ST(0)
DEST
-
or Value Too Large for DEST Format
*
F ≤ −1
-I
-1 < -F < -0
**
-0
0
+0
0
+0 < +F < +1
**
F ≥ +1
+I
+ or Value Too Large for DEST Format
*
NaN
*
Opcode |
Instruction |
Description |
|---|---|---|
|
DF /2 |
FIST m16int |
Store ST(0) in m16int |
|
DB /2 |
FIST m32int |
Store ST(0) in m32int |
|
DF /3 |
FISTP m16int |
Store ST(0) in m16int and pop register stack |
|
DB /3 |
FISTP m32int |
Store ST(0) in m32int and pop register stack |
|
DF /7 |
FISTP m64int |
Store ST(0) in m64int and pop register stack |
The FIST instruction converts the value in the ST(0) register to a signed integer and stores the result in the destination operand. Values can be stored in word- or short-integer format. The destination operand specifies the address where the first byte of the destination value is to be stored.
The FISTP instruction performs the same operation as the FIST instruction and then pops the register stack. To pop the register stack, the processor marks the ST(0) register as empty and increments the stack pointer (TOP) by 1. The FISTP instruction can also stores values in long-integer format.
The following table shows the results obtained when storing various classes of numbers in integer format.
ST(0) |
DEST |
|---|---|
|
- |
* |
|
F ≤ −1 |
-I |
|
-1 < -F < -0 |
** |
|
-0 |
0 |
|
+0 |
0 |
|
+0 < +F < +1 |
** |
|
F ≥ +1 |
+I |
|
+ |
* |
|
NaN |
* |
Note F Means finite-real number. I Means integer.
* Indicates floating-point invalid-operation (#IA) exception.
** 0 or ±1, depending on the rounding mode.
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 value being stored is too large for the destination format, is
an , is a NaN, or
is in an unsupported format and if the invalid-arithmetic-operand exception
(#IA) is unmasked, an invalid-operation exception is generated and no
value is stored in the destination operand. If the invalid-operation exception
is masked, the integer indefinite value is stored in the destination operand.
DEST 
Integer(ST(0));
IF instruction FISTP
THEN
PopRegisterStack;
FI;
C1--Set to 0 if stack underflow occurred. Indicates rounding direction
of if the inexact exception (#P) is generated: 0 not roundup; 1 roundup. Cleared to 0 otherwise.
C0, C2, C3 - Undefined.
#IS - Stack underflow occurred.
#IA - Source operand is too large for the destination format Source operand is a NaN value or unsupported format.
#P - Value cannot be represented exactly in destination format.
#GP(0) - If the destination is located in a non-writable segment. If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit. If the DS, ES, FS, or GS register is used to access memory and it contains a null segment selector.
#SS(0) - If a memory operand effective address is outside the SS segment limit.
#NM - EM or TS in CR0 is set.
#PF(fault-code) - If a page fault occurs.
#AC(0) - If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3.
#GP - If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.
#SS - If a memory operand effective address is outside the SS segment limit.
#NM - EM or TS in CR0 is set.
#GP(0) - If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.
#SS(0) - If a memory operand effective address is outside the SS segment limit.
#NM - EM or TS in CR0 is set.
#PF(fault-code) - If a page fault occurs.
#AC(0) - If alignment checking is enabled and an unaligned memory reference is made.
For details, see Volume 2A and Volume 2B of the Intel(R) 64 and IA-32 Intel Architecture Software Developer's Manual. For the latest updates on the instruction set information, go to the web site.