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2:596
Volume 2, Part 2: IA-32 Application Support
9.1
Transitioning between Intel
®
Itanium
®
and IA-32
Instruction Sets
As mentioned earlier, user-level code can transition from Itanium to IA-32 (or back)
instruction sets without operating system intervention. As described in
“IA-32 Application Execution Model in an Intel
, two instructions are provided for this purpose:
br.ia
(an Itanium
unconditional branch), and JMPE (an IA-32 register indirect and absolute jump). Prior
to executing any IA-32 instructions, however, the Itanium architecture-based operating
system needs to setup an execution environment for executing IA-32 code.
9.1.1
IA-32 Code Execution Environments
Processors based on the Itanium architecture are capable of executing IA-32 code in
real mode, VM86 mode or protected mode. When segmentation is enabled both 16 and
32-bit code are supported. Prior to transferring control to IA-32 code, an Itanium
architecture-based application and/or operating system is expected to setup the
complete IA-32 execution environment in Itanium registers.
In particular, Itanium architecture-based software must setup IA-32 segment descriptor
and selector registers in Itanium application registers, and must ensure that code and
stack segment descriptors (CSD, SSD) are pointing at valid and correctly aligned
memory areas. It is also worth noting that the IA-32 GDT and LDT descriptors are
maintained in GR30 and GR31, and are unprotected from Itanium architecture-based
user-level code. For more details on the IA-32 execution environment please refer to
Section 6.2.2, “IA-32 Application Register State Model” on page 1:113
.
Some IA-32 execution environments may need support from an Itanium
architecture-based operating system. Which IA-32 software environments are
supported by an Itanium architecture-based operating system is determined by the
operating system vendor. Itanium architecture-based platform firmware (SAL) provides
a runtime environment that allows execution of real-mode IA-32 code found in PCI
configuration option ROMs.
9.1.2
br.ia
br.ia
is an unconditional indirect branch that transitions from Itanium to IA-32
instruction set. Prior to entering IA-32 code with
br.ia
, software is also required to
flush the register stack.
br.ia
sets the size of the current register stack frame to zero.
The register stack is disabled during IA-32 code execution. Because IA-32 code
execution uses Itanium registers, much of the Itanium register state is overwritten and
left in an undefined state when IA-32 code is run. As a result, software can not rely on
the value of such registers across an instruction set transition. Execution of IA-32 code
also invalidates the ALAT. For more details refer to
Содержание ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS VOLUME 3 REV 2.3
Страница 1: ......
Страница 11: ...x Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Страница 12: ...1 1 Intel Itanium Architecture Software Developer s Manual Rev 2 3 Part I Application Architecture Guide ...
Страница 13: ...1 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Страница 33: ...1 22 Volume 1 Part 1 Introduction to the Intel Itanium Architecture ...
Страница 57: ...1 46 Volume 1 Part 1 Execution Environment ...
Страница 147: ...1 136 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Страница 149: ...1 138 Volume 1 Part 2 About the Optimization Guide ...
Страница 191: ...1 180 Volume 1 Part 2 Predication Control Flow and Instruction Stream ...
Страница 230: ......
Страница 248: ...236 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Страница 249: ...2 1 Intel Itanium Architecture Software Developer s Manual Rev 2 3 Part I System Architecture Guide ...
Страница 250: ...2 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Страница 264: ...2 16 Volume 2 Part 1 Intel Itanium System Environment ...
Страница 380: ...2 132 Volume 2 Part 1 Interruptions ...
Страница 398: ...2 150 Volume 2 Part 1 Register Stack Engine ...
Страница 486: ...2 238 Volume 2 Part 1 IA 32 Interruption Vector Descriptions ...
Страница 749: ...2 501 Intel Itanium Architecture Software Developer s Manual Rev 2 3 Part II System Programmer s Guide ...
Страница 750: ...2 502 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Страница 754: ...2 506 Volume 2 Part 2 About the System Programmer s Guide ...
Страница 796: ...2 548 Volume 2 Part 2 Interruptions and Serialization ...
Страница 808: ...2 560 Volume 2 Part 2 Context Management ...
Страница 842: ...2 594 Volume 2 Part 2 Floating point System Software ...
Страница 850: ...2 602 Volume 2 Part 2 IA 32 Application Support ...
Страница 862: ...2 614 Volume 2 Part 2 External Interrupt Architecture ...
Страница 870: ...2 622 Volume 2 Part 2 Performance Monitoring Support ...
Страница 891: ......
Страница 941: ...3 42 Volume 3 Instruction Reference cmp illegal_operation_fault PR p1 0 PR p2 0 Interruptions Illegal Operation fault ...
Страница 1099: ...3 200 Volume 3 Instruction Reference padd Interruptions Illegal Operation fault ...
Страница 1191: ...3 292 Volume 3 Pseudo Code Functions Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Страница 1295: ...3 396 Volume 3 Resource and Dependency Semantics ...
Страница 1296: ......
Страница 1302: ...402 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Страница 1494: ...4 192 Volume 4 Base IA 32 Instruction Reference FWAIT Wait See entry for WAIT ...
Страница 1564: ...4 262 Volume 4 Base IA 32 Instruction Reference LES Load Full Pointer See entry for LDS LES LFS LGS LSS ...
Страница 1565: ...Volume 4 Base IA 32 Instruction Reference 4 263 LFS Load Full Pointer See entry for LDS LES LFS LGS LSS ...
Страница 1568: ...4 266 Volume 4 Base IA 32 Instruction Reference LGS Load Full Pointer See entry for LDS LES LFS LGS LSS ...
Страница 1583: ...Volume 4 Base IA 32 Instruction Reference 4 281 LSS Load Full Pointer See entry for LDS LES LFS LGS LSS ...
Страница 1647: ...Volume 4 Base IA 32 Instruction Reference 4 345 ROL ROR Rotate See entry for RCL RCR ROL ROR ...
Страница 1663: ...Volume 4 Base IA 32 Instruction Reference 4 361 SHL SHR Shift Instructions See entry for SAL SAR SHL SHR ...
Страница 1668: ...4 366 Volume 4 Base IA 32 Instruction Reference SIDT Store Interrupt Descriptor Table Register See entry for SGDT SIDT ...
Страница 1884: ...4 582 Volume 4 IA 32 SSE Instruction Reference ...
Страница 1885: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 Index ...
Страница 1886: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Страница 1898: ...INDEX Index 12 Index for Volumes 1 2 3 and 4 ...