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Volume 4: Base IA-32 Instruction Reference
FSTSW/FNSTSW—Store Status Word
Description
Stores the current value of the FPU status word in the destination location. The
destination operand can be either a two-byte memory location or the AX register. The
FSTSW instruction checks for and handles pending unmasked floating-point exceptions
before storing the status word; the FNSTSW instruction does not.
The FNSTSW AX form of the instruction is used primarily in conditional branching (for
instance, after an FPU comparison instruction or an FPREM, FPREM1, or FXAM
instruction), where the direction of the branch depends on the state of the FPU
condition code flags. This instruction can also be used to invoke exception handlers (by
examining the exception flags) in environments that do not use interrupts. When the
FNSTSW AX instruction is executed, the AX register is updated before the processor
executes any further instructions. The status stored in the AX register is thus
guaranteed to be from the completion of the prior FPU instruction.
Operation
DEST
FPUStatusWord;
FPU Flags Affected
The C0, C1, C2, and C3 are undefined.
Floating-point Exceptions
None.
Additional Itanium System Environment Exceptions
Itanium Reg Faults Disabled FP Register Fault if PSR.dfl is 1.
Itanium Mem FaultsVHPT Data Fault, Nested TLB Fault, Data TLB Fault, Alternate Data
TLB Fault, Data Page Not Present Fault, Data NaT Page Consumption
Abort, Data Key Miss Fault, Data Key Permission Fault, Data Access
Rights Fault, Data Access Bit Fault, Data Dirty Bit Fault
Opcode
Instruction
Description
9B DD /7
FSTSW
m2byte
Store FPU status word at
m2byte
after checking for pending
unmasked floating-point exceptions.
9B DF E0
FSTSW AX
Store FPU status word in AX register after checking for pending
unmasked floating-point exceptions.
DD /7
FNSTSW
m2byte
Store FPU status word at
m2byte
without checking for pending
unmasked floating-point exceptions.
DF E0
FNSTSW AX
Store FPU status word in AX register without checking for
pending unmasked floating-point exceptions.
Содержание ITANIUM ARCHITECTURE
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Страница 7: ...402 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Страница 199: ...4 192 Volume 4 Base IA 32 Instruction Reference FWAIT Wait See entry for WAIT ...
Страница 269: ...4 262 Volume 4 Base IA 32 Instruction Reference LES Load Full Pointer See entry for LDS LES LFS LGS LSS ...
Страница 270: ...Volume 4 Base IA 32 Instruction Reference 4 263 LFS Load Full Pointer See entry for LDS LES LFS LGS LSS ...
Страница 273: ...4 266 Volume 4 Base IA 32 Instruction Reference LGS Load Full Pointer See entry for LDS LES LFS LGS LSS ...
Страница 288: ...Volume 4 Base IA 32 Instruction Reference 4 281 LSS Load Full Pointer See entry for LDS LES LFS LGS LSS ...
Страница 352: ...Volume 4 Base IA 32 Instruction Reference 4 345 ROL ROR Rotate See entry for RCL RCR ROL ROR ...
Страница 368: ...Volume 4 Base IA 32 Instruction Reference 4 361 SHL SHR Shift Instructions See entry for SAL SAR SHL SHR ...
Страница 373: ...4 366 Volume 4 Base IA 32 Instruction Reference SIDT Store Interrupt Descriptor Table Register See entry for SGDT SIDT ...
Страница 589: ...4 582 Volume 4 IA 32 SSE Instruction Reference ...
Страница 590: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 Index ...
Страница 591: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Страница 603: ...INDEX Index 12 Index for Volumes 1 2 3 and 4 ...
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