From: lkcl <lkcl@web>
Date: Thu, 22 Sep 2022 22:00:44 +0000 (+0100)
Subject: (no commit message)
X-Git-Tag: opf_rfc_ls005_v1~325
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=46b30f99f5bbea6cfee1f15a2e51cf0b57dacd7d;p=libreriscv.git

---

diff --git a/openpower/sv/svp64/appendix.mdwn b/openpower/sv/svp64/appendix.mdwn
index 4018947cb..56dc90cd2 100644
--- a/openpower/sv/svp64/appendix.mdwn
+++ b/openpower/sv/svp64/appendix.mdwn
@@ -673,17 +673,14 @@ the CR Register, not to individual bits within the CR register.
 
 The `CR{n}` notation is designed to give *linear sequential
 numbering* in the Vector domain on a straight sequential Vector Loop.
-Without it, there is the risk of massive confusion as CR Fields
-could be accessed in order `CR7 CR6 ... CR0 CR15 CR14 .. CR8 CR23..`
-in Vector Loops.
 
 In OpenPOWER v3.0/1, BF/BT/BA/BB are all 5 bits.  The top 3 bits (0:2)
 select one of the 8 CRs; the bottom 2 bits (3:4) select one of 4 bits
 *in* that CR (EQ/LT/GT/SO).  The numbering was determined (after 4 months of
 analysis and research) to be as follows:
 
-    CR_index = 7-(BA>>2)      # top 3 bits but de-MSB0'd
-    bit_index = 3-(BA & 0b11) # low 2 bits but de-MSB0'd
+    CR_index = (BA>>2)      # top 3 bits
+    bit_index = (BA & 0b11) # low 2 bits
     CR_reg = CR{CR_index}     # get the CR
     # finally get the bit from the CR.
     CR_bit = (CR_reg & (1<<bit_index)) != 0
@@ -708,7 +705,7 @@ applies, **not** the `CR_bit` portion (bits 3-4):
 Thus, for example, to access a given bit for a CR in SV mode, the v3.0B
 algorithm to determine CR\_reg is modified to as follows:
 
-    CR_index = 7-(BA>>2)      # top 3 bits but BE
+    CR_index = (BA>>2)      # top 3 bits 
     if spec[0]:
         # vector mode, 0-124 increments of 4
         CR_index = (CR_index<<4) | (spec[1:2] << 2)
@@ -716,7 +713,7 @@ algorithm to determine CR\_reg is modified to as follows:
         # scalar mode, 0-32 increments of 1
         CR_index = (spec[1:2]<<3) | CR_index
     # same as for v3.0/v3.1 from this point onwards
-    bit_index = 3-(BA & 0b11) # low 2 bits but BE
+    bit_index = (BA & 0b11) # low 2 bits
     CR_reg = CR{CR_index}     # get the CR
     # finally get the bit from the CR.
     CR_bit = (CR_reg & (1<<bit_index)) != 0