Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 1323

AAA—ASCII Adjust After Addition
Opcode
37
Description
Adjusts the sum of two unpacked BCD values to create an unpacked BCD result. The AL
register is the implied source and destination operand for this instruction. The AAA
instruction is only useful when it follows an ADD instruction that adds (binary addition)
two unpacked BCD values and stores a byte result in the AL register. The AAA
instruction then adjusts the contents of the AL register to contain the correct 1-digit
unpacked BCD result.
If the addition produces a decimal carry, the AH register is incremented by 1, and the
CF and AF flags are set. If there was no decimal carry, the CF and AF flags are cleared
and the AH register is unchanged. In either case, bits 4 through 7 of the AL register are
cleared to 0.
Operation
IF ((AL AND FH) > 9) OR (AF = 1)
THEN
AL  (AL + 6);
AH  AH + 1;
AF  1;
CF  1;
ELSE
AF  0;
CF  0;
FI;
AL  AL AND FH;
Flags Affected
The AF and CF flags are set to 1 if the adjustment results in a decimal carry; otherwise
they are cleared to 0. The OF, SF, ZF, and PF flags are undefined.
Additional Itanium System Environment Exceptions
Itanium Reg Faults NaT Register Consumption Abort.
Exceptions (All Operating Modes)
None.
Volume 4: Base IA-32 Instruction Reference
Instruction
AAA
Description
ASCII adjust AL after addition
4:21