From c566378507153007262072645847639cc0c5cc85 Mon Sep 17 00:00:00 2001
From: Jakob Botsch Nielsen <jakob.botsch.nielsen@gmail.com>
Date: Wed, 19 Jul 2023 13:18:12 +0200
Subject: [PATCH] JIT: Expand inlined delegate calls in correct order

The access of the target instance was incorrectly inserted right after
the location of the delegate instance. Since this indirection can throw
a NRE this is incorrect; to get the proper inlined behavior, the
indirection must happen only after all arguments have been evaluated.

Fix #75832
---
 src/coreclr/jit/lower.cpp                     |  9 ++++-
 .../JitBlue/Runtime_75832/Runtime_75832.cs    | 38 +++++++++++++++++++
 .../Runtime_75832/Runtime_75832.csproj        |  9 +++++
 3 files changed, 54 insertions(+), 2 deletions(-)
 create mode 100644 src/tests/JIT/Regression/JitBlue/Runtime_75832/Runtime_75832.cs
 create mode 100644 src/tests/JIT/Regression/JitBlue/Runtime_75832/Runtime_75832.csproj

diff --git a/src/coreclr/jit/lower.cpp b/src/coreclr/jit/lower.cpp
index 79b10a5201fcf..157fda65dbf2b 100644
--- a/src/coreclr/jit/lower.cpp
+++ b/src/coreclr/jit/lower.cpp
@@ -4958,9 +4958,14 @@ GenTree* Lowering::LowerDelegateInvoke(GenTreeCall* call)
 
     GenTree* newThis = comp->gtNewIndir(TYP_REF, newThisAddr);
 
-    BlockRange().InsertAfter(thisExpr, newThisAddr, newThis);
-
+    // Insert the new 'this' arg right before the call to get the correct null
+    // behavior (the NRE that would logically happen inside Delegate.Invoke
+    // should happen after all args are evaluated). We must also move the
+    // PUTARG_REG node ahead.
     thisArgNode->AsOp()->gtOp1 = newThis;
+    BlockRange().Remove(thisArgNode);
+    BlockRange().InsertBefore(call, newThisAddr, newThis, thisArgNode);
+
     ContainCheckIndir(newThis->AsIndir());
 
     // the control target is
diff --git a/src/tests/JIT/Regression/JitBlue/Runtime_75832/Runtime_75832.cs b/src/tests/JIT/Regression/JitBlue/Runtime_75832/Runtime_75832.cs
new file mode 100644
index 0000000000000..edfcc9f177f3c
--- /dev/null
+++ b/src/tests/JIT/Regression/JitBlue/Runtime_75832/Runtime_75832.cs
@@ -0,0 +1,38 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.CompilerServices;
+using Xunit;
+
+public class Runtime_75832
+{
+    [Fact]
+    public static int TestEntryPoint()
+    {
+        try
+        {
+            Test(0);
+            Console.WriteLine("FAIL: No exception thrown");
+        }
+        catch (DivideByZeroException)
+        {
+            return 100;
+        }
+        catch (Exception ex)
+        {
+            Console.WriteLine("FAIL: Caught {0}", ex.GetType().Name);
+        }
+        
+        return 101;
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static void Test(int i)
+    {
+        GetAction()(100 / i);
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static Action<int> GetAction() => null;
+}
diff --git a/src/tests/JIT/Regression/JitBlue/Runtime_75832/Runtime_75832.csproj b/src/tests/JIT/Regression/JitBlue/Runtime_75832/Runtime_75832.csproj
new file mode 100644
index 0000000000000..1bb887ea34b0f
--- /dev/null
+++ b/src/tests/JIT/Regression/JitBlue/Runtime_75832/Runtime_75832.csproj
@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <Optimize>True</Optimize>
+    <DebugType>None</DebugType>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>
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