3-690
INSTRUCTION SET REFERENCE
UCOMISS—Unordered Scalar Single-FP compare and set EFLAGS
Description
The UCOMISS instructions compare the two lowest scalar SP FP numbers, and set the ZF,PF,CF
bits in the EFLAGS register as described above. In addition, the OF, SF, and AF bits in the
EFLAGS register are zeroed out. The unordered predicate is returned if either source operand is
a NaN (qNaN or sNaN).
Figure 3-95. Operation of the UCOMISS Instruction, Condition One
EFLAGS: OF,SF,AF=000
EFLAGS: ZF,PF,CF=111
MXCSR flags: Invalid flag is set
OpcodeInstruction
Description
0F,2E,/rUCOMISS xmm1,
xmm2/m32
Compare lower SP FP number in XMM1 register with lower SP FP
number in XMM2/Mem and set the status flags accordingly.
Xmm1
Xmm2/
m32
Xmm1
=
=
=
=
