Fun with x87 instructions using inline assembly (Intel syntax)

fun.cc

// g++ fun.cc -masm=intel

float fpzero = 0;
unsigned long pfpzero = (unsigned long)&fpzero;
__asm__ volatile("xorps xmm1, xmm1");
__asm__ volatile("fldpi"); // load PI
__asm__ volatile("fchs");  // change sign
__asm__ volatile("fst dword ptr [%0]":"=&r"(pfpzero));    

// this should be -3.14159...
std::cout << fpzero << std::endl;