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3-338 Vol. 2A FISTTP—Store Integer with Truncation
INSTRUCTION SET REFERENCE, A-M
FISTTP—Store Integer with Truncation
Description
FISTTP converts the value in ST into a signed integer using truncation (chop) as
rounding mode, transfers the result to the destination, and pop ST. FISTTP accepts
word, short integer, and long integer destinations.
The following table shows the results obtained when storing various classes of
numbers in integer format.
This instruction’s operation is the same in non-64-bit modes and 64-bit mode.
Operation
DEST ← ST;
pop ST;
Flags Affected
C1 is cleared; C0, C2, C3 undefined.
Opcode Instruction 64-Bit Mode Compat/
Leg Mode
Description
DF /1 FISTTP m16int Valid Valid Store ST(0) in m16int with
truncation.
DB /1 FISTTP m32int Valid Valid Store ST(0) in m32int with
truncation.
DD /1 FISTTP m64int Valid Valid Store ST(0) in m64int with
truncation.
Table 3-33. FISTTP Results
ST(0) DEST
−∞ or Value Too Large for DEST Format *
F ≤ − 1
− I
− 1<F < + 1 0
F
≥ +1 + I
+
∞ or Value Too Large for DEST Format *
NaN *
NOTES:
F Means finite floating-point value.
Ι Means integer.
∗ Indicates floating-point invalid-operation (#IA) exception.