[RyuJIT] Don't optimize "x < 0" to shift for unsigned cmp

src/coreclr/jit/codegenxarch.cpp

@@ -5955,29 +5955,28 @@ void CodeGen::genCompareInt(GenTree* treeNode)
     }
     else if (op1->isUsedFromReg() && op2->IsIntegralConst(0))
     {
-        emitAttr targetSize = emitActualTypeSize(op1->TypeGet());
-        emitAttr op1Size    = emitActualTypeSize(op1->TypeGet());
-
-        // Optimize "x<0" and "x>=0" to "x>>31" if "x" is not a jump condition and in a reg.
-        // Morph/Lowering are responsible to rotate "0<x" to "x>0" so we won't handle it here.
-        if ((targetSize >= 4) && (op1Size >= 4) && (targetReg != REG_NA) && tree->OperIs(GT_LT, GT_GE))
+        if (compiler->opts.OptimizationEnabled())
         {
-            if (targetReg != op1->GetRegNum())
-            {
-                inst_RV_RV(INS_mov, targetReg, op1->GetRegNum(), op1->TypeGet());
-            }
-            if (tree->OperIs(GT_GE))
+            emitAttr op1Size = emitActualTypeSize(op1->TypeGet());
+            assert((int)op1Size >= 4);
+
+            // Optimize "x<0" and "x>=0" to "x>>31" if "x" is not a jump condition and in a reg.
+            // Morph/Lowering are responsible to rotate "0<x" to "x>0" so we won't handle it here.
+            if ((targetReg != REG_NA) && tree->OperIs(GT_LT, GT_GE) && !tree->IsUnsigned())
             {
-                // emit "not" for "x>=0" case
-                inst_RV(INS_not, targetReg, tree->TypeGet(), op1Size);
+                if (targetReg != op1->GetRegNum())
+                {
+                    inst_RV_RV(INS_mov, targetReg, op1->GetRegNum(), op1->TypeGet());
+                }
+                if (tree->OperIs(GT_GE))
+                {
+                    // emit "not" for "x>=0" case
+                    inst_RV(INS_not, targetReg, op1->TypeGet());
+                }
+                inst_RV_IV(INS_shr_N, targetReg, (int)op1Size * 8 - 1, op1Size);
+                genProduceReg(tree);
+                return;
             }
-            inst_RV_IV(INS_shr_N, targetReg, (int)op1Size * 8 - 1, op1Size);
-            genProduceReg(tree);
-            return;
-        }
-
-        if (compiler->opts.OptimizationEnabled())
-        {
             canReuseFlags = true;
         }
 

src/libraries/Microsoft.CSharp/tests/IntegerBinaryOperationTests.cs

@@ -498,7 +498,6 @@ public void RuntimeExpression(object x, object y, ExpressionType type, object re
         [MemberData(nameof(UInt64TestNotEquals))]
         [MemberData(nameof(UInt64TestSubtractions))]
         [ActiveIssue("https://github.com/dotnet/runtime/issues/26798", TargetFrameworkMonikers.NetFramework)]
-        [SkipOnCoreClr("https://github.com/dotnet/runtime/issues/42719", RuntimeConfiguration.Checked)]
         public void ConstantExpressions(object x, object y, ExpressionType type, object result, bool shouldSucceedChecked)
         {
             var callsite = GetBinaryOperationCallSite(type, false, true, true);

src/tests/JIT/opt/JitMinOpts/Regression/GitHub_42719.il

@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+.assembly extern mscorlib { }
+.assembly GitHub_42719 {}
+.module GitHub_42719.exe
+.method public static int32 Main() cil managed
+{
+    .entrypoint
+    .maxstack  5
+    // "0 u> -1" shouldn't be optimized into "-1 >> 31"
+    ldc.i4.s   100
+    ldc.i4.0
+    ldc.i4.m1
+    cgt.un
+    add  
+    ret
+}

src/tests/JIT/opt/JitMinOpts/Regression/GitHub_42719.ilproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk.IL">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <Optimize>False</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="GitHub_42719.il" />
+  </ItemGroup>
+</Project>

src/tests/JIT/opt/JitMinOpts/Regression/GitHub_42719_opt.ilproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk.IL">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <Optimize>True</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="GitHub_42719.il" />
+  </ItemGroup>
+</Project>