This document describes the matrix extension for RISC-V.
Matrix extension implement matrix multiplications by partitioning the input and output matrix into tiles, which are then stored to matrix registers.
Tile size usually refers to the dimensions of these tiles. For the operation C = AB in figure below, the tile size of C is mtilem × mtilen, the tile size of A is mtilem × mtilek and the tile size of B is mtilek × mtilen.
Each matrix multiplication instruction computes its output tile by stepping through the K dimension in tiles, loading the required values from the A and B matrices, and multiplying and accumulating them into the output.
Matrix extension is strongly inspired by the RISC-V Vector "V" extension.