Fabs-absolute value, Fabs—absolute value – Intel 253666-024US User Manual
Page 334
3-288 Vol. 2A
FABS—Absolute Value
INSTRUCTION SET REFERENCE, A-M
FABS—Absolute Value
Description
Clears the sign bit of ST(0) to create the absolute value of the operand. The following
table shows the results obtained when creating the absolute value of various classes
of numbers.
This instruction’s operation is the same in non-64-bit modes and 64-bit mode.
Operation
ST(0) ← |ST(0)|;
FPU Flags Affected
C1
Set to 0 if stack underflow occurred; otherwise, set to 0.
C0, C2, C3
Undefined.
Floating-Point Exceptions
#IS
Stack underflow occurred.
Protected Mode Exceptions
#NM
CR0.EM[bit 2] or CR0.TS[bit 3] = 1.
#UD
If the LOCK prefix is used.
Opcode
Instruction
64-Bit
Mode
Compat/
Leg Mode
Description
D9 E1
FABS
Valid
Valid
Replace ST with its absolute value.
Table 3-22. Results Obtained from FABS
ST(0) SRC
ST(0) DEST
−
•
+
•
−F
+F
−0
+0
+0
+0
+F
+F
+
∞
+
•
NaN
NaN
NOTES:
F Means finite floating-point value.