Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 1445

FLDENV—Load FPU Environment
Opcode
D9 /4
Description
Loads the complete FPU operating environment from memory into the FPU registers.
The source operand specifies the first byte of the operating-environment data in
memory.This data is typically written to the specified memory location by a FSTENV or
FNSTENV instruction.
The FPU operating environment consists of the FPU control word, status word, tag
word, instruction pointer, data pointer, and last opcode. See the Intel
Architectures Software Developer's Manual for the layout in memory of the loaded
environment, depending on the operating mode of the processor (protected or real)
and the size of the current address attribute (16-bit or 32-bit). In virtual-8086 mode,
the real mode layouts are used.
The FLDENV instruction should be executed in the same operating mode as the
corresponding FSTENV/FNSTENV instruction.
If one or more unmasked exception flags are set in the new FPU status word, a
floating-point exception will be generated upon execution of the next floating-point
instruction (except for the no-wait floating-point instructions. To avoid generating
exceptions when loading a new environment, clear all the exception flags in the FPU
status word that is being loaded.
Operation
FPUControlWord  SRC(FPUControlWord);
FPUStatusWord  SRC(FPUStatusWord);
FPUTagWord  SRC(FPUTagWord);
FPUDataPointer  SRC(FPUDataPointer);
FPUInstructionPointer  SRC(FPUInstructionPointer);
FPULastInstructionOpcode  SRC(FPULastInstructionOpcode);
FPU Flags Affected
The C0, C1, C2, C3 flags are loaded.
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
Floating-point Exceptions
None; however, if an unmasked exception is loaded in the status word, it is generated
upon execution of the next waiting floating-point instruction.
Volume 4: Base IA-32 Instruction Reference
Instruction Description
FLDENV m14/28byte Load FPU environment from m14byte or m28byte.
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
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64 and IA-32
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