Feature request: function to detect Invariant TSC

SDL Development
1

Please add SDL_HasInvariantTSC function with which I can find out if the Invariant TSC is supported.

Or you can go Linux way and add two functions:
SDL_HasConstantTSC and SDL_HasNonstopTSC

Basically, Invariant TSC = Constant TSC and Non-stop TSC

Reference implementation:

/* http://www.mkurnosov.net/uploads/Main/mkurnosov-rdtsc-2014.pdf */
/* is_tsc_invariant: Returns 1 if TSC is invariant. */
int is_tsc_invariant()
{
    uint32_t edx;
    __asm__ __volatile__(
        "movl $0x80000007, %%eax\n"
        "cpuid\n"
        "movl %%edx, %0\n"
        : "=r" (edx) /* Output */
        : /* Input */
        : "%rax", "%rbx", "%rcx", "%rdx" /* Clobbered registers */
    );
    return edx & (1U << 8) ? 1 : 0;
}