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Latest commit 2fe9a12 Jan 28, 2019

README.md

Berkeley Hardware Floating-Point Units

This repository contains hardware floating-point units written in Chisel. This library contains parameterized floating-point units for fused multiply-add operations, conversions between integer and floating-point numbers, and conversions between floating-point conversions with different precision.

WARNING: These units are works in progress. They may not be yet completely free of bugs, nor are they fully optimized.

Recoded Format

The floating-point units in this repository work on an internal recoded format (exponent has an additional bit) to handle subnormal numbers more efficiently in a microprocessor. A more detailed explanation will come soon, but in the mean time here are some example mappings for single-precision numbers.

IEEE format                           Recoded format
----------------------------------    -----------------------------------
s 00000000 00000000000000000000000    s 000------ 00000000000000000000000
s 00000000 00000000000000000000001    s 001101011 00000000000000000000000
s 00000000 0000000000000000000001f    s 001101100 f0000000000000000000000
s 00000000 000000000000000000001ff    s 001101101 ff000000000000000000000
    ...              ...                   ...              ... 
s 00000000 001ffffffffffffffffffff    s 001111111 ffffffffffffffffffff000
s 00000000 01fffffffffffffffffffff    s 010000000 fffffffffffffffffffff00
s 00000000 1ffffffffffffffffffffff    s 010000001 ffffffffffffffffffffff0
s 00000001 fffffffffffffffffffffff    s 010000010 fffffffffffffffffffffff
s 00000010 fffffffffffffffffffffff    s 010000011 fffffffffffffffffffffff
    ...              ...                   ...              ... 
s 11111101 fffffffffffffffffffffff    s 101111110 fffffffffffffffffffffff
s 11111110 fffffffffffffffffffffff    s 101111111 fffffffffffffffffffffff
s 11111111 00000000000000000000000    s 110------ -----------------------
s 11111111 fffffffffffffffffffffff    s 111------ fffffffffffffffffffffff

Unit-Testing

To unit-test these floating-point units, you need the berkeley-testfloat-3 package.

To test floating-point units with the C simulator:

$ make