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X-Hacker.org- iAPx86 - <b>ftst test for zero exceptions: i d</b>
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FTST Test for zero Exceptions: I D
C3 C2 C1 C0: * * * *
FTST
Logic CMP ST, 0.0
set condition codes
FTST compares the stack top to 0.0. Following the instruction, the
condition codes reflect the relationship between ST and 0.0.
C3 C0
0 0 ST > 0.0
0 1 ST < 0.0
1 0 ST = +- 0.0
1 1 ST is not comparable
Note
If ST contains a NaN or has an undefined format, or a stack fault
occurs, the invalid-operation exception is raised and the condition
bits are set to 'unordered'.
The sign of zero is ignored, so that -0.0 = +0.0.
Opcode Format
D9 E4 FTST
Timing
Operand 8087 287 387 486 Pentium
- 38-48 38-48 28 4 4/1 FX
See Also: FCOM FICOM CC
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