2:512
Volume 2, Part 2: MP Coherence and Synchronization
• Global visibility order of memory operations (
and
This presentation is organized to begin with simple behaviors and move to increasingly
complex behaviors.
2.2.1.1
Assumptions and Notation
The discussions of the multiprocessor executions in the upcoming sections adopt two
main notational conventions.
First, the memory accesses in the executions in this document are written using a
pseudo-Itanium architecture-based assembly language that allows a store to write an
immediate operand to memory. All memory locations are cacheable and aligned. Unless
stated otherwise, memory locations do not overlap. Initially, all registers and memory
locations contain zero.
Second, given two different memory operations X and Y,
specifies that X precedes
Y in program order and
indicates that X is visible if Y is visible (i.e. X becomes
visible before Y).
Using this notation,
expresses the Itanium ordering semantics from
Section 2.1.1, “Memory Ordering of Cacheable Memory References” on page 2:507
and
Section 4.4.7, “Memory Access Ordering” on page 1:73
. There are no implications
regarding the ordering of the visibility for the following pairs of operations: a release
followed by an unordered operation; a release followed by an acquire; an unordered
operation followed by another; or an unordered operation followed by an acquire.
, “Acquire”, “Release”, and “Fence” represent an orderable instruction with
the corresponding memory ordering semantics whereas “X” and “Y” indicate any
orderable instruction.
2.2.1.2
The Intel
®
Itanium
®
Architecture Provides a Relaxed Ordering Model
The Itanium memory ordering model is a relaxed model. As a result, the Itanium
architecture permits any outcome when executing the code shown in
Figure 2-1.
Intel
®
Itanium
®
Ordering Semantics
Table 2-1.
Intel
®
Itanium
®
Architecture Provides a Relaxed Ordering
Model
Processor #0
Processor #1
st
[x] = 1
// M1
st
[y] = 1
// M2
ld
r1 = [y]
// M3
ld
r2 = [x]
// M4
Outcomes:
all are allowed
X Y
»
X
Y
Acquire X
Acquire
X
»
X Release
X
Release
»
X Fence
X
Fence
»
Fence Y
Fence
Y
»
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 ...