Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 1783
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Table 4-3.
An SNaN and a QNaN.
Two SNaNs.
Two QNaNs.
An SNaN and a real value.
A QNaN and a real value.
An SNaN/QNaN value (for instructions
which take only one operand i.e.
RCPPS, RCPSS, RSQRTPS,
RSQRTSS)
Neither source operand is a NaN and a
floating-point invalid-operation
exception is signaled.
4.8
Data Formats
4.8.1
Memory Data Formats
The Intel SSE architecture introduces a new packed 128-bit data type which consists of
4 single-precision floating-point numbers. The 128 bits are numbered 0 through 127.
Bit 0 is the least significant bit (LSB), and bit 127 is the most significant bit (MSB).
Bytes in the new data type format have consecutive memory addresses. The ordering is
always little endian, that is, the bytes with the lower addresses are less significant than
the bytes with the higher addresses.
Figure 4-11.
Byte 15
Memory Address 1016d
4.8.2
SSE Register Data Formats
Values in SSE registers have the same format as a 128-bit quantity in memory. They
have two data access modes: 128-bit access mode and 32-bit access mode. The data
type corresponds directly to the single-precision format in the IEEE standard.
gives the precision and range of this data type. Only the fraction part of the significand
is encoded. The integer is assumed to be 1 for all numbers except 0 and denormalized
finite numbers. The exponent of the single-precision data type is encoded in biased
format. The biasing constant is 127 for the single-precision format.
Volume 4: IA-32 SSE Instruction Reference
Results of Operations with NAN Operands
Source Operands
Four Packed FP Data in Memory (at address 1000H)
15 14
13
12
11
(invalid operation exception is masked)
Src1 NaN (converted to QNaN if Src1 is an SNaN).
Src1 NaN (converted to QNaN)
Src1 QNaN
The SNaN converted into a QNaN.
The QNaN source operand.
The SNaN converted into a QNaN/the source QNaN.
The default QNaN real indefinite .
10
8
7
6
9
NaN Result
Byte 0
5
4
3
2
1
0
Memory Address 1000d
Table 4-4
4:481
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