ISA Specifications Volume I: RISC-V Unprivileged ISA Specification Preamble Preamble This document is a derivative of “The RISC-V Instruction Set Manual, Volume I: User-Level ISA Version 2.1” released under the following license: ©2010-2017 Andrew Waterman, Yunsup Lee, David Patterson, Krste Asanović. Creative Commons Attribution 4.0 International License. Please cite as: “The RISC-V Instruction Set Manual, Volume I: User-Level ISA, Document Version 20191214-draft”, Editors Andrew Waterman and Krste Asanović, RISC-V Foundation, December 2019. This document is released under a Creative Commons Attribution 4.0 International License. Contributors Contributors to all versions of the spec in alphabetical order (please contact editors to suggest corrections): Arvind, Krste Asanović, Derek Atkins, Rimas Avižienis, Jacob Bachmeyer, Christopher F. Batten, Allen J. Baum, Scott Beamer, Abel Bernabeu, Hans Boehm, Alex Bradbury, Preston Briggs, Christopher Celio, Chuanhua Chang, David Chisnall, Paul Clayton, Palmer Dabbelt, L Peter Deutsch, Ken Dockser, Paul Donahue, Aaron Durbin, Roger Espasa, Greg Favor, Shaked Flur, Stefan Freudenberger, Marc Gauthier, Andy Glew, Jan Gray, Gianluca Guida, Michael Hamburg, John Hauser, Christian Herber, David Horner, Bruce Hoult, Bill Huffman, John Ingalls, Alexandre Joannou, Olof Johansson, Ben Keller, David Kruckemyer, Tariq Kurd, Yunsup Lee, Paul Loewenstein, Daniel Lustig, Yatin Manerkar, Luc Maranget, Ben Marshall, Margaret Martonosi, Phil McCoy, Nathan Menhorn, Christoph Müllner, Joseph Myers, Vijayanand Nagarajan, Torbjørn Viem Ness, Rishiyur Nikhil, Jonas Oberhauser, Stefan O’Rear, Markku-Juhani O. Saarinen, Albert Ou, John Ousterhout, Daniel Page, David Patterson, Christopher Pulte, Jose Renau, Susmit Sarkar, Josh Scheid, Colin Schmidt, Peter Sewell, Ved Shanbhogue, Brent Spinney, Brendan Sweeney, Michael Taylor, Wesley Terpstra, Matt Thomas, Tommy Thorn, Philipp Tomsich, Caroline Trippel, Ray VanDeWalker, Muralidaran Vijayaraghavan, Megan Wachs, Paul Wamsley, Andrew Waterman, Robert Watson, David Weaver, Derek Williams, Claire Wolf, Andrew Wright, Reinoud Zandijk, and Sizhuo Zhang. Please contact RISC-V International to suggest corrections. Title Page Preface