JIT: Fix indir flags propagation for a couple of cases

src/coreclr/jit/gentree.cpp

@@ -9239,7 +9239,7 @@ void Compiler::gtUpdateNodeOperSideEffects(GenTree* tree)
         tree->gtFlags &= ~GTF_EXCEPT;
         if (tree->OperIsIndirOrArrMetaData())
         {
-            tree->SetIndirExceptionFlags(this);
+            tree->gtFlags |= GTF_IND_NONFAULTING;
         }
     }
 
@@ -9986,9 +9986,12 @@ bool GenTree::Precedes(GenTree* other)
 // Arguments:
 //    comp  - compiler instance
 //
+// Remarks:
+//    This should only be used for reads.
+//
 void GenTree::SetIndirExceptionFlags(Compiler* comp)
 {
-    assert(OperIsIndirOrArrMetaData());
+    assert(OperIsIndirOrArrMetaData() && OperIsUnary());
 
     if (OperMayThrow(comp))
     {

src/coreclr/jit/morphblock.cpp

@@ -1593,7 +1593,16 @@ GenTree* Compiler::fgMorphStoreDynBlock(GenTreeStoreDynBlk* tree)
     }
 
     tree->SetAllEffectsFlags(tree->Addr(), tree->Data(), tree->gtDynamicSize);
-    tree->SetIndirExceptionFlags(this);
+
+    if (tree->OperMayThrow(this))
+    {
+        tree->gtFlags |= GTF_EXCEPT;
+    }
+    else
+    {
+        tree->gtFlags |= GTF_IND_NONFAULTING;
+    }
+
     tree->gtFlags |= GTF_ASG;
 
     return tree;

src/tests/JIT/Regression/JitBlue/Runtime_79750/Runtime_79750.cs

@@ -0,0 +1,23 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Runtime.CompilerServices;
+
+class Runtime_79750
+{
+    static int Main(string[] args)
+    {
+        byte dest = 0;
+        byte source = 100;
+        uint size = GetSize();
+        Unsafe.CopyBlock(ref dest, ref GetAddr(ref source), size);
+
+        return dest;
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static ref byte GetAddr(ref byte a) => ref a;
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static uint GetSize() => 1;
+}

src/tests/JIT/Regression/JitBlue/Runtime_79750/Runtime_79750.csproj

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