Based on the code from https://github.com/riscv/riscv-go/ originally
written by Amol Bhave.

Change-Id: I8d5377096d4ff8b198dadb630511f9a0347f9797
Reviewed-on: https://go-review.googlesource.com/107339
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>