From: Jacob Lifshay <programmerjake@gmail.com>
Date: Wed, 20 Sep 2023 22:38:37 +0000 (-0700)
Subject: make scalar EXTRA2 encoding match between tables and algorithms
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=refs%2Fheads%2Ffix-scalar-extra2;p=libreriscv.git

make scalar EXTRA2 encoding match between tables and algorithms

Fixes: https://bugs.libre-soc.org/show_bug.cgi?id=1161
---

diff --git a/openpower/sv/svp64.mdwn b/openpower/sv/svp64.mdwn
index c623c123a..227abd8ce 100644
--- a/openpower/sv/svp64.mdwn
+++ b/openpower/sv/svp64.mdwn
@@ -1195,8 +1195,10 @@ A pseudocode algorithm explains the relationship, for INT/FP (see
 ```
     if extra3_mode:
         spec = EXTRA3
-    else:
-        spec = EXTRA2 << 1 # same as EXTRA3, shifted
+    elif EXTRA2[0]:  # vector mode, can express even registers in r0-126
+        spec = EXTRA2 << 1  # same as EXTRA3, shifted
+    else:            # scalar mode, can express registers in r0-63
+        spec = (EXTRA2[0] << 2) | EXTRA2[1]
     if spec[0]: # vector
          return (RA << 2) | spec[1:2]
     else:         # scalar
diff --git a/openpower/sv/svp64/appendix.mdwn b/openpower/sv/svp64/appendix.mdwn
index 73426d430..25c62d769 100644
--- a/openpower/sv/svp64/appendix.mdwn
+++ b/openpower/sv/svp64/appendix.mdwn
@@ -616,8 +616,10 @@ applies, **not** the `CR_bit` portion (bits 3-4):
 ```
     if extra3_mode:
         spec = EXTRA3
-    else:
-        spec = EXTRA2<<1 | 0b0
+    elif EXTRA2[0]:  # vector mode
+        spec = EXTRA2 << 1  # same as EXTRA3, shifted
+    else:            # scalar mode
+        spec = (EXTRA2[0] << 2) | EXTRA2[1]
     if spec[0]:
        # vector constructs "BA[0:2] spec[1:2] 00 BA[3:4]"
        return ((BA >> 2)<<6) | # hi 3 bits shifted up