From: lkcl <lkcl@web>
Date: Wed, 14 Sep 2022 12:53:39 +0000 (+0100)
Subject: (no commit message)
X-Git-Tag: opf_rfc_ls005_v1~451
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=9e016ec99320172b4771c0d10f0891bcd23ebb6c;p=libreriscv.git

---

diff --git a/openpower/sv/rfc/ls001.mdwn b/openpower/sv/rfc/ls001.mdwn
index aa70c4319..377cfd3b5 100644
--- a/openpower/sv/rfc/ls001.mdwn
+++ b/openpower/sv/rfc/ls001.mdwn
@@ -212,6 +212,16 @@ The primary options are:
   truncates VL to that exact point. Useful for implementing algorithms
   such as `strcpy` in around 14 high-performance Vector instructions, the
   option exists to include or exclude the failing element.
+* Predicate-result: a strategic mode that effectively turns all and any
+  operations into a type of `cmp`. An `Rc=1 BO test` is performed and if
+  failing the result is **not** written to the regfile. The `Rc=1`
+  Vector of co-results **is** always written (subject to predication).
+  Termed "predicate-result" because the combination of producing then
+  testing a result is as if the test was in a follow-up predicated
+  copy/mv operation, it reduces regfile pressure and instruction count.
+  Also useful on saturated or other overflowing operations, the overflowing
+  elements may be excluded from outputting to the regfile then
+  post-analysed outside of critical hot-loops.
 
 **SVP64Single**