From: lkcl <lkcl@web>
Date: Fri, 27 May 2022 10:16:12 +0000 (+0100)
Subject: (no commit message)
X-Git-Tag: opf_rfc_ls005_v1~2063
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=bb4c024eced053b0fe3914a62406535478a5f480;p=libreriscv.git

---

diff --git a/openpower/sv/svp64_quirks.mdwn b/openpower/sv/svp64_quirks.mdwn
index ad3662fe6..72458c425 100644
--- a/openpower/sv/svp64_quirks.mdwn
+++ b/openpower/sv/svp64_quirks.mdwn
@@ -78,4 +78,15 @@ this section.
 
 # Branch-Conditional
 
-[[sv/branches]]
+[[sv/branches]] are a very special exception to the rule that the
+Scalar instruction shall not be modified.  This because of the tight
+integration with looping and the application of Boolean Logic
+manipulation needed for Parallel operations (predicate mask usage).
+
+One key difference is that LR is only updated if certain additional
+conditions are met, whereas Scalar `bclrl` for example unconditionally
+overwrites LR.
+
+Well over 500 Vectorised branch instructions exist in SVP64 due to the
+number of options available: close integration and interaction with
+the base Scalar Branch was unavoidable.