Automatic Application Specific Floating-point Unit Generation

This paper describes the creation of custom floating point units (FPUs) for application specific instruction set processors (ASIPs). ASIPs allow the customization of processors for use in embedded systems by extending the instruction set, which enhances the performance of an application or a class of applications. These extended instructions are manifested as separate hardware blocks, making the creation of any necessary floating point instructions quite unwieldy. On the other hand, using a predefined FPU includes a large monolithic hardware block with considerable number of unused instructions. A customized FPU will overcome these drawbacks, yet the manual creation of one is a time consuming, error prone process. This paper presents a methodology for automatically generating floating-point units (FPUs) that are customized for specific applications at the instruction level. Generated FPUs comply with the IEEE754 standard, which is an advantage over FP format customization. Custom FPUs were generated for several Mediabench applications. Area savings over a fully-featured FPU without resource sharing of 26%-80% without resource sharing and 33%-87% with resource sharing, were obtained. Clock period increased in some cases by up to 9.5% due to resource sharing