Added CreateSpan optimization for arrays

dotnet · Oct 13, 2021 · 580ec90 · 580ec90
1 parent 0f2120d
commit 580ec90
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Showing 2 changed files with 47 additions and 9 deletions.
diff --git a/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_Conversion.cs b/src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_Conversion.cs
@@ -39,17 +39,25 @@ public override BoundNode VisitConversion(BoundConversion node)
 
             var rewrittenType = VisitType(node.Type);
 
-            // special handling for stackalloc converted to ROS<T>
-            if (node.Operand is BoundConvertedStackAllocExpression stackAllocExpression &&
-                TypeSymbol.Equals(rewrittenType.OriginalDefinition, _compilation.GetWellKnownType(WellKnownType.System_ReadOnlySpan_T), TypeCompareKind.ConsiderEverything))
+            // special handling for initializers converted to ROS<T>
+            if (TypeSymbol.Equals(rewrittenType.OriginalDefinition, _compilation.GetWellKnownType(WellKnownType.System_ReadOnlySpan_T), TypeCompareKind.ConsiderEverything))
             {
-                bool hasCreateSpanHelper = _compilation.GetWellKnownTypeMember(WellKnownMember.System_Runtime_CompilerServices_RuntimeHelpers__CreateSpan_T) is not null;
-                var elementType = stackAllocExpression.ElementType;
-                var initializerOpt = stackAllocExpression.InitializerOpt;
-                if (CodeGen.CodeGenerator.UseCreateSpanForReadOnlyStackAlloc(hasCreateSpanHelper, elementType, initializerOpt,
-                    /* TODO: how to find out if this is ENC? */ supportsPrivateImplClass: true))
+                if (node.Operand is BoundConvertedStackAllocExpression or BoundArrayCreation)
                 {
-                    return new BoundConvertedStackAllocExpression(stackAllocExpression.Syntax, elementType, VisitExpression(stackAllocExpression.Count), initializerOpt, rewrittenType);
+                    bool hasCreateSpanHelper = _compilation.GetWellKnownTypeMember(WellKnownMember.System_Runtime_CompilerServices_RuntimeHelpers__CreateSpan_T) is not null;
+
+                    var (elementType, initializerOpt, count) = node.Operand switch
+                    {
+                        BoundConvertedStackAllocExpression stackAlloc => (stackAlloc.ElementType, stackAlloc.InitializerOpt, VisitExpression(stackAlloc.Count)),
+                        BoundArrayCreation arrayCreation => (((ArrayTypeSymbol)arrayCreation.Type).ElementType, arrayCreation.InitializerOpt, /* need some dummy expression */ _factory.Literal(0)),
+                        _ => throw ExceptionUtilities.Unreachable
+                    };
+
+                    if (CodeGen.CodeGenerator.UseCreateSpanForReadOnlyStackAlloc(hasCreateSpanHelper, elementType, initializerOpt,
+                        /* TODO: how to find out if this is ENC? */ supportsPrivateImplClass: true))
+                    {
+                        return new BoundConvertedStackAllocExpression(node.Operand.Syntax, elementType, count, initializerOpt, rewrittenType);
+                    }
                 }
             }
 

diff --git a/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenStackAllocInitializerTests.cs b/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenStackAllocInitializerTests.cs
@@ -987,6 +987,36 @@ .maxstack  4
 ");
         }
 
+        [Fact]
+        public void TestArray()
+        {
+            var comp = CreateCompilation(new[] { @"
+using System;
+static class C
+{
+    static void Main(int i)
+    {
+        ReadOnlySpan<int> p = new int[] { 1, 2, 3 };
+        Write(p);
+    }
+
+    static void Write(ReadOnlySpan<int> span) {}
+}
+", CreateSpanDefinition }, targetFramework: TargetFramework.Net50);
+            CompileAndVerify(comp, verify: Verification.Fails)
+                .VerifyIL("C.Main",
+@"
+{
+  // Code size       16 (0x10)
+  .maxstack  1
+  IL_0000:  ldtoken    ""<PrivateImplementationDetails>.__StaticArrayInitTypeSize=12 <PrivateImplementationDetails>.4636993D3E1DA4E9D6B8F87B79E8F7C6D018580D52661950EABC3845C5897A4D""
+  IL_0005:  call       ""System.ReadOnlySpan<int> System.Runtime.CompilerServices.RuntimeHelpers.CreateSpan<int>(System.RuntimeFieldHandle)""
+  IL_000a:  call       ""void C.Write(System.ReadOnlySpan<int>)""
+  IL_000f:  ret
+}
+");
+        }
+
         private static string GetSource(string pointerType) => $@"
 using System;
 using T = {pointerType};