2:94
Volume 2, Part 1: Addressing and Protection
boundaries respectively to avoid generation of an Unaligned Data Reference fault.
When PSR.ac is 1, any IA-32 data memory reference that is not aligned on a boundary
the size of the operand results in an IA_32_Exception(AlignmentCheck) fault.
Note:
10-byte and floating-point load double pair datum alignment is 16-bytes. The
alignment of long format 32-byte VHPT references is always 32-bytes.
Unaligned Itanium semaphore references (
cmpxchg
,
xchg
,
fetchadd
) result in an
Unaligned Data Reference fault regardless of the state of PSR.ac. For the
cmp8xchg16
instruction, the address specified must be 8-byte aligned.
When PSR.ac is 0, Itanium data memory references that are not aligned may or may
not result in an Unaligned Data Reference fault based on the implementation. The level
of unaligned memory support is implementation specific. However, all implementations
will raise an Unaligned Data Reference fault if the datum referenced by an Itanium
instruction spans a 4K aligned boundary, and many implementations will raise an
Unaligned Data Reference fault if the datum spans a cache line. Implementations may
also raise an Unaligned Data Reference fault for any other unaligned Itanium memory
reference. Software is strongly encouraged to align data values to avoid possible
performance degradation for both IA-32 and Itanium architecture-based code. When
PSR.ac is 0 and IA-32 alignment checks are also disabled, no fault is raised regardless
of alignment for IA-32 data memory references.
Unaligned advanced loads are supported, though a particular implementation may
choose not to allocate an ALAT entry for an unaligned advanced load. Additionally, the
ALAT may “pessimistically” allocate an entry for an unaligned load by allocating a larger
entry than the natural size of the datum being loaded, as long as the larger entry
completely covers the unaligned address range (e.g. a
ld4.a
to address 0x3 may
allocate an 8-byte entry starting at address 0x0). Stores (unaligned or otherwise) may
also pessimistically invalidate unaligned ALAT entries.
§
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 ...