Binder Manual (G06.24+, H06.03+)

Introduction

Binder Manual—528613-003

1-6

The Object Code Accelerator (OCA)

This section contains a general introduction to OCA; for more details see the Object

Code Accelerator Manual.

OCA processes TNS object code to produce accelerated object code. On TNS/E

systems, accelerated object code runs significantly faster than TNS object code.

OCA takes as input an executable TNS object file and produces as output an

accelerated object file. The accelerated object file contains both the original TNS code,

and the logically equivalent optimized Itanium instructions (accelerated object code).

This process is illustrated in Figure 1-3, The Acceleration Process.

For each TNS instruction OCA produces its functional equivalent on the TNS/E

system, in the form of either:

•

A sequence of zero or more (usually more than one) Itanium instructions

•

A call on a millicode routine

In the first and more common case, OCA treats a TNS instruction as though it were a

macro instruction, expanding it into Itanium instructions. In the second case, OCA

treats a TNS instruction as though it were a call on a closed subroutine, referred to as

a millicode routine. Millicode routines are sets of Itanium instructions that implement

various complex TNS instructions and low-level functions such as exception handling,

real-time translation routines, and floating-point and quad arithmetic. Millicode is

functionally equivalent to TNS microcode.

OCA can produce only optimized Itanium instructions for TNS instruction sequences

whose exact meaning can be determined before runtime. When the exact meaning

cannot be determined until run time, the program makes a transition into TNS code

and executes the original TNS instructions.

Figure 1-3. The Acceleration Process

Accelerated Object File

TNS

Compiler

TNS

Object Code

TNS Object File

OCA

TNS

Object Code

Accelerated

Object Code

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