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Volume 4: IA-32 SSE Instruction Reference
COMISS: Scalar Ordered Single-FP Compare and set EFLAGS
Operation:
switch (xmm1[31-0] <> xmm2/m32[31-0]) {
OF,SF,AF = 000;
case UNORDERED: ZF,PF,CF = 111;
case GREATER_THAN: ZF,PF,CF = 000;
case LESS_THAN: ZF,PF,CF = 001;
case EQUAL: ZF,PF,CF = 100;
}
Description:
The COMISS instructions compare two SP FP numbers and sets the ZF,PF,CF bits in the
EFLAGS register as described above. Although the data type is packed single-FP, only
the lower SP numbers are compared. 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).
FP Exceptions:
None.
Numeric Exceptions:
Invalid (if SNaN or QNaN operands), Denormal. Integer EFLAGS values will not be
updated in the presence of unmasked numeric exceptions.
Protected Mode Exceptions:
#GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS or GS
segments; #SS(0) for an illegal address in the SS segment; #PF (fault-code) for a page
fault; #UD if CR0.EM = 1; #NM if TS bit in CR0 is set; #AC for unaligned memory
reference. To enable #AC exceptions, three conditions must be true(CR0.AM is set;
EFLAGS.AC is set; current CPL is 3); #XM for an unmasked SSE numeric exception
(CR4.OSXMMEXCPT =1); #UD for an unmasked SSE numeric exception
(CR4.OSXMMEXCPT =0); #UD if CRCR4.OSFXSR(bit 9) = 0; #UD if CPUID.XMM(EDX
bit 25) = 0.
Real Address Mode Exceptions:
Interrupt 13 if any part of the operand would lie outside of the effective address space
from 0 to 0FFFFH;
#UD if CR0.EM = 1; #NM if TS bit in CR0 is set; #XM for an
unmasked SSE numeric exception (CR4.OSXMMEXCPT =1); #UD for an unmasked SSE
numeric exception (CR4.OSXMMEXCPT =0); #UD if CRCR4.OSFXSR(bit 9) = 0; #UD if
CPUID.XMM(EDX bit 25) = 0.
Virtual 8086 Mode Exceptions:
Same exceptions as in Real Address Mode; #AC for unaligned memory reference if the
current privilege level is 3; #PF (fault-code) for a page fault.
Opcode
Instruction
Description
0F,2F,/r
COMISS 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
Summary of Contents for ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS VOLUME 3 REV 2.3
Page 1: ......
Page 11: ...x Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 13: ...1 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 33: ...1 22 Volume 1 Part 1 Introduction to the Intel Itanium Architecture ...
Page 57: ...1 46 Volume 1 Part 1 Execution Environment ...
Page 147: ...1 136 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 149: ...1 138 Volume 1 Part 2 About the Optimization Guide ...
Page 191: ...1 180 Volume 1 Part 2 Predication Control Flow and Instruction Stream ...
Page 230: ......
Page 248: ...236 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 250: ...2 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 264: ...2 16 Volume 2 Part 1 Intel Itanium System Environment ...
Page 380: ...2 132 Volume 2 Part 1 Interruptions ...
Page 398: ...2 150 Volume 2 Part 1 Register Stack Engine ...
Page 486: ...2 238 Volume 2 Part 1 IA 32 Interruption Vector Descriptions ...
Page 750: ...2 502 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 754: ...2 506 Volume 2 Part 2 About the System Programmer s Guide ...
Page 796: ...2 548 Volume 2 Part 2 Interruptions and Serialization ...
Page 808: ...2 560 Volume 2 Part 2 Context Management ...
Page 842: ...2 594 Volume 2 Part 2 Floating point System Software ...
Page 850: ...2 602 Volume 2 Part 2 IA 32 Application Support ...
Page 862: ...2 614 Volume 2 Part 2 External Interrupt Architecture ...
Page 870: ...2 622 Volume 2 Part 2 Performance Monitoring Support ...
Page 891: ......
Page 1099: ...3 200 Volume 3 Instruction Reference padd Interruptions Illegal Operation fault ...
Page 1295: ...3 396 Volume 3 Resource and Dependency Semantics ...
Page 1296: ......
Page 1302: ...402 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 1494: ...4 192 Volume 4 Base IA 32 Instruction Reference FWAIT Wait See entry for WAIT ...
Page 1647: ...Volume 4 Base IA 32 Instruction Reference 4 345 ROL ROR Rotate See entry for RCL RCR ROL ROR ...
Page 1884: ...4 582 Volume 4 IA 32 SSE Instruction Reference ...
Page 1885: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 Index ...
Page 1886: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 1898: ...INDEX Index 12 Index for Volumes 1 2 3 and 4 ...