From c4f5f0d45f8ed4516f2e2eb3da5881eb3f7459f3 Mon Sep 17 00:00:00 2001
From: Tim <cassell.timothy@gmail.com>
Date: Thu, 8 Jun 2023 18:28:10 -0400
Subject: [PATCH] Remove `Unsafe.SkipInit`, just use `default`.

---
 .../Code/DeclarationsProvider.cs              | 13 +-----
 .../Emitters/ConsumableConsumeEmitter.cs      | 42 -------------------
 .../Toolchains/Roslyn/Generator.cs            |  4 +-
 3 files changed, 2 insertions(+), 57 deletions(-)

diff --git a/src/BenchmarkDotNet/Code/DeclarationsProvider.cs b/src/BenchmarkDotNet/Code/DeclarationsProvider.cs
index 995fd3f557..4b8f349962 100644
--- a/src/BenchmarkDotNet/Code/DeclarationsProvider.cs
+++ b/src/BenchmarkDotNet/Code/DeclarationsProvider.cs
@@ -86,18 +86,7 @@ public override string ConsumeField
                 : null;
 
         public override string OverheadImplementation
-        {
-            get
-            {
-                var type = WorkloadMethodReturnType;
-                // ByRefLike types and pointers use default, everything else uses Unsafe.SkipInit.
-                if (type.IsByRefLike() || type.IsPointer)
-                {
-                    return $"return default({type.GetCorrectCSharpTypeName()});";
-                }
-                return $"System.Runtime.CompilerServices.Unsafe.SkipInit(out {type.GetCorrectCSharpTypeName()} value);\nreturn value;";
-            }
-        }
+            => $"return default({WorkloadMethodReturnType.GetCorrectCSharpTypeName()});";
 
         public override string ReturnsDefinition
             => Consumer.IsConsumable(WorkloadMethodReturnType) || Consumer.HasConsumableField(WorkloadMethodReturnType, out _)
diff --git a/src/BenchmarkDotNet/Toolchains/InProcess/Emit/Implementation/Emitters/ConsumableConsumeEmitter.cs b/src/BenchmarkDotNet/Toolchains/InProcess/Emit/Implementation/Emitters/ConsumableConsumeEmitter.cs
index 2bc87cc487..790ca54482 100644
--- a/src/BenchmarkDotNet/Toolchains/InProcess/Emit/Implementation/Emitters/ConsumableConsumeEmitter.cs
+++ b/src/BenchmarkDotNet/Toolchains/InProcess/Emit/Implementation/Emitters/ConsumableConsumeEmitter.cs
@@ -78,48 +78,6 @@ protected override void OnEmitCtorBodyOverride(ConstructorBuilder constructorBui
             ilBuilder.Emit(OpCodes.Stfld, consumerField);
         }
 
-        public override void EmitOverheadImplementation(ILGenerator ilBuilder, Type returnType)
-        {
-            // ByRefLike types and pointers use default, everything else uses Unsafe.SkipInit.
-            if (returnType.IsByRefLike() || returnType.IsPointer)
-            {
-                /*
-                    // return default;
-                    IL_0000: ldc.i4.0
-                    IL_0001: ret
-                 */
-                // optional local if default(T) uses .initobj
-                var optionalLocalForInitobj = ilBuilder.DeclareOptionalLocalForReturnDefault(returnType);
-                ilBuilder.EmitReturnDefault(returnType, optionalLocalForInitobj);
-                return;
-            }
-
-            /*
-                // System.Runtime.CompilerServices.Unsafe.SkipInit(out BenchmarkDotNet.Samples.CustomWithConsumable value);
-                // return value;
-                .locals init (
-                    [0] valuetype BenchmarkDotNet.Samples.CustomWithConsumable
-                )
-
-                IL_0000: ldloca.s 0
-                IL_0002: call void Unsafe::SkipInit<valuetype BenchmarkDotNet.Samples.CustomWithConsumable>(!!0&)
-                IL_0007: ldloc.0
-                IL_0008: ret
-             */
-            var local = ilBuilder.DeclareLocal(returnType);
-            ilBuilder.EmitLdloca(local);
-            ilBuilder.Emit(OpCodes.Call, GetGenericSkipInitMethod(returnType));
-            ilBuilder.EmitLdloc(local);
-            ilBuilder.Emit(OpCodes.Ret);
-        }
-
-        private static MethodInfo GetGenericSkipInitMethod(Type skipInitType)
-        {
-            return typeof(Unsafe).GetMethods(BindingFlags.Static | BindingFlags.Public)
-                .Single(m => m.Name == nameof(Unsafe.SkipInit) && m.IsGenericMethodDefinition && m.ReturnType == typeof(void) && m.GetParameters().Single().IsOut)
-                .MakeGenericMethod(skipInitType);
-        }
-
         protected override void EmitActionBeforeCallOverride(ILGenerator ilBuilder)
         {
             /*
diff --git a/src/BenchmarkDotNet/Toolchains/Roslyn/Generator.cs b/src/BenchmarkDotNet/Toolchains/Roslyn/Generator.cs
index 3730081e92..0718d6b8cb 100644
--- a/src/BenchmarkDotNet/Toolchains/Roslyn/Generator.cs
+++ b/src/BenchmarkDotNet/Toolchains/Roslyn/Generator.cs
@@ -2,7 +2,6 @@
 using System.IO;
 using System.Linq;
 using System.Reflection;
-using System.Runtime.CompilerServices;
 using BenchmarkDotNet.Extensions;
 using BenchmarkDotNet.Portability;
 using BenchmarkDotNet.Running;
@@ -57,8 +56,7 @@ internal static IEnumerable<Assembly> GetAllReferences(BenchmarkCase benchmarkCa
                     new[]
                     {
                         benchmarkCase.Descriptor.Type.GetTypeInfo().Assembly, // this assembly does not has to have a reference to BenchmarkDotNet (e.g. custom framework for benchmarking that internally uses BenchmarkDotNet
-                        typeof(BenchmarkCase).Assembly, // BenchmarkDotNet
-                        typeof(Unsafe).Assembly // Unsafe
+                        typeof(BenchmarkCase).Assembly // BenchmarkDotNet
                     })
                 .Distinct();
     }