Volume 2, Part 2: Runtime Support for Control and Data Speculation
2:581
• ITLB.ed=0 (no control speculative recovery code): The compiler generates recovery
code only for ld.sa and ld.a instructions that have speculatively executed uses.
Speculation failure of
ld.sa
and
ld.a
instructions that have no speculatively
executed uses can be recovered by a
ld.c
instruction, and hence do not require
recovery code. Speculation failure of
ld.s
instructions does not require recovery
code, because, in this model, the operating system must guarantee that only fatal
exceptions will be deferred. This requires software-only deferral of all potential
non-fatal exceptions. The motivation for this model is that the absence of
chk.s
instructions and their associated recovery code may make for shorter and more
compact in-line code, especially in loops with tight instruction schedules.
Presence or lack of control speculation recovery code is communicated from the
compiler and the runtime system to the operating system by marking the code page’s
page table entry ed-bit appropriately (this bit is referred to as ITLB.ed). When ITLB.ed
is 1, the operating system will expect recovery code to be present; when ITLB.ed is 0
no recovery code is expected. When a control speculative load takes an exception, the
code page’s ITLB.ed bit is copied into ISR.ed and is made available to the operating
system exception handler. Furthermore, a set ISR.sp bit indicates that an exception was
caused by a control speculative load.
6.3
Speculation Related Exception Handlers
6.3.1
Unaligned Handler
Misaligned control and data speculative loads, as well as architectural loads, are not
required to be handled by the processor. As a result, the operating system’s unaligned
reference handler has to be prepared to emulate such misaligned memory references,
especially in cases where the application has not provided any recovery code (see
for details). Furthermore, misaligned data speculative loads (
ld.sa
or
ld.a
) must be forced failed by the unaligned emulation handler, because the ALAT
cannot track all sizes of misalignment for store conflict detection.
Table 6-1.
Speculation Recovery Code Requirements
Usage Model
OS May Defer Non-fatal Exceptions
on Control Speculative Loads
(ITLB.ed=1)
OS Must Not Defer Non-fatal
Exceptions on Control
Speculative Loads
(ITLB.ed=0)
No Speculative Load Uses
ld.s
Recovery code required; Invoked by
chk.s
or non-speculative use of
speculative value recovers from failed
control speculation.
No recovery code required;
OS handles all non-fatal exceptions
speculatively.
ld.sa,ld.a
No recovery code required;
ld.c
recovers from failed data speculation.
With Speculative Load Uses
ld.s
Recovery code required; invoked by
chk.s
or non-speculative use of
speculative value recovers from failed
control speculation.
No recovery code required;
OS handles all non-fatal exceptions
speculatively.
ld.sa,ld.a
Recovery code required;
chk.a
recovers from failed data speculation.
Содержание ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS VOLUME 3 REV 2.3
Страница 1: ......
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 ...
Страница 230: ......
Страница 248: ...236 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Страница 249: ...2 1 Intel Itanium Architecture Software Developer s Manual Rev 2 3 Part I System Architecture Guide ...
Страница 250: ...2 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
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 ...
Страница 750: ...2 502 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
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 ...
Страница 862: ...2 614 Volume 2 Part 2 External Interrupt Architecture ...
Страница 870: ...2 622 Volume 2 Part 2 Performance Monitoring Support ...
Страница 891: ......
Страница 941: ...3 42 Volume 3 Instruction Reference cmp illegal_operation_fault PR p1 0 PR p2 0 Interruptions Illegal Operation fault ...
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 ...
Страница 1296: ......
Страница 1302: ...402 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
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 ...