluding NaNs.
2. See similar question: .NET decimal.Negate vs multiplying by -1

Answer 1

No, this is not necessarily true, because NaNs never compare equal to each other.

Other than that, given that the sign bit is independent of the exponent and absolute significand, I believe it to be true for all ordinary values. C refers to ISO/IEC 60559 / IEEE 754 appendix; unfortunately I do not have the standard myself.

#include <math.h>
#include <assert.h>


int main(void)
{
    double v, v_neg1, v_neg2;

    v = NAN;
    v_neg1 = v * -1;
    v_neg2 = -v;
    assert( v_neg1 == v_neg2 );
}