From b95c668d9005c73ec69af2ada6dff83f5171ad2a Mon Sep 17 00:00:00 2001
From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Sun, 13 Mar 2022 18:38:07 +0000
Subject: [PATCH] different (more useful) starting constant in grevlut

---
 openpower/sv/grevlut.py | 68 +++++++++++++++++++++++++++++++----------
 1 file changed, 52 insertions(+), 16 deletions(-)

diff --git a/openpower/sv/grevlut.py b/openpower/sv/grevlut.py
index 3c4cd9279..890cbb275 100644
--- a/openpower/sv/grevlut.py
+++ b/openpower/sv/grevlut.py
@@ -18,7 +18,18 @@ def dorow(imm8, step_i, chunk_size):
     return step_o
 
 def grevlut64(RA, RB, imm, iv):
-    x = RA
+    if RA is None: # RA=0
+        for i in range(6):
+            if 1<<i: break
+        x = {0: 0x5555555555555555,
+              1: 0x3333333333333333,
+              2: 0x0f0f0f0f0f0f0f0f,
+              3: 0x00ff00ff00ff00ff,
+              4: 0x0000ffff0000ffff,
+              5: 0x00000000ffffffff,
+        }[i]
+    else:
+        x = RA
     if (iv): x = ~x;
     shamt = RB & 63;
     #print (bin(shamt), bin(63))
@@ -31,41 +42,66 @@ def grevlut64(RA, RB, imm, iv):
 
 if __name__ == '__main__':
     # answer: 8888888...
-    RA = 0x5555555555555555
+    RB = 0b0000
+    imm = 0b11000110
+    x = grevlut64(None, RB, imm, 1)
+    print ("grevlut", bin(RB), bin(imm), hex(x), "\n", bin(x))
+
+    exit(0)
+
+    # answer: 8888888...
     RB = 0b0010
     imm = 0b11000110
-    x = grevlut64(RA, RB, imm, 1)
-    print ("grevlut", hex(RA), bin(RB), bin(imm), hex(x), "\n", bin(x))
+    x = grevlut64(None, RB, imm, 1)
+    print ("grevlut", bin(RB), bin(imm), hex(x), "\n", bin(x))
 
     # answer: 80808080...
     RB = 0b00110
     imm = 0b11000110
-    x = grevlut64(RA, RB, imm, 1)
-    print ("grevlut", hex(RA), bin(RB), bin(imm), hex(x), "\n", bin(x))
+    x = grevlut64(None, RB, imm, 1)
+    print ("grevlut", bin(RB), bin(imm), hex(x), "\n", bin(x))
 
     # answer: 80008000...
     RB = 0b01110
     imm = 0b11000110
-    x = grevlut64(RA, RB, imm, 1)
-    print ("grevlut", hex(RA), bin(RB), bin(imm), hex(x), "\n", bin(x))
+    x = grevlut64(None, RB, imm, 1)
+    print ("grevlut", bin(RB), bin(imm), hex(x), "\n", bin(x))
     print()
 
     # answer: 01010101...
     RB = 0b00110
     imm = 0b01101100
-    x = grevlut64(RA, RB, imm, 0)
-    print ("grevlut", hex(RA), bin(RB), bin(imm), hex(x), "\n", bin(x))
+    x = grevlut64(None, RB, imm, 0)
+    print ("grevlut", bin(RB), bin(imm), hex(x), "\n", bin(x))
 
     # answer: 00010001...
     RB = 0b01110
     imm = 0b01101100
-    x = grevlut64(RA, RB, imm, 0)
-    print ("grevlut", hex(RA), bin(RB), bin(imm), hex(x), "\n", bin(x))
+    x = grevlut64(None, RB, imm, 0)
+    print ("grevlut", bin(RB), bin(imm), hex(x), "\n", bin(x))
     print()
 
     for RB in range(64):
-        RA = 0x5555555555555555
         imm = 0b11000110
-        x = grevlut64(RA, RB, imm, 1)
-        print ("grevlut", hex(RA), bin(RB), bin(imm), hex(x), "\n", bin(x))
-        # answer: 8888888...
+        x = grevlut64(None, RB, imm, 1)
+        print ("grevlut", bin(RB), bin(imm), hex(x), "\n", bin(x))
+    print()
+
+    for RB in range(64):
+        imm = 0b01101100
+        x = grevlut64(None, RB, imm, 0)
+        print ("grevlut", bin(RB), bin(imm), hex(x), "\n", bin(x))
+    print()
+
+    for RB in range(64):
+        imm = 0b10011010
+        x = grevlut64(None, RB, imm, 1)
+        print ("grevlut", bin(RB), bin(imm), hex(x), "\n", bin(x))
+    print()
+
+    for RB in range(64):
+        imm = 0b01011001
+        x = grevlut64(None, RB, imm, 0)
+        print ("grevlut", bin(RB), bin(imm), hex(x), "\n", bin(x))
+    print()
+
-- 
2.30.2