User Guide

172 128-Bit Media and Scientific Programming

AMD64 Technology 24592—Rev. 3.15—November 2009

• CMPPD—Compare Packed Double-Precision Floating-Point

• CMPSS—Compare Scalar Single-Precision Floating-Point

• CMPSD—Compare Scalar Double-Precision Floating-Point

The CMPPS instruction compares each of four single-precision floating-point values in the first

operand with the corresponding single-precision floating-point value in the second operand and writes

the result in the corresponding 32 bits of the destination. The type of comparison is specified by the

three low-order bits of the immediate-byte operand. The result of each compare is a 32-bit value of all

1s (TRUE) or all 0s (FALSE). Some compare operations that are not directly supported by the

immediate-byte encodings can be implemented by swapping the contents of the source and destination

operands before executing the compare.

The CMPPD instruction performs an analogous operation for two double-precision floating-point

values. The CMPSS instruction performs an analogous operation for the single-precision floating-

point values in the low-order 32 bits of the source operands. The three high-order doublewords of the

destination are not modified. The CMPSD instruction performs an analogous operation for the double-

precision floating-point values in the low-order 64 bits of the source operands. The high-order 64 bits

of the destination XMM register are not modified.

Figure 4-36 shows a CMPPD compare operation.

Figure 4-36. CMPPD Compare Operation

Compare and Write Minimum or Maximum

• MAXPS—Maximum Packed Single-Precision Floating-Point

• MAXPD—Maximum Packed Double-Precision Floating-Point

• MAXSS—Maximum Scalar Single-Precision Floating-Point

513-162.eps

result

operand 1

127 0

operand 2

127 0

imm8

compare

all 1s or 0s all 1s or 0s

compare