JIT: fix x86 EH issue when removing an empty try (#115731)

Morph may have already cleared out the continuation block, so we won't find
a GT_END_LFIN there.

Fixes #115700

Author: AndyAyersMS

src/coreclr/jit/codegenxarch.cpp

@@ -4879,7 +4879,8 @@ void CodeGen::genCodeForShift(GenTree* tree)
         {
             int shiftByValue = (int)shiftBy->AsIntConCommon()->IconValue();
 
-            if (tree->OperIsRotate() && compiler->compOpportunisticallyDependsOn(InstructionSet_BMI2) && !tree->gtSetFlags())
+            if (tree->OperIsRotate() && compiler->compOpportunisticallyDependsOn(InstructionSet_BMI2) &&
+                !tree->gtSetFlags())
             {
                 // If we have a contained source operand, we must emit rorx.
                 // We may also use rorx for 64bit values when a mov would otherwise be required,
@@ -4906,7 +4907,8 @@ void CodeGen::genCodeForShift(GenTree* tree)
             return;
         }
     }
-    else if (tree->OperIsShift() && compiler->compOpportunisticallyDependsOn(InstructionSet_BMI2) && !tree->gtSetFlags())
+    else if (tree->OperIsShift() && compiler->compOpportunisticallyDependsOn(InstructionSet_BMI2) &&
+             !tree->gtSetFlags())
     {
         // Emit shlx, sarx, shrx if BMI2 is available instead of mov+shl, mov+sar, mov+shr.
         switch (tree->OperGet())

src/coreclr/jit/fgehopt.cpp

@@ -1889,9 +1889,12 @@ void Compiler::fgCleanupContinuation(BasicBlock* continuation)
 
         // Remove the GT_END_LFIN from the continuation,
         // Note we only expect to see one such statement.
+        //
         bool foundEndLFin = false;
+        bool isEmpty      = true;
         for (Statement* const stmt : continuation->Statements())
         {
+            isEmpty       = false;
             GenTree* expr = stmt->GetRootNode();
             if (expr->gtOper == GT_END_LFIN)
             {
@@ -1900,6 +1903,16 @@ void Compiler::fgCleanupContinuation(BasicBlock* continuation)
                 foundEndLFin = true;
             }
         }
+
+        // If the continuation is unreachable, morph may
+        // have changed the continuation to an empty BBJ_THROW.
+        // Tolerate.
+        //
+        if (isEmpty && continuation->KindIs(BBJ_THROW))
+        {
+            return;
+        }
+
         assert(foundEndLFin);
     }
 #endif // FEATURE_EH_WINDOWS_X86

src/coreclr/jit/morph.cpp

@@ -9212,7 +9212,7 @@ GenTree* Compiler::fgOptimizeRelationalComparisonWithConst(GenTreeOp* cmp)
             // LE_UN/GT_UN(expr, int.MaxValue) => EQ/NE(RSZ(expr, 32), 0).
             else if (opts.OptimizationEnabled() && (op1->TypeIs(TYP_LONG) && (op2Value == UINT_MAX)))
             {
-                oper = (oper == GT_GT) ? GT_NE : GT_EQ;
+                oper            = (oper == GT_GT) ? GT_NE : GT_EQ;
                 GenTree* icon32 = gtNewIconNode(32, TYP_INT);
                 icon32->SetMorphed(this);
 

src/tests/JIT/Regression/JitBlue/Runtime_115700/Runtime_115700.cs

@@ -0,0 +1,56 @@
+// Generated by Fuzzlyn v3.0 on 2025-05-18 16:32:05
+// Run on X86 Windows
+// Seed: 16064612445952557242-vectort,vector128,vector256,x86aes,x86avx,x86avx2,x86avx512bw,x86avx512bwvl,x86avx512cd,x86avx512cdvl,x86avx512dq,x86avx512dqvl,x86avx512f,x86avx512fvl,x86bmi1,x86bmi2,x86fma,x86lzcnt,x86pclmulqdq,x86popcnt,x86sse,x86sse2,x86sse3,x86sse41,x86sse42,x86ssse3,x86x86base
+// Reduced from 104.0 KiB to 0.7 KiB in 00:06:27
+// Hits JIT assert in Release:
+// Assertion failed 'foundEndLFin' in 'Program:Main(Fuzzlyn.ExecutionServer.IRuntime)' during 'Remove empty try 2' (IL size 82; hash 0xade6b36b; FullOpts)
+// 
+//     File: D:\a\_work\1\s\src\coreclr\jit\fgehopt.cpp Line: 1903
+// 
+using System;
+using System.Runtime.CompilerServices;
+using Xunit;
+
+public class C0
+{
+    public bool F5;
+    public uint F6;
+}
+
+public class Program
+{
+    public static C0 s_3;
+    public static ushort s_13;
+
+    [Fact]
+    public static void Test()
+    {
+        try 
+        {
+            Problem();
+        }
+        catch (System.Exception)
+        {
+        }
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static void Problem()
+    {
+        C0 vr0 = new C0();
+        try
+        {
+            vr0.F6 = 0;
+        }
+        finally
+        {
+            for (uint vr1 = 0; vr1 < 1; vr1++)
+            {
+                s_13 -= s_13;
+                s_3.F5 |= false;
+                vr0.F5 = vr0.F5 && false;
+                throw new System.Exception();
+            }
+        }
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_115700/Runtime_115700.csproj

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