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Volume 4: IA-32 SSE Instruction Reference
4:479
In the extreme case, all the significant bits are shifted out to the right by leading zeros,
creating a zero result.
The processor deals with denormal values in the following ways:
• It avoids creating denormals by normalizing numbers whenever possible.
• It provides the floating-point underflow exception to permit programmers to detect
cases when denormals are created.
• It provides the floating-point denormal-operand exception to permit procedures or
programs to detect when denormals are being used as source operands for
computations.
4.7.1.7
Signed Infinities
The two infinities, +
and
, represent the maximum positive and negative real
numbers, respectively, that can be represented in the floating-point format. Infinity is
always represented by a zero significand (fraction and integer bit) and the maximum
biased exponent allowed in the specified format (for example, 255
10
for the single-real
format).
The signs of infinities are observed, and comparisons are possible. Infinities are always
interpreted in the affine sense; that is, -
is less than any finite number and +
is
greater than any finite number. Arithmetic on infinities is always exact. Exceptions are
generated only when the use of an infinity as a source operand constitutes an invalid
operation.
Whereas denormalized numbers represent an underflow condition, the two infinity
numbers represent the result of an overflow condition. Here, the normalized result of a
computation has a biased exponent greater than the largest allowable exponent for the
selected result format.
4.7.1.8
NaNs
Since NaNs are non-numbers, they are not part of the real number line. In
the encoding space for NaNs in the processor floating-point formats is shown above the
ends of the real number line. This space includes any value with the maximum
allowable biased exponent and a non-zero fraction. (The sign bit is ignored for NaNs.)
The IEEE standard defines two classes of NaN: quiet NaNs (QNaNs) and signaling NaNs
(SNaNs). A QNaN is a NaN with the most significant fraction bit set; an SNaN is a NaN
with the most significant fraction bit clear. QNaNs are allowed to propagate through
most arithmetic operations without signaling an exception. SNaNs generally signal an
invalid-operation exception whenever they appear as operands in arithmetic operations.
Exceptions, as well as detailed information on how the processor handles NaNs, are
discussed in Section 4.7.2, “Operating on NaNs”.
Denormalize
0
126
0.00101011100...00
Denormal Result
0
126
0.00101011100...00
a. Expressed as an unbiased, decimal number.
Table 4-2.
Denormalization Process
Operation
Sign
Exponent
a
Significand
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 ...
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 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 ...
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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 ...
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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 ...