From: lkcl <lkcl@web>
Date: Tue, 8 Dec 2020 17:38:27 +0000 (+0000)
Subject: (no commit message)
X-Git-Tag: convert-csv-opcode-to-binary~1471
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=4df3c70871134d2b233e5a64d984d49777d02803;p=libreriscv.git

---

diff --git a/openpower/sv/av_opcodes.mdwn b/openpower/sv/av_opcodes.mdwn
index d323819d3..bb23d8e13 100644
--- a/openpower/sv/av_opcodes.mdwn
+++ b/openpower/sv/av_opcodes.mdwn
@@ -6,7 +6,21 @@ This page therefore has acompanying discussion at <https://bugs.libre-soc.org/sh
 
 # Audio
 
-TODO
+The fundamental principle for these instructions is:
+
+* identify the scalar primitive
+* assume that longer runs of scalars will have Simple-V vectorisatin applied
+* assume that "swizzle" may be applied at the (vec2 - SUBVL=2) Vector level
+
+Thus for example, where OpenPOWER VSX has vpkswss, this would be achieved in SV with simply:
+
+* addition of a scalar ext/clamp instruction
+* 1st op, swizzle-selection vec2 "select X only" from source to dest:
+  dest.X = extclamp(src.X)
+* 2nd op, swizzle-select vec2 "select Y only" from source to dest
+  dest.Y = extclamp(src.Y)
+
+Macro-op fusion may be used to detect that these two interleave cleanly.
 
 # Video