x86 Instruction Set Reference

Extracts the sign bits from the packed double-precision floating-point values in the source operand (second operand), formats them into a 2-bit mask, and stores the mask in the destination operand (first operand). The source operand is an XMM register, and the destination operand is a general-purpose register. The mask is stored in the 2 low-order bits of the destination operand.

Destination[0] = Source[63];
Destination[1] = Source[127];
Destination[2..3] = 0;
Destination[4..31] = 0;