From 5e360a4f058a6497a5c750fa98b9cd15cd2000a0 Mon Sep 17 00:00:00 2001
From: Peter Dettman <peter.dettman@bouncycastle.org>
Date: Sun, 20 Nov 2022 01:52:09 +0700
Subject: Use BitOperations for clz, ctz

---
 crypto/src/util/Integers.cs | 20 ++++++++------------
 crypto/src/util/Longs.cs    | 20 ++++++++------------
 2 files changed, 16 insertions(+), 24 deletions(-)

diff --git a/crypto/src/util/Integers.cs b/crypto/src/util/Integers.cs
index ab1868b74..eff7056b6 100644
--- a/crypto/src/util/Integers.cs
+++ b/crypto/src/util/Integers.cs
@@ -16,9 +16,11 @@ namespace Org.BouncyCastle.Utilities
         public const int NumBits = 32;
         public const int NumBytes = 4;
 
+#if !NETCOREAPP3_0_OR_GREATER
         private static readonly byte[] DeBruijnTZ = {
             0x1F, 0x00, 0x1B, 0x01, 0x1C, 0x0D, 0x17, 0x02, 0x1D, 0x15, 0x13, 0x0E, 0x18, 0x10, 0x03, 0x07,
             0x1E, 0x1A, 0x0C, 0x16, 0x14, 0x12, 0x0F, 0x06, 0x19, 0x0B, 0x11, 0x05, 0x0A, 0x04, 0x09, 0x08 };
+#endif
 
         public static int HighestOneBit(int i)
         {
@@ -50,12 +52,8 @@ namespace Org.BouncyCastle.Utilities
         public static int NumberOfLeadingZeros(int i)
         {
 #if NETCOREAPP3_0_OR_GREATER
-            if (Lzcnt.IsSupported)
-            {
-                return (int)Lzcnt.LeadingZeroCount((uint)i);
-            }
-#endif
-
+            return BitOperations.LeadingZeroCount((uint)i);
+#else
             if (i <= 0)
                 return (~i >> (31 - 5)) & (1 << 5);
 
@@ -67,20 +65,18 @@ namespace Org.BouncyCastle.Utilities
             if (0 == (u >> 30)) { n +=  2; u <<=  2; }
             n -= (int)(u >> 31);
             return n;
+#endif
         }
 
         public static int NumberOfTrailingZeros(int i)
         {
 #if NETCOREAPP3_0_OR_GREATER
-            if (Bmi1.IsSupported)
-            {
-                return (int)Bmi1.TrailingZeroCount((uint)i);
-            }
-#endif
-
+            return BitOperations.TrailingZeroCount(i);
+#else
             int n = DeBruijnTZ[(uint)((i & -i) * 0x0EF96A62) >> 27];
             int m = (((i & 0xFFFF) | (int)((uint)i >> 16)) - 1) >> 31;
             return n - m;
+#endif
         }
 
         public static int Reverse(int i)
diff --git a/crypto/src/util/Longs.cs b/crypto/src/util/Longs.cs
index 02ffb7676..18be945e9 100644
--- a/crypto/src/util/Longs.cs
+++ b/crypto/src/util/Longs.cs
@@ -16,11 +16,13 @@ namespace Org.BouncyCastle.Utilities
         public const int NumBits = 64;
         public const int NumBytes = 8;
 
+#if !NETCOREAPP3_0_OR_GREATER
         private static readonly byte[] DeBruijnTZ = {
             0x3F, 0x00, 0x01, 0x34, 0x02, 0x06, 0x35, 0x1A, 0x03, 0x25, 0x28, 0x07, 0x21, 0x36, 0x2F, 0x1B,
             0x3D, 0x04, 0x26, 0x2D, 0x2B, 0x29, 0x15, 0x08, 0x17, 0x22, 0x3A, 0x37, 0x30, 0x11, 0x1C, 0x0A,
             0x3E, 0x33, 0x05, 0x19, 0x24, 0x27, 0x20, 0x2E, 0x3C, 0x2C, 0x2A, 0x14, 0x16, 0x39, 0x10, 0x09,
             0x32, 0x18, 0x23, 0x1F, 0x3B, 0x13, 0x38, 0x0F, 0x31, 0x1E, 0x12, 0x0E, 0x1D, 0x0D, 0x0C, 0x0B };
+#endif
 
         public static long HighestOneBit(long i)
         {
@@ -53,12 +55,8 @@ namespace Org.BouncyCastle.Utilities
         public static int NumberOfLeadingZeros(long i)
         {
 #if NETCOREAPP3_0_OR_GREATER
-            if (Lzcnt.X64.IsSupported)
-            {
-                return (int)Lzcnt.X64.LeadingZeroCount((ulong)i);
-            }
-#endif
-
+            return BitOperations.LeadingZeroCount((ulong)i);
+#else
             int x = (int)(i >> 32), n = 0;
             if (x == 0)
             {
@@ -66,20 +64,18 @@ namespace Org.BouncyCastle.Utilities
                 x = (int)i;
             }
             return n + Integers.NumberOfLeadingZeros(x);
+#endif
         }
 
         public static int NumberOfTrailingZeros(long i)
         {
 #if NETCOREAPP3_0_OR_GREATER
-            if (Bmi1.X64.IsSupported)
-            {
-                return (int)Bmi1.X64.TrailingZeroCount((ulong)i);
-            }
-#endif
-
+            return BitOperations.TrailingZeroCount((ulong)i);
+#else
             int n = DeBruijnTZ[(uint)((ulong)((i & -i) * 0x045FBAC7992A70DAL) >> 58)];
             long m = (((i & 0xFFFFFFFFL) | (long)((ulong)i >> 32)) - 1L) >> 63;
             return n - (int)m;
+#endif
         }
 
         public static long Reverse(long i)
-- 
cgit 1.4.1