JIT: fix issues in field-wise escape analysis (#114974)

Two fixes:
* we can't retype implicit byref gc struct params, as their GC info is reported by the caller.
Instead we must mark them as escaping.
* when retyping GT_STOREIND we should always use the stored data's new type

Fixes #111922.

Author: AndyAyersMS

src/coreclr/jit/objectalloc.cpp

@@ -698,12 +698,27 @@ void ObjectAllocator::MarkEscapingVarsAndBuildConnGraph()
         {
             JITDUMP("   V%02u is address exposed\n", lclNum);
             MarkLclVarAsEscaping(lclNum);
+            continue;
         }
-        else if (lclNum == comp->info.compRetBuffArg)
+
+        if (lclNum == comp->info.compRetBuffArg)
         {
             JITDUMP("   V%02u is retbuff\n", lclNum);
             MarkLclVarAsEscaping(lclNum);
+            continue;
+        }
+
+#if FEATURE_IMPLICIT_BYREFS
+        // We have to mark all implicit byref params as escaping, because
+        // their GC reporting is controlled by the caller
+        //
+        if (lclDsc->lvIsParam && lclDsc->lvIsImplicitByRef)
+        {
+            JITDUMP("   V%02u is an implicit byref param\n", lclNum);
+            MarkLclVarAsEscaping(lclNum);
+            continue;
         }
+#endif
 
         // Parameters have unknown initial values.
         // OSR locals have unknown initial values.
@@ -2047,8 +2062,7 @@ void ObjectAllocator::UpdateAncestorTypes(GenTree*              tree,
 
                     // If we are storing to a GC struct field, we may need to retype the store
                     //
-                    if (retypeFields && parent->OperIs(GT_STOREIND) && (addr->OperIs(GT_FIELD_ADDR)) &&
-                        (varTypeIsGC(parent->TypeGet())))
+                    if (parent->OperIs(GT_STOREIND) && addr->OperIs(GT_FIELD_ADDR) && varTypeIsGC(parent->TypeGet()))
                     {
                         parent->ChangeType(newType);
                     }

src/tests/JIT/opt/ObjectStackAllocation/Runtime_111922.cs

@@ -0,0 +1,108 @@
+// 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.Reflection;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using Xunit;
+
+class C1
+{
+    public C1(int x) { a = x; b = x; }
+    public int a;
+    public int b;
+}
+
+struct S1
+{
+    public S1(C1 z) { c = z; }
+    public int a;
+    public int b;
+    public C1 c;
+}
+
+public class Runtime_111922
+{
+   [Fact]
+   public static int Problem()
+   {
+       S1 s = new S1(new C1(4));
+       return 95 + SubProblem(1, s);
+   }
+
+   [MethodImpl(MethodImplOptions.NoInlining)]
+   static int SubProblem(int x, S1 s)
+   {
+       s = new S1(new C1(5));
+
+       SideEffect();
+
+       C1 v = s.c;
+       return v.a;
+   }
+
+   [Fact]
+   public static int Problem1()
+   {
+       S1 s = new S1(new C1(4));
+       return 95 + SubProblem1(1, ref s);
+   }
+
+   [MethodImpl(MethodImplOptions.NoInlining)]
+   static int SubProblem1(int x, ref S1 s)
+   {
+       s = new S1(new C1(5));
+
+       SideEffect();
+
+       C1 v = s.c;
+       return v.a;
+   }
+
+   [Fact]
+   public static int Problem2()
+   {
+       S1 s = new S1(new C1(4));
+       return 91 + SubProblem2(0, s) + SubProblem2(1, s);
+   }
+
+   [MethodImpl(MethodImplOptions.NoInlining)]
+   static int SubProblem2(int x, S1 s)
+   {
+       if (x == 0)
+       {
+           s = new S1(new C1(5));
+       }
+
+       SideEffect();
+
+       C1 v = s.c;
+       return v.a;
+   }
+
+   [Fact]
+   public static int Problem3()
+   {
+       C1 c = new C1(6);
+       return 1 + SubProblem3(0, c, c, c, c, c, c, c, c) + SubProblem3(1, c, c, c, c, c, c, c, c);
+   }
+
+   [MethodImpl(MethodImplOptions.NoInlining)]
+   static int SubProblem3(int x, C1 c1, C1 c2, C1 c3, C1 c4, C1 c5, C1 c6, C1 c7, C1 c8)
+   {
+       if (x == 0)
+       {
+           c1 = new C1(7);
+           c8 = new C1(8);
+       }
+
+       SideEffect();
+
+       return c1.a + c2.a + c3.a + c4.a + c5.a + c6.a + c7.a + c8.a;
+   }
+
+
+   [MethodImpl(MethodImplOptions.NoInlining)]
+   static void SideEffect() { }
+}

src/tests/JIT/opt/ObjectStackAllocation/Runtime_111922.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <DebugType>None</DebugType>
+    <Optimize>True</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>