Optimize Log2FloorNonZero with LZCNT

master131 · Dec 24, 2018 · 873680d · 873680d
1 parent 4f46f1b
commit 873680d
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Showing 2 changed files with 11 additions and 1 deletion.
diff --git a/BrotliSharpLib/BrotliSharpLib.csproj b/BrotliSharpLib/BrotliSharpLib.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
 	<PropertyGroup>
-		<TargetFrameworks>net20;net35;net40;net45;net451;net452;net462;netstandard1.3;netstandard1.6;netstandard2.0;netcoreapp1.0;netcoreapp1.1</TargetFrameworks>
+		<TargetFrameworks>net20;net35;net40;net45;net451;net452;net462;netstandard1.3;netstandard1.6;netstandard2.0;netcoreapp1.0;netcoreapp1.1;netcoreapp3.0</TargetFrameworks>
 		<AllowUnsafeBlocks>True</AllowUnsafeBlocks>
 		<GenerateDocumentationFile>true</GenerateDocumentationFile>
 		<NoWarn>1570;1701</NoWarn>

diff --git a/BrotliSharpLib/Encode/FastLog.cs b/BrotliSharpLib/Encode/FastLog.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Runtime.CompilerServices;
 using size_t = BrotliSharpLib.Brotli.SizeT;
 
 namespace BrotliSharpLib {
@@ -106,7 +107,16 @@ private static double FastLog2(size_t v) {
             return Math.Log(v) * LOG_2_INV;
         }
 
+#if AGGRESSIVE_INLINING
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+#endif
         private static uint Log2FloorNonZero(size_t n) {
+#if NETCOREAPP3_0
+            if (System.Runtime.Intrinsics.X86.Lzcnt.IsSupported)
+            {
+                return 31u ^ (uint)System.Runtime.Intrinsics.X86.Lzcnt.LeadingZeroCount((uint)n | 1);
+            }
+#endif
             size_t m = n;
             uint result = 0;
             while ((m >>= 1) != 0) result++;