Fix too narrow loads while unspilling

src/coreclr/jit/codegenlinear.cpp

@@ -1213,22 +1213,15 @@ void CodeGen::genUnspillRegIfNeeded(GenTree* tree)
 // TODO-Cleanup: The following code could probably be further merged and cleaned up.
 #if defined(TARGET_XARCH) || defined(TARGET_ARM64)
             // Load local variable from its home location.
-            // In most cases the tree type will indicate the correct type to use for the load.
-            // However, if it is NOT a normalizeOnLoad lclVar (i.e. NOT a small int that always gets
-            // widened when loaded into a register), and its size is not the same as the actual register type
-            // of the lclVar, then we need to change the type of the tree node when loading.
-            // This situation happens due to "optimizations" that avoid a cast and
-            // simply retype the node when using long type lclVar as an int.
-            // While loading the int in that case would work for this use of the lclVar, if it is
-            // later used as a long, we will have incorrectly truncated the long.
-            // In the normalizeOnLoad case ins_Load will return an appropriate sign- or zero-
-            // extending load.
-            var_types lclActualType = varDsc->GetActualRegisterType();
-            assert(lclActualType != TYP_UNDEF);
-            if (spillType != lclActualType && !varTypeIsGC(spillType) && !varDsc->lvNormalizeOnLoad())
+            // Never allow truncating the locals here, otherwise a subsequent
+            // use of the local with a wider type would see the truncated
+            // value. We do allow wider loads as those can be efficient even
+            // when unaligned and might be smaller encoding wise (on xarch).
+            var_types lclLoadType = varDsc->lvNormalizeOnLoad() ? varDsc->TypeGet() : varDsc->GetActualRegisterType();
+            assert(lclLoadType != TYP_UNDEF);
+            if (genTypeSize(spillType) < genTypeSize(lclLoadType))
             {
-                assert(!varTypeIsGC(varDsc));
-                spillType = lclActualType;
+                spillType = lclLoadType;
             }
 #elif defined(TARGET_ARM)
 // No normalizing for ARM

src/tests/JIT/Regression/JitBlue/Runtime_66624/Runtime_66624.cs

@@ -0,0 +1,116 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+// Generated by Fuzzlyn v1.5 on 2022-03-14 21:20:55
+// Run on X64 Windows
+// Seed: 16520696696442011600
+// Reduced from 677.9 KiB to 2.4 KiB in 00:04:01
+// Debug: Outputs 53474
+// Release: Outputs 226
+public class C0
+{
+    public byte F0;
+    public sbyte F3;
+    public byte F4;
+    public byte F5;
+    public uint F6;
+    public C0(byte f4, byte f5, uint f6)
+    {
+        F4 = f4;
+        F5 = f5;
+        F6 = f6;
+    }
+}
+
+public class C1
+{
+    public C0 F4;
+    public C1(C0 f4)
+    {
+        F4 = f4;
+    }
+}
+
+public struct S0
+{
+    public sbyte F0;
+    public C0 F2;
+    public bool F4;
+    public ulong F5;
+    public uint F6;
+    public bool F7;
+    public S0(sbyte f0, C0 f1, C0 f2, bool f4, ulong f5, uint f6, bool f7) : this()
+    {
+        F0 = f0;
+        F2 = f2;
+        F4 = f4;
+        F5 = f5;
+        F6 = f6;
+        F7 = f7;
+    }
+}
+
+public class Runtime_66624
+{
+    public static IRuntime s_rt;
+    public static C0 s_1 = new C0(0, 0, 0);
+    public static C1[][] s_3 = new C1[][] { new C1[] { new C1(new C0(0, 0, 0)) } };
+    public static int Main()
+    {
+        CollectibleALC alc = new CollectibleALC();
+        System.Reflection.Assembly asm = alc.LoadFromAssemblyPath(System.Reflection.Assembly.GetExecutingAssembly().Location);
+        System.Reflection.MethodInfo mi = asm.GetType(typeof(Runtime_66624).FullName).GetMethod(nameof(MainInner));
+        System.Type runtimeTy = asm.GetType(typeof(Runtime).FullName);
+        return (int)mi.Invoke(null, new object[] { System.Activator.CreateInstance(runtimeTy) });
+    }
+
+    public static int MainInner(IRuntime rt)
+    {
+        s_rt = rt;
+        return M10(53474);
+    }
+
+    public static int M10(ushort arg0)
+    {
+        var vr1 = new S0[] { new S0(0, new C0(0, 0, 0), new C0(0, 0, 0), false, 0, 0, false) };
+        S0 var1 = new S0(s_1.F3, new C0(0, 0, s_3[0][0].F4.F6), new C0(0, 0, 0), true, 0, 0, false);
+        try
+        {
+            byte vr5 = var1.F2.F0;
+        }
+        finally
+        {
+            var1 = new S0(0, new C0(0, 0, 0), new C0(0, 1, 0), true, 0, 0, true);
+        }
+
+        if ((byte)arg0 < 1)
+        {
+            C0[] var4 = new C0[] { new C0(0, 0, 0) };
+        }
+
+        s_rt.WriteLine("c_4102", arg0);
+        return ((Runtime)s_rt).Result;
+    }
+}
+
+public interface IRuntime
+{
+    void WriteLine<T>(string site, T value);
+}
+
+public class Runtime : IRuntime
+{
+    public int Result;
+
+    public void WriteLine<T>(string site, T value)
+    {
+        Result = (ushort)(object)value == 53474 ? 100 : -1;
+    }
+}
+
+public class CollectibleALC : System.Runtime.Loader.AssemblyLoadContext
+{
+    public CollectibleALC() : base(true)
+    {
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_66624/Runtime_66624.csproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <Optimize>True</Optimize>
+    <CLRTestPriority>1</CLRTestPriority>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>

src/tests/issues.targets

@@ -1256,6 +1256,9 @@
         <ExcludeList Include="$(XunitTestBinBase)/JIT/Regression/JitBlue/Runtime_64883/Runtime_64883/*">
             <Issue>https://github.com/dotnet/runtimelab/issues/155: Collectible assemblies</Issue>
         </ExcludeList>
+        <ExcludeList Include="$(XunitTestBinBase)/JIT/Regression/JitBlue/Runtime_66624/Runtime_66624/*">
+            <Issue>https://github.com/dotnet/runtimelab/issues/155: Collectible assemblies</Issue>
+        </ExcludeList>
         <ExcludeList Include="$(XunitTestBinBase)/Loader/ContextualReflection/ContextualReflection/*">
             <Issue>https://github.com/dotnet/runtimelab/issues/165</Issue>
         </ExcludeList>
@@ -3422,6 +3425,9 @@
         <ExcludeList Include="$(XunitTestBinBase)/JIT/Regression/JitBlue/Runtime_64883/Runtime_64883/*">
             <Issue>Loads an assembly from file</Issue>
         </ExcludeList>
+        <ExcludeList Include="$(XunitTestBinBase)/JIT/Regression/JitBlue/Runtime_66624/Runtime_66624/*">
+            <Issue>Loads an assembly from file</Issue>
+        </ExcludeList>
         <ExcludeList Include = "$(XunitTestBinBase)/tracing/eventcounter/incrementingeventcounter/**">
             <Issue>System.Threading.Thread.UnsafeStart not supported</Issue>
         </ExcludeList>