A Decimal Floating-Point Adder with Decoded Operands and a Decimal Leading-Zero Anticipator

The IEEE 754-2008 Standard for Floating-Point Arithmetic was officially approved this year. One of the most important revisions to IEEE 754-1985 is the introduction of decimal floating-point (DFP) formats and operations. Since IEEE 754-1985 was revised, major microprocessor vendors have been working on hardware designs and software libraries for decimal arithmetic. Because the new standard has been approved, many software vendors are planning to adapt the new decimal formats into their applications. Therefore, it is important to investigate efficient algorithms and hardware designs for common DFP arithmetic operations to improve the performance of these applications. This paper presents a novel DFP adder with decoded operands and a decimal leading-zero anticipator (LZA). The DFP adder is based on a previous DFP adder design with several new features, including a new internal format, an improved operand pre-correction stage, and a novel decimal LZA to obtain better timing for decimal addition and subtraction. Synthesis results show that the new DFP adder is roughly 14% faster than the previous design.