JIT: Handle edge cases around BlendVariableMask rewrite

src/coreclr/jit/rationalize.cpp

@@ -638,7 +638,8 @@ void Rationalizer::RewriteHWIntrinsicBlendv(GenTree** use, Compiler::GenTreeStac
         return;
     }
 
-    GenTree* op2 = node->Op(2);
+    GenTree*  op2 = node->Op(2);
+    GenTree*& op3 = node->Op(3);
 
     // We're in the post-order visit and are traversing in execution order, so
     // everything between op2 and node will have already been rewritten to LIR
@@ -648,7 +649,16 @@ void Rationalizer::RewriteHWIntrinsicBlendv(GenTree** use, Compiler::GenTreeStac
     // variant
     SideEffectSet scratchSideEffects;
 
-    if (scratchSideEffects.IsLirInvariantInRange(m_compiler, op2, node))
+    // If the mask was originally a vector, we don't want to create a mask solely for
+    // the purpose of embedding it. vpmov*2m is relatively costly compared to blendvp*.
+    bool isVectorToMask          = op3->OperIsConvertVectorToMask();
+    bool isVectorBlendCompatible = true;
+
+    if (isVectorToMask)
+    {
+        isVectorBlendCompatible = varTypeIsFloating(simdBaseType) || varTypeIsByte(simdBaseType);
+    }
+    else if (scratchSideEffects.IsLirInvariantInRange(m_compiler, op2, node))
     {
         unsigned  tgtMaskSize     = simdSize / genTypeSize(simdBaseType);
         var_types tgtSimdBaseType = TYP_UNDEF;
@@ -667,9 +677,7 @@ void Rationalizer::RewriteHWIntrinsicBlendv(GenTree** use, Compiler::GenTreeStac
         }
     }
 
-    GenTree*& op3 = node->Op(3);
-
-    if (!ShouldRewriteToNonMaskHWIntrinsic(op3))
+    if (!isVectorBlendCompatible || !ShouldRewriteToNonMaskHWIntrinsic(op3))
     {
         return;
     }

