From 43de92462509b893b01b5e15bcff9246cb12b5bc Mon Sep 17 00:00:00 2001
From: lkcl <lkcl@web>
Date: Sat, 22 Apr 2023 10:53:10 +0100
Subject: [PATCH]

---
 openpower/sv/rfc/ls014.mdwn | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/openpower/sv/rfc/ls014.mdwn b/openpower/sv/rfc/ls014.mdwn
index d1bd4a8b3..7aa9e578c 100644
--- a/openpower/sv/rfc/ls014.mdwn
+++ b/openpower/sv/rfc/ls014.mdwn
@@ -1,10 +1,10 @@
-# RFC ls014
+# RFC ls014 Advanced Scalar Bitmanipulation
 
 **URLs**:
 
 * <https://libre-soc.org/openpower/sv/rfc/ls014/>
 * <https://git.openpower.foundation/isa/PowerISA/issues/TODO>
-* <https://bugs.libre-soc.org/show_bug.cgi?id=1057>
+* <https://bugs.libre-soc.org/show_bug.cgi?id=1065>
 
 **Severity**: Major
 
@@ -29,7 +29,7 @@
 **Summary**
 
 ```
-    Instructions added
+    Instructions added: bmask, grevlut, grevluti
 ```
 
 **Submitter**: Luke Leighton (Libre-SOC)
@@ -52,24 +52,38 @@
 **Keywords**:
 
 ```
-    TODO
+    LUTs, Bitmanipulation, GPR
 ```
 
 **Motivation**
 
-TODO
+Scalar Bitmanipulation in other high-end ISAs have had BMI subsets for over a decade.
+Their use and benefit is well-understood and compiler integration well-established.
+`bmask` brings *twenty four* BMI instructions to the Power ISA.
+
+`grevlut` on the other hand is highly experimental and extremely powerful. Normally
+only `grev` (Generalised Reverse) and occasionally `gor` are added to a Bitmanip-strong
+ISA: grevlut utilises LUTs and inversion to add 512 Generalised Reverse instructions.
+Desirable savings in general binary size are achieved.
 
 **Notes and Observations**:
 
-1. TODO
+1. bmask is a synthesis and generalisation of every "TBM" instruction with additional
+  options not found in any other ISA BMI group.
+2. grevluti as a 32-bit Defined Word is capable of generating over a thousand useful
+   regular-patterned 64-bit "magic constants" that otherwise require either a Load
+   or require several instructions to synthesise
+3. word halfword byte nibble 2-bit 1-bit reversal at multiple levels are all achieved
+   with grevlut. Some of these instructions were explicitly added in Power ISA v3.1
+   but grevlut is akin to xxeval.
+4. grevlut is expensive in hardware (estimated 20,000 gates)
 
 **Changes**
 
 Add the following entries to:
 
 * the Appendices of Book I
-* Book I 3.3.9 Fixed-Point Arithmetic Instructions
-* Book I 4.6.6.1 Floating-Point Elementary Arithmetic Instructions
+* Book I 3.3.9 Fixed-Point Logical Instructions
 * Book I 1.6.1 and 1.6.2
 
 ----------
-- 
2.30.2