Volume 1, Part 2: Memory Reference
1:147
Memory Reference
3
3.1
Overview
Memory latency is a major factor in determining the performance of integer
applications. In order to help reduce the effects of memory latency, the Itanium
architecture explicitly supports software pipelining, large register files, and
compiler-controlled speculation. This chapter discusses features and optimizations
related to compiler-controlled speculation. See
Chapter 5, “Software Pipelining and
for a complete description of how to use software pipelining.
The early sections of this chapter review non-speculative load and store in the Itanium
architecture, and general concepts and terminology related to data dependencies. The
concept of speculation is then introduced, followed by discussions and examples of how
speculation is used. The remainder of this chapter describes several important
optimizations related to memory access and instruction scheduling.
3.2
Non-speculative Memory References
The Itanium architecture supports non-speculative loads and stores, as well as explicit
memory hint instructions.
3.2.1
Stores to Memory
Itanium integer store instructions can write either 1, 2, 4, or 8 bytes and 4, 8, or 10
bytes for floating-point stores. For example, a
st4
instruction will write the first four
bytes of a register to memory.
Although the Itanium architecture uses a little endian memory byte order by default,
software can change the byte order by setting the big endian (be) bit of the user mask
(UM).
3.2.2
Loads from Memory
Itanium integer load instructions can read either 1, 2, 4, or 8 bytes from memory
depending on the type of load issued. Loads of 1, 2, or 4 bytes of data are
zero-extended to 64-bits prior to being written into their target registers.
Although loads are provided for various data types, the basic data type is the quadword
(8 bytes). Apart from a few exceptions, all integer operations are on quadword data.
This can be particularly important when dealing with signed integers and 32-bit
addresses, or any addresses that are shorter than 64 bits.
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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 ...
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Страница 249: ...2 1 Intel Itanium Architecture Software Developer s Manual Rev 2 3 Part I System Architecture Guide ...
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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 ...
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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 ...
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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 ...
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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 ...