Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 1401

FABS—Absolute Value
Opcode
D9 E1
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.
ST(0) SRC
 •
 F
 0
 0
+F
+ 
NaN
Note:
Fmeans finite-real number.
Operation
ST(0)  |ST(0)|
FPU Flags Affected
C1
C0, C2, C3
Additional Itanium System Environment Exceptions
Itanium Reg Faults Disabled FP Register Fault if PSR.dfl is 1, NaT Register Consumption
Floating-point Exceptions
#IS
Protected Mode Exceptions
#NM
Real Address Mode Exceptions
#NM
Virtual 8086 Mode Exceptions
#NM
Volume 4: Base IA-32 Instruction Reference
Instruction Description
FABS Replace ST with its absolute value.
ST(0) DEST
+ 
+F
+0
+0
+F
+ 
NaN
Set to 0 if stack underflow occurred; otherwise, cleared to 0.
Undefined.
Abort.
Stack underflow occurred.
EM or TS in CR0 is set.
EM or TS in CR0 is set.
EM or TS in CR0 is set.
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