src/tests/JIT/Regression/JitBlue/Runtime_127260/Runtime_127260.cs

@@ -0,0 +1,149 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+using System.Runtime.Intrinsics.X86;
+using Xunit;
+
+public class Runtime_127260
+{
+    [ConditionalFact(typeof(Sse41), nameof(Sse41.IsSupported))]
+    public static void TestBlendVariable()
+    {
+        Assert.Equal(Vector128<float>.Zero,
+            BlendVariableSse41Single(Vector128.Create(-1.0f), Vector128<float>.Zero, Vector128.Create(-0.0f)));
+
+        Assert.Equal(Vector128<double>.Zero,
+            BlendVariableSse41Double(Vector128.Create(-1.0), Vector128<double>.Zero, Vector128.Create(-0.0)));
+
+        Assert.Equal(Vector128<sbyte>.Zero,
+            BlendVariableSse41Int8(Vector128.Create<sbyte>(-1), Vector128<sbyte>.Zero, Vector128.Create(sbyte.MinValue)));
+
+        Assert.Equal(Vector128.Create<short>(0x00FF),
+            BlendVariableSse41Int16(Vector128.Create<short>(-1), Vector128<short>.Zero, Vector128.Create(short.MinValue)));
+
+        Assert.Equal(Vector128.Create<int>(0x00FFFFFF),
+            BlendVariableSse41Int32(Vector128.Create<int>(-1), Vector128<int>.Zero, Vector128.Create(int.MinValue)));
+
+        Assert.Equal(Vector128.Create<long>(0x00FFFFFF_FFFFFFFF),
+            BlendVariableSse41Int64(Vector128.Create<long>(-1), Vector128<long>.Zero, Vector128.Create(long.MinValue)));
+    }
+
+    [ConditionalFact(typeof(Avx512BW.VL), nameof(Avx512BW.VL.IsSupported))]
+    public static void TestBlendVariableMask()
+    {
+        Assert.Equal(Vector128<float>.Zero,
+            BlendVariableAvx512Single(Vector128.Create(-1.0f), Vector128<float>.Zero, Vector128.Create(-0.0f)));
+
+        Assert.Equal(Vector128<double>.Zero,
+            BlendVariableAvx512Double(Vector128.Create(-1.0), Vector128<double>.Zero, Vector128.Create(-0.0)));
+
+        Assert.Equal(Vector128<sbyte>.Zero,
+            BlendVariableAvx512Int8(Vector128.Create<sbyte>(-1), Vector128<sbyte>.Zero, Vector128.Create(sbyte.MinValue)));
+
+        Assert.Equal(Vector128<short>.Zero,
+            BlendVariableAvx512Int16(Vector128.Create<short>(-1), Vector128<short>.Zero, Vector128.Create(short.MinValue)));
+
+        Assert.Equal(Vector128<int>.Zero,
+            BlendVariableAvx512Int32(Vector128.Create<int>(-1), Vector128<int>.Zero, Vector128.Create(int.MinValue)));
+
+        Assert.Equal(Vector128<long>.Zero,
+            BlendVariableAvx512Int64(Vector128.Create<long>(-1), Vector128<long>.Zero, Vector128.Create(long.MinValue)));
+    }
+
+    [ConditionalFact(typeof(Avx512BW.VL), nameof(Avx512BW.VL.IsSupported))]
+    public static void TestContainableMask()
+    {
+        Assert.Equal(Vector128<float>.Zero,
+            AddToNegativeSingle(Vector128.Create(-1.0f), Vector128<float>.One));
+
+        Assert.Equal(Vector128<double>.Zero,
+            AddToNegativeDouble(Vector128.Create(-1.0), Vector128<double>.One));
+
+        Assert.Equal(Vector128<sbyte>.Zero,
+            AddToNegativeInt8(Vector128.Create<sbyte>(-1), Vector128<sbyte>.One));
+
+        Assert.Equal(Vector128<short>.Zero,
+            AddToNegativeInt16(Vector128.Create<short>(-1), Vector128<short>.One));
+
+        Assert.Equal(Vector128<int>.Zero,
+            AddToNegativeInt32(Vector128.Create<int>(-1), Vector128<int>.One));
+
+        Assert.Equal(Vector128<long>.Zero,
+            AddToNegativeInt64(Vector128.Create<long>(-1), Vector128<long>.One));
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static Vector128<float> BlendVariableSse41Single(Vector128<float> left, Vector128<float> right, Vector128<float> mask)
+        => Sse41.BlendVariable(left, right, mask);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static Vector128<double> BlendVariableSse41Double(Vector128<double> left, Vector128<double> right, Vector128<double> mask)
+        => Sse41.BlendVariable(left, right, mask);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static Vector128<sbyte> BlendVariableSse41Int8(Vector128<sbyte> left, Vector128<sbyte> right, Vector128<sbyte> mask)
+        => Sse41.BlendVariable(left, right, mask);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static Vector128<short> BlendVariableSse41Int16(Vector128<short> left, Vector128<short> right, Vector128<short> mask)
+        => Sse41.BlendVariable(left, right, mask);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static Vector128<int> BlendVariableSse41Int32(Vector128<int> left, Vector128<int> right, Vector128<int> mask)
+        => Sse41.BlendVariable(left, right, mask);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static Vector128<long> BlendVariableSse41Int64(Vector128<long> left, Vector128<long> right, Vector128<long> mask)
+        => Sse41.BlendVariable(left, right, mask);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static Vector128<float> BlendVariableAvx512Single(Vector128<float> left, Vector128<float> right, Vector128<float> mask)
+        => Avx512F.VL.BlendVariable(left, right, mask);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static Vector128<double> BlendVariableAvx512Double(Vector128<double> left, Vector128<double> right, Vector128<double> mask)
+        => Avx512F.VL.BlendVariable(left, right, mask);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static Vector128<sbyte> BlendVariableAvx512Int8(Vector128<sbyte> left, Vector128<sbyte> right, Vector128<sbyte> mask)
+        => Avx512BW.VL.BlendVariable(left, right, mask);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static Vector128<short> BlendVariableAvx512Int16(Vector128<short> left, Vector128<short> right, Vector128<short> mask)
+        => Avx512BW.VL.BlendVariable(left, right, mask);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static Vector128<int> BlendVariableAvx512Int32(Vector128<int> left, Vector128<int> right, Vector128<int> mask)
+        => Avx512F.VL.BlendVariable(left, right, mask);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static Vector128<long> BlendVariableAvx512Int64(Vector128<long> left, Vector128<long> right, Vector128<long> mask)
+        => Avx512F.VL.BlendVariable(left, right, mask);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static Vector128<float> AddToNegativeSingle(Vector128<float> left, Vector128<float> right)
+        => Sse41.BlendVariable(left, left + right, left);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static Vector128<double> AddToNegativeDouble(Vector128<double> left, Vector128<double> right)
+        => Sse41.BlendVariable(left, left + right, left);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static Vector128<sbyte> AddToNegativeInt8(Vector128<sbyte> left, Vector128<sbyte> right)
+        => Sse41.BlendVariable(left, left + right, left);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static Vector128<short> AddToNegativeInt16(Vector128<short> left, Vector128<short> right)
+        => Avx512BW.VL.BlendVariable(left, left + right, left);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static Vector128<int> AddToNegativeInt32(Vector128<int> left, Vector128<int> right)
+        => Avx512F.VL.BlendVariable(left, left + right, left);
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    static Vector128<long> AddToNegativeInt64(Vector128<long> left, Vector128<long> right)
+        => Avx512F.VL.BlendVariable(left, left + right, left);
+}

src/tests/JIT/Regression/Regression_ro_2.csproj

@@ -95,6 +95,7 @@
     <Compile Include="JitBlue\Runtime_125301\Runtime_125301.cs" />
     <Compile Include="JitBlue\Runtime_125328\Runtime_125328.cs" />
     <Compile Include="JitBlue\Runtime_126060\Runtime_126060.cs" />
+    <Compile Include="JitBlue\Runtime_127260\Runtime_127260.cs" />
   </ItemGroup>
   <Import Project="$(TestSourceDir)MergedTestRunner.targets" />
 </Project>