Power ISA™ Version 2.03 - Power.org

Version 2.03
Vector Reciprocal Estimate
Single-Precision
VX-form
Vector Reciprocal Square Root Estimate
Single-Precision
VX-form
vrefp
VRT,VRB
vrsqrtefp
VRT,VRB
4 VRT /// VRB 266
0 6 11 16 21 31
do i=0 to 127 by 32
VRT i:i+31 ReciprocalEstimateSP( (VRB) i:i+31 )
For each vector element i from 0 to 3, do the following.
The single-precision floating-point estimate of the
reciprocal of single-precision floating-point element
i in VRB is placed into word element i of
VRT.
Unless the single-precision floating-point result of computing
the reciprocal of a value would be a zero, an
infinity, or a QNaN, the estimate has a relative error in
precision no greater than one part in 4096.
Note that results may vary between implementations,
and between different executions on the same implementation.
The result for various special cases of the source value
is given below.
Value
Result
- Infinity -0
- 0 - Infinity
+0 + Infinity
+Infinity +0
NaN
QNaN
Special Registers Altered:
None
4 VRT /// VRB 330
0 6 11 16 21 31
do i=0 to 127 by 32
VRT i:i+31 ReciprocalSquareRootEstimateSP(
(VRB) i:i+31 )
For each vector element i from 0 to 3, do the following.
The single-precision floating-point estimate of the
reciprocal of the square root of single-precision
floating-point element i in VRB is placed into word
element i of VRT.
Let x be any single-precision floating-point value.
Unless the single-precision floating-point result of computing
the reciprocal of the square root of x would be a
zero, an infinity, or a QNaN, the estimate has a relative
error in precision no greater than one part in 4096.
Note that results may vary between implementations,
and between different executions on the same implementation.
The result for various special cases of the source value
is given below.
Value
Result
- Infinity QNaN
< 0 QNaN
- 0 - Infinity
+0 + Infinity
+Infinity +0
NaN
QNaN
Special Registers Altered:
None
192
Power ISA -- Book I