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Vol. 2A 3-335
INSTRUCTION SET REFERENCE, A-M
FIST/FISTP—Store Integer
If the source value is a non-integral value, it is rounded to an integer value, according
to the rounding mode specified by the RC field of the FPU control word.
If the converted value is too large for the destination format, or if the source operand
is an ∞, SNaN, QNAN, or is in an unsupported format, an invalid-arithmetic-operand
condition is signaled. If the invalid-operation exception is not masked, an invalid-
arithmetic-operand exception (#IA) is generated and no value is stored in the desti-
nation operand. If the invalid-operation exception is masked, the integer indefinite
value is stored in memory.
This instruction’s operation is the same in non-64-bit modes and 64-bit mode.
Operation
DEST ← Integer(ST(0));
IF Instruction = FISTP
THEN
PopRegisterStack;
FI;
FPU Flags Affected
C1 Set to 0 if stack underflow occurred.
Indicates rounding direction of if the inexact exception (#P) is
generated: 0
← not roundup; 1 ← roundup.
Set to 0 otherwise.
C0, C2, C3 Undefined.
Floating-Point Exceptions
#IS Stack underflow occurred.
#IA Converted value is too large for the destination format.
Source operand is an SNaN, QNaN, ±∞, or unsupported format.
#P Value cannot be represented exactly in destination format.
NaN
*
NOTES:
F Means finite floating-point value.
IMeans integer.
* Indicates floating-point invalid-operation (#IA) exception.
** 0 or ±1, depending on the rounding mode.
Table 3-32. FIST/FISTP Results (Contd.)
ST(0) DEST