From: Andrey Miroshnikov <andrey@technepisteme.xyz>
Date: Thu, 9 Nov 2023 23:32:38 +0000 (+0000)
Subject: Added a bit of explanation for the three instructions
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=f36dcf74ead4da26825747b5e1cd4280653e72e6;p=libreriscv.git

Added a bit of explanation for the three instructions
---

diff --git a/openpower/sv/cookbook/remap_matrix.mdwn b/openpower/sv/cookbook/remap_matrix.mdwn
index 973444f7a..8eefea51e 100644
--- a/openpower/sv/cookbook/remap_matrix.mdwn
+++ b/openpower/sv/cookbook/remap_matrix.mdwn
@@ -210,6 +210,24 @@ ISACaller)*
     sv.maddld *0, *16, *32, *0
 ```
 
+As you can see, only three instructions are required to perform arbitrary
+matrix multiplication, with non-power-of-2 matrices!
+
+The reason why the main part of matrix multiplication is so simple is down
+to three reasons:
+
+- RISC ISA with powerful and simple instructions (Power ISA SFS/SFFS)
+- REMAP indexing system - generates index schedules for a range of
+  problems: matrix multiply, FFT, DCT, programmer-defined, etc.
+- Simple-V SVP64 looping system based on instruction prefixing which turns
+  any scalar instruction into a vector one. Can follow consecutive element
+  indexing, or REMAP schedule indexing.
+
+Additionally, if instead of matrix multiplication, a different operation is
+required (say, to perform logical operations on rows/cols), the third
+instruction - `maddld` - can be substituted for a different operation. This is
+beyond the scope of this guide however.
+
 ## svshape
 
 The `svshape` instruction is a convenient way to access the `SVSHAPE` Special
@@ -220,7 +238,8 @@ would be possible.
 
 The REMAP system has 16 modes, all of which are accessible through the
 `svshape` instruction. However for the purpose of this guide, only SVrm=0
-(Matrix Multiply) will be covered.
+(Matrix Multiply) will be covered. The Matrix Multiply mode can be used to
+produce indices in the form of the inner product table shown above.
 
 ### SVSHAPE Remapping SPRs