From: lkcl <lkcl@web>
Date: Sat, 2 Apr 2022 12:05:40 +0000 (+0100)
Subject: (no commit message)
X-Git-Tag: opf_rfc_ls005_v1~2930
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=4cd0342ba4372a4e426c656590acde06eb39a1bd;p=libreriscv.git

---

diff --git a/openpower/sv/branches.mdwn b/openpower/sv/branches.mdwn
index aa8d79343..fe16696c6 100644
--- a/openpower/sv/branches.mdwn
+++ b/openpower/sv/branches.mdwn
@@ -189,6 +189,15 @@ LRu and CTR-test modes are where SVP64 Branches subtly differ from
 Scalar v3.0B Branches. `bclr` for example will always update LR, whereas
 `sv.bclr/lru` will only update LR if the branch succeeds.
 
+Of special interest is that when using ALL Mode (Great Big AND
+of all Condition Tests), if `VL=0`,
+which is rare but can occur in Data-Dependent Modes, the Branch
+will always take place because there will be no failing Condition
+Tests to prevent it. Likewise when not using ALL Mode (Great Big OR
+of all Condition Tests) and `VL=0` the Branch is guaranteed not
+to occur because there will be no *successful* Condition Tests
+to make it happen.
+
 # Vectorised CR Field numbering, and Scalar behaviour
 
 It is important to keep in mind that just like all SVP64 instructions,