image/svg+xml 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 C1Set to 0. C0, C2, C3 Undefined. Floating-Point Exceptions #ISStack underflow occurred. Protected Mode Exceptions #NMCR0.EM[bit 2] or CR0.TS[bit 3] = 1. #UD If the LOCK prefix is used. Real-Address Mode Exceptions Same exceptions as in protected mode. Virtual-8086 Mode Exceptions Same exceptions as in protected mode. Compatibility Mode Exceptions Same exceptions as in protected mode. 64-Bit Mode Exceptions Same exceptions as in protected mode. OpcodeInstruction64-Bit Mode Compat/ Leg Mode Description D9 E1FABSValidValidReplace ST with its absolute value. Table 3-17. Results Obtained from FABS ST(0) SRCST(0) DEST − ∞ + ∞ − F + F − 0 + 0 + 0 + 0 + F + F + ∞ + ∞ NaNNaN NOTES: FMeans finite floating-point value. This UNOFFICIAL reference was generated from the official Intel® 64 and IA-32 Architectures Software Developer’s Manual by a dumb script. There is no guarantee that some parts aren't mangled or broken and is distributed WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE .