#475 reusing the whole ILGenerator with the m_scope tokens and m_ILStream; exposing more of the FEC IL gen stuff

Author: dadhi

src/FastExpressionCompiler/FastExpressionCompiler.cs

@@ -2333,7 +2333,7 @@ public static bool TryEmit(Expression expr,
 
                         case ExpressionType.Default:
                             if (exprType != typeof(void) && (parent & ParentFlags.IgnoreResult) == 0)
-                                EmitDefault(exprType, il);
+                                EmitDefault(il, exprType);
                             return true;
 
                         case ExpressionType.Index:
@@ -2690,7 +2690,8 @@ private static bool TryEmitCoalesceOperator(BinaryExpression expr, IReadOnlyList
                 return il.EmitPopIfIgnoreResult(parent);
             }
 
-            private static void EmitDefault(Type type, ILGenerator il)
+            /// <summary>Emit default op code for the type</summary>
+            public static void EmitDefault(ILGenerator il, Type type)
             {
                 if (type.IsClass)
                 {
@@ -6216,8 +6217,9 @@ private static void EmitLoadLocalVariableAddress(ILGenerator il, int location)
                     il.Demit(OpCodes.Ldloca, (short)location);
             }
 
+            /// <summary>Load local variable on stack</summary>
             [MethodImpl((MethodImplOptions)256)]
-            internal static bool EmitLoadLocalVariable(ILGenerator il, int location)
+            public static bool EmitLoadLocalVariable(ILGenerator il, int location)
             {
                 if (location == 0)
                     il.Demit(OpCodes.Ldloc_0);
@@ -6267,8 +6269,9 @@ private static int EmitStoreLocalVariable(ILGenerator il, Type type)
                 return location;
             }
 
+            /// <summary>Stores and loads the variable</summary>
             [MethodImpl((MethodImplOptions)256)]
-            internal static void EmitStoreAndLoadLocalVariable(ILGenerator il, int location)
+            public static void EmitStoreAndLoadLocalVariable(ILGenerator il, int location)
             {
                 if (location == 0)
                 {
@@ -6302,7 +6305,8 @@ internal static void EmitStoreAndLoadLocalVariable(ILGenerator il, int location)
                 }
             }
 
-            internal static int EmitStoreAndLoadLocalVariable(ILGenerator il, Type t)
+            /// <summary>Stores and loads the variable, and returns it</summary>
+            public static int EmitStoreAndLoadLocalVariable(ILGenerator il, Type t)
             {
                 var location = il.GetNextLocalVarIndex(t);
                 EmitStoreAndLoadLocalVariable(il, location);
@@ -8150,7 +8154,7 @@ public static T GetFirst<T>(this IEnumerable<T> source)
     }
 
     [RequiresUnreferencedCode(Trimming.Message)]
-    internal static class ILGeneratorTools
+    public static class ILGeneratorTools
     {
 #if DEMIT
         [MethodImpl((MethodImplOptions)256)]

test/FastExpressionCompiler.Benchmarks/Issue468_Compile_vs_FastCompile.cs

@@ -287,17 +287,37 @@ public object CompiledFast()
 public class Issue475_ReuseVsNoReuse
 {
     /*
-    
+    ## Baseline
+
+    BenchmarkDotNet v0.14.0, Windows 11 (10.0.26100.3915)
+    Intel Core i9-8950HK CPU 2.90GHz (Coffee Lake), 1 CPU, 12 logical and 6 physical cores
+    .NET SDK 9.0.203
+    [Host]     : .NET 9.0.4 (9.0.425.16305), X64 RyuJIT AVX2
+    DefaultJob : .NET 9.0.4 (9.0.425.16305), X64 RyuJIT AVX2
+
+
+    | Method             | Mean     | Error     | StdDev    | Ratio | RatioSD | Rank | Gen0   | Gen1   | Allocated | Alloc Ratio |
+    |------------------- |---------:|----------:|----------:|------:|--------:|-----:|-------:|-------:|----------:|------------:|
+    | ReuseILGenerator   | 5.317 us | 0.1028 us | 0.1441 us |  0.95 |    0.04 |    1 | 0.3510 | 0.3433 |   2.16 KB |        0.94 |
+    | NoReuseILGenerator | 5.602 us | 0.1085 us | 0.1590 us |  1.00 |    0.04 |    1 | 0.3738 | 0.3586 |    2.3 KB |        1.00 |
+
+    ## Reusing the whole ILGenerator with the m_scope tokens and m_ILStream
+
+    | Method             | Mean     | Error     | StdDev    | Ratio | RatioSD | Rank | Gen0   | Gen1   | Allocated | Alloc Ratio |
+    |------------------- |---------:|----------:|----------:|------:|--------:|-----:|-------:|-------:|----------:|------------:|
+    | ReuseILGenerator   | 4.531 us | 0.0898 us | 0.1451 us |  0.87 |    0.04 |    1 | 0.2747 | 0.2670 |   1.71 KB |        0.74 |
+    | NoReuseILGenerator | 5.211 us | 0.1025 us | 0.1874 us |  1.00 |    0.05 |    2 | 0.3738 | 0.3586 |    2.3 KB |        1.00 |
+
     */
     [Benchmark(Baseline = true)]
-    public object NoReuse()
+    public object NoReuseILGenerator()
     {
-        return IssueTests.Issue475_Reuse_DynamicMethod_if_possible.NoReuse();
+        return IssueTests.Issue475_Reuse_DynamicMethod_if_possible.NoReuseILGenerator();
     }
 
     [Benchmark]
-    public object Reuse()
+    public object ReuseILGenerator()
     {
-        return IssueTests.Issue475_Reuse_DynamicMethod_if_possible.Reuse();
+        return IssueTests.Issue475_Reuse_DynamicMethod_if_possible.ReuseILGenerator();
     }
 }