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INSTRUCTION SET REFERENCE
FPREM1Partial Remainder
Description
This instruction computes the IEEE remainder obtained from dividing the value in the ST(0)
register (the dividend) by the value in the ST(1) register (the divisor or modulus), and stores the
result in ST(0). The remainder represents the following value:
Remainder = ST(0)
?
(Q
?
ST(1))
Here, Q is an integer value that is obtained by rounding the real-number quotient of [ST(0) /
ST(1)] toward the nearest integer value. The magnitude of the remainder is less than half the
magnitude of the modulus, unless a partial remainder was computed (as described below).
This instruction produces an exact result; the precision (inexact) exception does not occur and
the rounding control has no effect. The following table shows the results obtained when
computing the remainder of various classes of numbers, assuming that underflow does not
occur.
NOTES:
FMeans finite-real number.
*Indicates floating-point invalid-arithmetic-operand (#IA) exception.
**Indicates floating-point zero-divide (#Z) exception.
When the result is 0, its sign is the same as that of the dividend. When the modulus is
?
, the
result is equal to the value in ST(0).
The FPREM1 instruction computes the remainder specified in IEEE Std 754. This instruction
operates differently from the FPREM instruction in the way that it rounds the quotient of ST(0)
divided by ST(1) to an integer (refer to the Operation section below).
Opcode
Instruction
Description
D9 F5
FPREM1
Replace ST(0) with the IEEE remainder obtained from
dividing ST(0) by ST(1)
ST(1)
??
?
F
?
0
+
0
+
F
+
?
NaN
??
*
*
*
*
*
*NaN
ST(0)
?
FST(0)
±
F or
?
0**
**
±
F or
?
0ST(0)NaN
?
0
?
0
?
0
*
*
?
0
?
0NaN
+
0
+0
+0
*
*
+0
+0NaN
+
FST(0)
±
F or +0**
**
±
F or +0ST(0)NaN
+
?
*
*
*
*
*
*NaN
NaNNaNNaNNaNNaNNaNNaNNaN
