Enhanced Floating-Point Multiply-Add with Full Denormal Support

• Published in: 2023 IEEE 30th Symposium on Computer Arithmetic (ARITH) pp. 143 - 150
• Main Authors: Sohn, Jongwook, Dean, David K., Quintana, Eric, Wong, Wing Shek
• Format: Conference Proceeding
• Language: English
• Published: IEEE 04.09.2023
• Subjects: Delays; Digital arithmetic; Encoding; floating-point arithmetic; floating-point denormal numbers; Floating-point multiply-add; high-speed computer arithmetic; Logic arrays; Next generation networking; Optimization
• ISSN: 2576-2265
• DOI: 10.1109/ARITH58626.2023.00015

This paper presents an enhanced floating-point multiply-add (FMA) design for the Intel E-Core processor. FMA is one of the most widely used operation in many applications. The proposed FMA is executed in 4 cycles, fully pipelined, handles SSE/AVX operations for scalar/packed IEEE single and double precision, and supports all four rounding modes. Also, the proposed FMA fully supports both denormal inputs and underflow outputs without microcode assistance. To achieve the 4-cycle FMA with full denormal support, several optimization techniques are applied: one-way alignment, radix-16 Booth encoding for the multiplier, merged J-bit correction and aligned significand with the multiply array, modified leading zero anticipation (LZA) for masking the underflow, parallel sticky and all-ones detection with the normalization, and merged two's complement with the rounding logic. As a result, the proposed FMA achieved not only full denormal support but also about 10 - 30% reduced area and about 10 - 20% reduced latency compared to the traditional FMAs.