From: Andrey Miroshnikov <andrey@technepisteme.xyz>
Date: Mon, 6 Nov 2023 19:26:01 +0000 (+0000)
Subject: Added section on remapyield
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=4be5bec8309348e84bfd3c35df0aebc1a82c5ac7;p=libreriscv.git

Added section on remapyield
---

diff --git a/openpower/sv/cookbook/remap_matrix.mdwn b/openpower/sv/cookbook/remap_matrix.mdwn
index 14df32fe3..4f0757a63 100644
--- a/openpower/sv/cookbook/remap_matrix.mdwn
+++ b/openpower/sv/cookbook/remap_matrix.mdwn
@@ -399,5 +399,47 @@ Screenshots:
 
 [[!img mat_mul_sim_results.png size="600x" ]]
 
+### Remapyield showing how the matrix indices are generated
+
+*(more work required not critically important right now)*
+
+This table was drawn up using the `remapyield.py` code found
+[here](https://git.libre-soc.org/?p=openpower-isa.git;a=blob;f=src/openpower/decoder/isa/remapyield.py;h=d7b4bdeff2ae5d5f319ae036e4dff70de194dc67;hb=HEAD).
+
+The xdim, ydim, and zdim were set to match the values specified in the svshape
+instruction for the above matrix multiply example.
+
+`x`, 'y`, and `z` are iterators for the three loops, with a range between 0 and
+`SVxd-1`, `SVyd-1`, `SVzd-1` respectively.
+
+For the above `svshape` instruction example:
+
+- `x` takes values between 0 and 1 (`SVxd=2`)
+- `y` takes values between 0 and 1 (`SVyd=2`)
+- `z` takes values between 0 and 2 (`SVzd=3`)
+- `x_end`, `y_end`, and `z_end` correspond to the largest permitted values for
+`x`, `y`, and `z` (1, 1, and 2 respectively).
+
+                      | (x ==   | (y ==   | (z ==
+    index | x | y | z |  x_end) |  y_end) |  z_end)
+       0  | 0 | 0 | 0 |    F    |    F    |   F
+       1  | 1 | 0 | 0 |    T    |    F    |   F
+       2  | 0 | 1 | 0 |    F    |    T    |   F
+       3  | 1 | 1 | 0 |    T    |    T    |   F
+       4  | 0 | 0 | 1 |    F    |    F    |   F
+       5  | 1 | 0 | 1 |    T    |    F    |   F
+       6  | 0 | 1 | 1 |    F    |    T    |   F
+       7  | 1 | 1 | 1 |    T    |    T    |   F
+       8  | 0 | 0 | 2 |    F    |    F    |   T
+       9  | 1 | 0 | 2 |    T    |    F    |   T
+      10  | 0 | 1 | 2 |    F    |    T    |   T
+      11  | 1 | 1 | 2 |    T    |    T    |   T
+
+If the `x`, `y`, and `z` sequences are compared with the inner product index
+table, there are some resemblances. Swapping the `x` and `y` (permute=0b10)
+shows that matrix X indices correspond to `y`, matrix Y indices correspond to
+`x` (if the following equation used: `x+z*z_end`), and matrix Z indices
+correspond to `z`.
+
 [[!tag svp64_cookbook ]]