Can C standard library functions with constant argument(s) be executed at compile time?

Question

Can the following code:

float f = sinf(0.5f);

be optimized to the following code (actually pseudocode to give an idea):

float f = 0x1.eaee88p-2f;
feraiseexcept(FE_INEXACT);

The same principle for the other C standard library functions. As I understand, since the "whole language is based on the (rather unhelpful) concept of an "abstract machine" (link), then an "implementation is free to do anything in the ways of optimizations as long as side effects and "the observable behavior" are respected" (the same link).

Answer 1

Some compilers will optimize it to the simple constant expression. It is because the compiler knows how functions from the standard library work. The compiler knows that sinf does not have side effects.

int main(void)
{
    float f = sinf(0.5f);
    printf("%f\n", f);
} 

.LC1:
        .string "%f\n"
main:
        sub     rsp, 8
        mov     edi, OFFSET FLAT:.LC1
        mov     eax, 1
        movsd   xmm0, QWORD PTR .LC0[rip]
        call    printf
        xor     eax, eax
        add     rsp, 8
        ret
.LC0:
        .long   -2147483648
        .long   1071558376