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Volume 4: Base IA-32 Instruction Reference
FRSTOR—Restore FPU State
Description
Loads the FPU state (operating environment and register stack) from the memory area
specified with the source operand. This state data is typically written to the specified
memory location by a previous FSAVE/FNSAVE 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
®
64 and IA-32
Architectures Software Developer’s Manual
for the layout in memory of the stored
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 contents of the FPU register stack are stored in the
80 bytes immediately follow the operating environment image.
The FRSTOR instruction should be executed in the same operating mode as the
corresponding FSAVE/FNSAVE instruction.
If one or more unmasked exception bits are set in the new FPU status word, a
floating-point exception will be generated. To avoid raising exceptions when loading a
new operating 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);
ST(0)
SRC(ST(0));
ST(1)
SRC(ST(1));
ST(2)
SRC(ST(2));
ST(3)
SRC(ST(3));
ST(4)
SRC(ST(4));
ST(5)
SRC(ST(5));
ST(6)
SRC(ST(6));
ST(7)
SRC(ST(7));
FPU Flags Affected
The C0, C1, C2, C3 flags are loaded.
Floating-point Exceptions
None; however, this operation might unmask an existing exception that has been
detected but not generated, because it was masked. Here, the exception is generated
at the completion of the instruction.
Opcode
Instruction
Description
DD /4
FRSTOR
m94/108byte
Load FPU state from
m94byte
or
m108byte
.
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 ...