148
Execution Unit Resources
AMD Athlon™ Processor x86 Code Optimization
22007E/0—November 1999
Execution Unit Resources
Terminology
The execution units operate with two types of register values —
operands and results. There are three operand types and two
result types, which are described in this section.
Operands
The three types of operands are as follows:
■
Address register operands—Used for address calculations of
load and store instructions
■
Data register operands—Used for register instructions
■
Store data register operands—Used for memory stores
Results
The two types of results are as follows:
■
Data register results—Produced by load or register
instructions
■
Address register results—Produced by LEA or PUSH
instructions
Examples
The following examples illustrate the operand and result
definitions:
ADD
EAX, EBX
The ADD instruction has two data register operands (EAX
and EBX) and one data register result (EAX).
MOV
EBX, [ESP+4*ECX+8]
;Load
The Load instruction has two address register operands
(ESP and ECX as base and index registers, respectively)
and a data register result (EBX).
MOV
[ESP+4*ECX+8], EAX
;Store
The Store instruction has a data register operand (EAX)
and two address register operands (ESP and ECX as base
and index registers, respectively).
LEA
ESI, [ESP+4*ECX+8]
The LEA instruction has address register operands (ESP
and ECX as base and index registers, respectively), and an
address register result (ESI).
Summary of Contents for Athlon Processor x86
Page 1: ...AMD Athlon Processor x86 Code Optimization Guide TM...
Page 12: ...xii List of Figures AMD Athlon Processor x86 Code Optimization 22007E 0 November 1999...
Page 16: ...xvi Revision History AMD Athlon Processor x86 Code Optimization 22007E 0 November 1999...
Page 202: ...186 Page Attribute Table PAT AMD Athlon Processor x86 Code Optimization 22007E 0 November 1999...
Page 252: ...236 VectorPath Instructions AMD Athlon Processor x86 Code Optimization 22007E 0 November 1999...
Page 256: ...240 Index AMD Athlon Processor x86 Code Optimization 22007E 0 November 1999...