Ia-32 Execution Layer; Hardware-Based Ia-32 Application Execution - Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual

IA-32 Application Execution Model in an
®
Intel Itanium
IA-32 application execution on Itanium-based systems may be supported with IA-32
Execution Layer, an OS-based optimizing binary translator, or processor
hardware-based execution. The implementation of IA-32 application execution on a
platform is transparent to IA-32 applications and does not require any application
modification.
6.1

IA-32 Execution Layer

IA-32 Execution Layer provides operating systems with optimizing dynamic binary
translation to accelerate legacy IA-32 application performance relative to
hardware-based execution. When installed, IA-32 Execution Layer supersedes
hardware-based execution of IA-32 applications.
The operating system loads IA-32 Execution Layer into user space, where it executes
using application virtual space and privilege level. IA-32 Execution Layer uses the
native OS for acquiring system resources (memory, synchronization objects, etc.),
executing 32-bit system calls issued by the IA-32 application, signal handling,
exceptions, and other system notifications.
IA-32 Execution Layer supports user-mode, 32-bit-flat-protected applications.
Consistent with Itanium-based operating systems that support legacy IA-32
applications, 16-bit applications and applications containing 32-bit device drivers are
not supported.
6.2

Hardware-based IA-32 Application Execution

This section describes the IA-32 execution model from the perspective of an application
programmer using the Itanium architecture, interfacing with IA-32 code, while
operating in the Itanium System Environment. The main features covered are:
• IA-32 integer, segment, floating-point, MMX technology, and SSE register state
mappings
• Instruction set transitions
• IA-32 memory and addressing model overview
This section does not cover the details of IA-32 application programming model, IA-32
instructions and registers. Refer to the Intel
Developer's Manual for details regarding IA-32 application programming model.
Volume 1, Part 1:IA-32 Application Execution Model in an Intel
®
System Environment
®
Itanium
®
64 and IA-32 Architectures Software
®
System Environment
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