[release/9.0-staging] JIT: fix local assertion prop error for partial local comparisons (#112539)

* JIT: fix local assertion prop error for partial local comparisons

If a JTRUE comparison only involves part of a local value we cannot make assertions
about the local as a whole.

Fixes #111352.

* restrict to TYP_LONG locals

---------

Co-authored-by: Andy Ayers <[email protected]>

Author: github-actions[bot]

src/coreclr/jit/assertionprop.cpp

@@ -2211,6 +2211,22 @@ AssertionInfo Compiler::optAssertionGenJtrue(GenTree* tree)
     // If op1 is lcl and op2 is const or lcl, create assertion.
     if ((op1->gtOper == GT_LCL_VAR) && (op2->OperIsConst() || (op2->gtOper == GT_LCL_VAR))) // Fix for Dev10 851483
     {
+        // Watch out for cases where long local(s) are implicitly truncated.
+        //
+        LclVarDsc* const lcl1Dsc = lvaGetDesc(op1->AsLclVarCommon());
+        if ((lcl1Dsc->TypeGet() == TYP_LONG) && (op1->TypeGet() != TYP_LONG))
+        {
+            return NO_ASSERTION_INDEX;
+        }
+        if (op2->OperIs(GT_LCL_VAR))
+        {
+            LclVarDsc* const lcl2Dsc = lvaGetDesc(op2->AsLclVarCommon());
+            if ((lcl2Dsc->TypeGet() == TYP_LONG) && (op2->TypeGet() != TYP_LONG))
+            {
+                return NO_ASSERTION_INDEX;
+            }
+        }
+
         return optCreateJtrueAssertions(op1, op2, assertionKind);
     }
     else if (!optLocalAssertionProp)

src/tests/JIT/Regression/JitBlue/Runtime_111352/Runtime_111352.cs

@@ -0,0 +1,42 @@
+// 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;
+using Xunit;
+
+public class Runtime_111352
+{
+    [Fact]
+    public static int Test1() => Problem1(0x1_0000_0001L, 0x2_0000_0001L);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    public static int Problem1(long x, long y)
+    {
+        if ((uint)x == (uint)y)
+        {
+            if (x == y)
+            {
+                return -1;
+            }
+        }
+
+        return 100;
+    }
+
+    [Fact]
+    public static int Test2() => Problem2(0x1_0000_0000L);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    public static int Problem2(long x)
+    {
+        if ((uint)x == 0)
+        {
+            if (x == 0)
+            {
+                return -1;
+            }
+        }
+
+        return 100;
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_111352/Runtime_111352.csproj

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