Fix issue with hoisting and copy prop interaction (#85493)

* Fix issue with hoisting and copy prop interaction

After hoisting creates a tree copy, it morphs it. That morph might
lose the value numbers on LCL_VAR uses, but leave the SSA numbers.
Copy prop was assuming that such a use had a VN. Instead, check this
dynamically instead of asserting.

Fixes #84619

* Further optimize cast in fgOptimizeCastOnStore()

If we optimize the cast, call `fgOptimizeCast` to see if it can be
optimized further.

* Add regression test

* Feedback

src/coreclr/jit/copyprop.cpp

@@ -158,7 +158,8 @@ int Compiler::optCopyProp_LclVarScore(const LclVarDsc* lclVarDsc, const LclVarDs
 bool Compiler::optCopyProp(
     BasicBlock* block, Statement* stmt, GenTreeLclVarCommon* tree, unsigned lclNum, LclNumToLiveDefsMap* curSsaName)
 {
-    assert(((tree->gtFlags & GTF_VAR_DEF) == 0) && (tree->GetLclNum() == lclNum) && tree->gtVNPair.BothDefined());
+    assert((tree->gtFlags & GTF_VAR_DEF) == 0);
+    assert(tree->GetLclNum() == lclNum);
 
     bool       madeChanges = false;
     LclVarDsc* varDsc      = lvaGetDesc(lclNum);

src/coreclr/jit/morph.cpp

@@ -10196,6 +10196,9 @@ GenTree* Compiler::fgOptimizeCastOnStore(GenTree* store)
     {
         // This is a type-changing cast so we cannot remove it entirely.
         cast->gtCastType = genActualType(castToType);
+
+        // See if we can optimize the new cast.
+        store->Data() = fgOptimizeCast(cast);
     }
 
     return store;

src/tests/JIT/Regression/JitBlue/Runtime_84619/Runtime_84619.cs

@@ -0,0 +1,28 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Xunit;
+
+// Generated by Fuzzlyn v1.5 on 2023-04-09 16:37:03
+// Run on X64 Windows
+// Seed: 6230188300048624105
+// Reduced from 155.1 KiB to 0.2 KiB in 00:01:48
+// Hits JIT assert in Release:
+// Assertion failed '((tree->gtFlags & GTF_VAR_DEF) == 0) && (tree->GetLclNum() == lclNum) && tree->gtVNPair.BothDefined()' in 'Program:Main(Fuzzlyn.ExecutionServer.IRuntime)' during 'VN based copy prop' (IL size 25; hash 0xade6b36b; FullOpts)
+// 
+//     File: D:\a\_work\1\s\src\coreclr\jit\copyprop.cpp Line: 161
+// 
+public class Runtime_84619
+{
+    public static sbyte s_27;
+    [Fact]
+    public static int TestEntryPoint()
+    {
+        long vr1 = 0;
+        for (int vr3 = 0; vr3 < -1; vr3++)
+        {
+            s_27 = (sbyte)(vr1 | vr1);
+        }
+        return 100;
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_84619/Runtime_84619.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>