From: lkcl <lkcl@web>
Date: Sat, 29 Apr 2023 12:27:07 +0000 (+0100)
Subject: remove Rc=1 variants from twin butterfly instructions
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=58319b41de4c69a9d68a449612ade518e5548c34;p=libreriscv.git

remove Rc=1 variants from twin butterfly instructions
---

diff --git a/openpower/sv/twin_butterfly.mdwn b/openpower/sv/twin_butterfly.mdwn
index 5862253df..f6d3882eb 100644
--- a/openpower/sv/twin_butterfly.mdwn
+++ b/openpower/sv/twin_butterfly.mdwn
@@ -9,7 +9,7 @@
 * [[openpower/isa/svfixedarith]]
 <!-- show -->
 
-# Twin Butterfly Integer DCT Instruction(s)
+# Rationale for Twin Butterfly Integer DCT Instruction(s)
 
 The goal is to implement instructions that calculate the expression:
 
@@ -39,11 +39,13 @@ The instruction will run in accumulate mode, so in order to calculate the 2-coef
 
 ## Integer Butterfly Multiply Add/Sub FFT/DCT
 
+**Add the following to Book I Section 3.3.9.1**
+
 A-Form
 
 ```
     |0     |6     |11      |16     |21      |26    |31 |
-    | PO   |  RT  |   RA   |   RB  |   SH   |   XO |Rc |
+    | PO   |  RT  |   RA   |   RB  |   SH   |   XO |/  |
 
 ```
 
@@ -80,15 +82,16 @@ Special Registers Altered:
 
 ## Floating Twin Multiply-Add DCT [Single]
 
+**Add the following to Book I Section 4.6.6.3 **
+
 X-Form
 
 ```
     |0     |6     |11      |16     |21      |31 |
-    | PO   |  FRT |  FRA   |  FRB  |   XO   | Rc|
+    | PO   |  FRT |  FRA   |  FRB  |   XO   |/  |
 ```
 
 * fdmadds FRT,FRA,FRB (Rc=0)
-* fdmadds. FRT,FRA,FRB (Rc=1)
 
 Pseudo-code:
 
@@ -104,20 +107,20 @@ Special Registers Altered:
     FPRF FR FI
     FX OX UX XX
     VXSNAN VXISI VXIMZ
-    CR1          (if Rc=1)
 ```
 
 ## Floating Multiply-Add FFT [Single]
 
+**Add the following to Book I Section 4.6.6.3 **
+
 X-Form
 
 ```
     |0     |6     |11      |16     |21      |31 |
-    | PO   |  FRT |  FRA   |  FRB  |   XO   | Rc|
+    | PO   |  FRT |  FRA   |  FRB  |   XO   |/  |
 ```
 
 * ffmadds FRT,FRA,FRB (Rc=0)
-* ffmadds. FRT,FRA,FRB (Rc=1)
 
 Pseudo-code:
 
@@ -132,5 +135,4 @@ Special Registers Altered:
     FPRF FR FI
     FX OX UX XX
     VXSNAN VXISI VXIMZ
-    CR1          (if Rc=1)
 ```