Performs an SIMD compare of the four packed singleprecision floatingpoint values in the source operand (second operand) and the destination operand (first operand) and returns the results of the comparison to the destination operand. The comparison predicate operand (third operand) specifies the type of comparison performed on each of the pairs of packed values. The result of each comparison is a doubleword mask of all 1s (comparison true) or all 0s (comparison false). The source operand can be an XMM register or a 128bit memory location. The destination operand is an XMM register. The comparison predicate operand is an 8bit immediate the first 3 bits of which define the type of comparison to be made (see the following table); bits 4 through 7 of the immediate are reserved.
The unordered relationship is true when at least one of the two source operands being compared is a NaN; the ordered relationship is true when neither source operand is a NaN.
A subsequent computational instruction that uses the mask result in the destination operand as an input operand will not generate a fault, because a mask of all 0s corresponds to a floatingpoint value of +0.0 and a mask of all 1s corresponds to a QNaN.
Some of the comparisons listed in the following table (such as the greaterthan, greaterthanorequal, notgreater than, and notgreaterthanorequal relations) can be made only through software emulation.
For these comparisons the program must swap the operands (copying registers when necessary to protect the data that will now be in the destination), and then perform the compare using a different predicate. The predicate to be used for these emulations is listed in the following table under the heading Emulation.
Compilers and assemblers may implement the following twooperand pseudoops in addition to the threeoperand CMPPS instruction. See the following table.
PseudoOp  Implementation 
CMPEQPS xmm1, xmm2  CMPPS xmm1, xmm2, 0 
CMPLTPS xmm1, xmm2  CMPPS xmm1, xmm2, 1 
CMPLEPS xmm1, xmm2  CMPPS xmm1, xmm2, 2 
CMPUNORDPS xmm1, xmm2  CMPPS xmm1, xmm2, 3 
CMPNEQPS xmm1, xmm2  CMPPS xmm1, xmm2, 4 
CMPNLTPS xmm1, xmm2  CMPPS xmm1, xmm2, 5 
CMPNLEPS xmm1, xmm2  CMPPS xmm1, xmm2, 6 
CMPORDPS xmm1, xmm2  CMPPS xmm1, xmm2, 7 
The greaterthan relations not implemented by the processor require more than one instruction to emulate in software and therefore should not be implemented as pseudoops. (For these, the programmer should reverse the operands of the corresponding less than relations and use move instructions to ensure that the mask is moved to the correct destination register and that the source operand is left intact.)
