Power ISA™ Version 2.03 - Power.org

Version 2.03
Floating Reciprocal Square Root Estimate
[Single]
A-form
[Category: Floating-Point.Phased-In]
frsqrte FRT,FRB (Rc=0)
frsqrte. FRT,FRB (Rc=1)
63 FRT /// FRB /// 26 Rc
0 6 11 16 21 26 31
frsqrtes FRT,FRB (Rc=0)
frsqrtes. FRT,FRB (Rc=1)
59 FRT /// FRB /// 26 Rc
0 6 11 16 21 26 31
A estimate of the reciprocal of the square root of the
floating-point operand in register FRB is placed into
register FRT. The estimate placed into register FRT is
correct to a precision of one part in 32 of the reciprocal
of the square root of (FRB), i.e.,
ABS estimate – 1 ⁄ ( x)
1
(-----------------------------------------------
) ≤ -----
1⁄
( x)
32
where x is the initial value in FRB.
Operation with various special values of the operand is
summarized below.
Operand Result Exception
-∞ QNaN 2 VXSQRT
< 0 QNaN 2 VXSQRT
-0 -∞ 1 ZX
+0 +∞ 1 ZX
+∞ +0 None
SNaN QNaN 2 VXSNAN
QNaN QNaN None
1 No result if FPSCR ZE = 1.
No result if FPSCR VE = 1.
FPSCR FPRF is set to the class and sign of the result,
except for Invalid Operation Exceptions when
FPSCR VE =1 and Zero Divide Exceptions when
FPSCR ZE =1.
The results of executing this instruction may vary
between implementations, and between different executions
on the same implementation.
Special Registers Altered:
FPRF FR (undefined) FI (undefined)
FX ZX XX (undefined)
VXSNAN VXSQRT
CR1
(if Rc=1)
Chapter 4. Floating-Point Processor [Category: Floating-Point]
117