Volume 1, Part 1: Application Programming Model
1:55
The 64-bit (
cmp
) and 32-bit (
cmp4
) compare instructions compare two registers, or a
register and an immediate, for one of ten relations (e.g., >, <=). The compare
instructions set two predicate targets according to the result. The
cmp4
instruction
compares the least-significant 32-bits of both sources (the most significant 32-bits are
ignored).
The test bit (
tbit
) instruction sets two predicate registers according to the state of a
single bit in a general register (the position of the bit is specified by an immediate). The
test NaT (
tnat
) instruction sets two predicate registers according to the state of the
NaT bit corresponding to a general register.
The test feature (
tf
) instruction sets two predicate registers according to whether or
not the selected feature is implemented in the processor.
The
fcmp
instruction compares two floating-point registers and sets two predicate
targets according to one of eight relations. The
fclass
instruction sets two predicate
targets according to the classification of the number contained in the floating-point
register source.
The
frcpa
,
fprcpa
,
frsqrta
and
fprsqrta
instructions set a single predicate target if
their floating-point register sources are such that a valid approximation can be
produced, otherwise the predicate target is cleared.
4.3.3
Compare Types
Compare instructions can have as many as five compare types: Normal, Unconditional,
AND, OR, or DeMorgan. The type defines how the instruction writes its target predicate
registers based on the outcome of the comparison and on the qualifying predicate. The
description of these types is contained in
. In the table, “qp” refers to the
value of the qualifying predicate of the compare and “result” refers to the outcome of
the compare relation (one if the compare relation is true and zero if the compare
relation is false).
The Normal compare type simply writes the compare result to the first predicate target
and the complement of the result to the second predicate target.
Table 4-9.
Compare Type Function
Compare Type
Completer
Operation
First Predicate Target
Second Predicate Target
Normal
none
if (qp) {target = result}
if (qp) {target =!result}
Unconditional
unc
if (qp) {target = result}
else {target = 0}
if (qp) {target =!result}
else {target = 0}
AND
and
if (qp &&!result) {target = 0}
if (qp &&!result) {target = 0}
andcm
if (qp && result) {target = 0}
if (qp && result) {target = 0}
OR
or
if (qp && result) {target = 1}
if (qp && result) {target = 1}
orcm
if (qp &&!result) {target = 1}
if (qp &&!result) {target = 1}
DeMorgan
or.andcm
if (qp && result) {target = 1}
if (qp && result) {target = 0}
and.orcm
if (qp &&!result) {target = 0}
if (qp &&!result) {target = 1}
Содержание ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS VOLUME 3 REV 2.3
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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 ...
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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 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 ...
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Страница 1099: ...3 200 Volume 3 Instruction Reference padd Interruptions Illegal Operation fault ...
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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 ...