Filter
Top Products
Release 1.0, 1 July 2002 F. Chapter B IEEE Std 754-1985 Requirements for SPARC V9 65
Pessimistic Overflow
If a condition in
TABLE B-4
is true, SPARC64 V regards the operation as having an
overflow condition.
B.6.2 Operation Under FSR.NS = 1
When FSR.NS = 1 (nonstandard mode), SPARC64 V zeroes all the input
denormalized operands before the operation and signals an inexact exception if
enabled. If the operation generates a denormalized result, SPARC64 V zeroes the
result and also signals an inexact exception if enabled. The following list defines the
operation in detail.
■
If either operand is a denormalized number and both operands are non-zero, non-
NaN, and non-infinity numbers, the input denormalized operand is replaced with
a zero with same sign, and the operation is performed. If enabled, inexact
exception is signalled; an
fp_exception_ieee_754
(tt = 021
16
) is generated, with
nxc=1 in FSR.cexc (FSR.ftt=01
16
;
IEEE754_exception
). However, if the
operation is FDIV(s,d) and either a
division_by_zero
or an
invalid_operation
condition is detected, or if the operation is FSQRT(s,d) and an
invalid_operation
condition is detected, the inexact condition is not reported.
■
If the result before rounding is a denormalized number, the result is flushed to a
zero with a same sign and signals either an underflow exception or an inexact
exception, depending on FSR.TEM.
As observed from the preceding, when FSR.NS = 1, SPARC64 V generates neither
an
unfinished_FPop
exception nor a denormalized number as a result.
TABLE B-5
TABLE B-3
Conditions for a Pessimistic Zero
Operations
Conditions
One operand is denormalized
1
1. Both operands are non-zero, non-NaN, and non-infinity numbers.
Both are denormalized Both are normal fp-number
2
2. Both may be zero, but both are non-NaN and non-infinity numbers.
FdTOs always — eres ≤ -25
FMULs,
FMULd
single precision: Er ≤−25
double precision: Er ≤−54
Always single precision: eres ≤−25
double precision: eres ≤−54
FDIVs,
FDIVd
single precision: Er ≤−25
double precision: Er ≤−54
Never single precision: eres ≤−25
double precision: eres ≤−54
TABLE B-4
Pessimistic Overflow Conditions
Operations Conditions
FDIVs The divisor (operand2; rs2) is a denormalized number and, Er ≥ 255.
FDIVd The divisor (operand2; rs2) is a denormalized number and, E ≥ 2047.