JIT: Fix invalid zero-init suppression for untracked variables

src/coreclr/jit/optimizer.cpp

@@ -9029,9 +9029,9 @@ void Compiler::optRemoveRedundantZeroInits()
     CompAllocator   allocator(getAllocator(CMK_ZeroInit));
     LclVarRefCounts refCounts(allocator);
     BitVecTraits    bitVecTraits(lvaCount, this);
-    BitVec          zeroInitLocals = BitVecOps::MakeEmpty(&bitVecTraits);
-    bool            hasGCSafePoint = false;
-    bool            canThrow       = false;
+    BitVec          zeroInitLocals         = BitVecOps::MakeEmpty(&bitVecTraits);
+    bool            hasGCSafePoint         = false;
+    bool            hasImplicitControlFlow = false;
 
     assert(fgNodeThreading == NodeThreading::AllTrees);
 
@@ -9042,6 +9042,8 @@ void Compiler::optRemoveRedundantZeroInits()
         CompAllocator   allocator(getAllocator(CMK_ZeroInit));
         LclVarRefCounts defsInBlock(allocator);
         bool            removedTrackedDefs = false;
+        bool            hasEHSuccs         = block->HasPotentialEHSuccs(this);
+
         for (Statement* stmt = block->FirstNonPhiDef(); stmt != nullptr;)
         {
             Statement* next = stmt->GetNextStmt();
@@ -9052,10 +9054,7 @@ void Compiler::optRemoveRedundantZeroInits()
                     hasGCSafePoint = true;
                 }
 
-                if ((tree->gtFlags & GTF_EXCEPT) != 0)
-                {
-                    canThrow = true;
-                }
+                hasImplicitControlFlow |= hasEHSuccs && ((tree->gtFlags & GTF_EXCEPT) != 0);
 
                 switch (tree->gtOper)
                 {
@@ -9201,7 +9200,8 @@ void Compiler::optRemoveRedundantZeroInits()
                             }
                         }
 
-                        if (!removedExplicitZeroInit && isEntire && (!canThrow || !lclDsc->lvLiveInOutOfHndlr))
+                        if (!removedExplicitZeroInit && isEntire &&
+                            (!hasImplicitControlFlow || (lclDsc->lvTracked && !lclDsc->lvLiveInOutOfHndlr)))
                         {
                             // If compMethodRequiresPInvokeFrame() returns true, lower may later
                             // insert a call to CORINFO_HELP_INIT_PINVOKE_FRAME which is a gc-safe point.

src/tests/JIT/Regression/JitBlue/Runtime_91576/Runtime_91576.cs

@@ -0,0 +1,51 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.aa
+
+// Generated by Fuzzlyn v1.6 on 2023-09-03 15:59:01
+// Run on X64 Windows
+// Seed: 11520325105937570553
+// Reduced from 294.5 KiB to 0.7 KiB in 00:04:32
+// Debug: Outputs False
+// Release: Outputs True
+using System;
+using System.Runtime.CompilerServices;
+using Xunit;
+
+public class Runtime_91576
+{
+    [Fact]
+    public static int TestEntryPoint()
+    {
+        Assert.Throws<NullReferenceException>(() =>
+        {
+            Run(new int[1]);
+            Run(null);
+        });
+
+        return s_result;
+    }
+
+    static int s_result;
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static void Run(int[] l)
+    {
+        bool b = false;
+        try
+        {
+            int result = l[0];
+            b = true;
+        }
+        finally
+        {
+            Check(ref b);
+        }
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static void Check(ref bool b)
+    {
+        s_result = b ? 101 : 100;
+    }
+}
+

src/tests/JIT/Regression/JitBlue/Runtime_91576/Runtime_91576.csproj

@@ -0,0 +1,8 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <Optimize>True</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>