IEEE754 Floating-Point ALU, in nmigen

This project implements a pipelined IEEE754 floating-point ALU that supports FP16, FP32 and FP64. It is a general-purpose unit that may be used in any project (not limited to one specific processor).

Developed under a Grant from NLnet (http://nlnet.nl), more information may be found at http://libre-soc.org

Requirements

• nmigen
• libresoc-nmutil
• yosys (latest git repository, required by nmigen)
• sfpy (running unit tests). provides python bindings to berkeley softfloat-3

Building sfpy

The standard sfpy will not work without being modified to the type of IEEE754 FP emulation being tested. This FPU is emulating RISC-V, and there is some weirdness in x86 IEEE754 implementations when it comes to FP16 non-canonical NaNs.

The following modifications are required to the sfpy berkeley-softfloat-3 submodule:

cd /path/to/sfpy/berkeley-softfloat-3
git apply /path/to/ieee754fpu/berkeley-softfloat.patch

The following modifications are required to the sfpy SoftPosit Makefile:

cd /path/to/sfpy/SoftPosit
git apply /path/to/ieee754fpu/SoftPosit.patch

Useful resources

• https://en.wikipedia.org/wiki/IEEE_754-1985
• http://weitz.de/ieee/
• https://steve.hollasch.net/cgindex/coding/ieeefloat.html