From ada402d12038ecfe920ed2d39519ca123f06b693 Mon Sep 17 00:00:00 2001
From: lkcl <lkcl@web>
Date: Sat, 29 Apr 2023 13:22:53 +0100
Subject: [PATCH]

---
 openpower/sv/twin_butterfly.mdwn | 34 +++++++++++---------------------
 1 file changed, 12 insertions(+), 22 deletions(-)

diff --git a/openpower/sv/twin_butterfly.mdwn b/openpower/sv/twin_butterfly.mdwn
index 3bd36d897..5862253df 100644
--- a/openpower/sv/twin_butterfly.mdwn
+++ b/openpower/sv/twin_butterfly.mdwn
@@ -14,13 +14,13 @@
 The goal is to implement instructions that calculate the expression:
 
 ```
-fdct_round_shift((a +/- b) * c)
+    fdct_round_shift((a +/- b) * c)
 ```
 
 For the single-coefficient butterfly instruction, and:
 
 ```
- fdct_round_shift(a * c1  +/- b * c2)
+    fdct_round_shift(a * c1  +/- b * c2)
 ```
 
 For the double-coefficient butterfly instruction.
@@ -28,7 +28,7 @@ For the double-coefficient butterfly instruction.
 `fdct_round_shift` is defined as `ROUND_POWER_OF_TWO(x, 14)`
 
 ```
-#define ROUND_POWER_OF_TWO(value, n) (((value) + (1 << ((n)-1))) >> (n))
+    #define ROUND_POWER_OF_TWO(value, n) (((value) + (1 << ((n)-1))) >> (n))
 ```
 
 These instructions are at the core of **ALL** FDCT calculations in many major video codecs, including -but not limited to- VP8/VP9, AV1, etc.
@@ -37,10 +37,16 @@ Arm includes special instructions to optimize these operations, although they ar
 The suggestion is to have a single instruction to calculate both values `((a + b) * c) >> N`, and `((a - b) * c) >> N`.
 The instruction will run in accumulate mode, so in order to calculate the 2-coeff version one would just have to call the same instruction with different order a, b and a different constant c.
 
-## [DRAFT] Integer Butterfly Multiply Add/Sub FFT/DCT
+## Integer Butterfly Multiply Add/Sub FFT/DCT
 
 A-Form
 
+```
+    |0     |6     |11      |16     |21      |26    |31 |
+    | PO   |  RT  |   RA   |   RB  |   SH   |   XO |Rc |
+
+```
+
 * maddsubrs  RT,RA,SH,RB
 
 Pseudo-code:
@@ -70,25 +76,9 @@ Special Registers Altered:
     None
 ```
 
-Where we have added this variant in A-Form (defined in fields.txt):
-
-```
-# # 1.6.17 A-FORM
-    |0     |6     |11      |16     |21      |26    |31 |
-    | PO   |  RT  |   RA   |   RB  |   SH   |   XO |Rc |
-
-```
-
-The instruction has been added to `minor_22.csv`:
-
-```
-------01000,ALU,OP_MADDSUBRS,RT,CONST_SH,RB,RT,NONE,CR0,0,0,ZERO,0,NONE,0,0,0,0,1,0,RC_ONLY,0,0,maddsubrs,A,,1,unofficial until submitted and approved/renumbered by the opf isa wg
-```
-
-
 # Twin Butterfly Integer DCT Instruction(s)
 
-## [DRAFT] Floating Twin Multiply-Add DCT [Single]
+## Floating Twin Multiply-Add DCT [Single]
 
 X-Form
 
@@ -117,7 +107,7 @@ Special Registers Altered:
     CR1          (if Rc=1)
 ```
 
-## [DRAFT] Floating Multiply-Add FFT [Single]
+## Floating Multiply-Add FFT [Single]
 
 X-Form
 
-- 
2.30.2