Fix typing of BlendVariableMask condition when optimizing TernaryLogic

src/coreclr/jit/lowerxarch.cpp

@@ -3875,6 +3875,20 @@ GenTree* Lowering::LowerHWIntrinsicTernaryLogic(GenTreeHWIntrinsic* node)
                 }
 
                 assert(varTypeIsMask(condition));
+
+                // The TernaryLogic node normalizes small SIMD base types on import. To optimize
+                // to BlendVariableMask, we need to "un-normalize". We no longer have the original
+                // base type, so we use the mask base type instead.
+                NamedIntrinsic intrinsicId = node->GetHWIntrinsicId();
+                assert(HWIntrinsicInfo::NeedsNormalizeSmallTypeToInt(intrinsicId));
+
+                if (!condition->OperIsHWIntrinsic())
+                {
+                    break;
+                }
+
+                node->SetSimdBaseJitType(condition->AsHWIntrinsic()->GetSimdBaseJitType());
+
                 node->ResetHWIntrinsicId(NI_EVEX_BlendVariableMask, comp, selectFalse, selectTrue, condition);
                 BlockRange().Remove(op4);
                 break;

src/tests/JIT/Regression/JitBlue/Runtime_114572/Runtime_114572.cs

@@ -0,0 +1,72 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+//
+// Generated by Fuzzlyn v2.5 on 2025-04-11 19:29:41
+// Run on X64 Windows
+// Seed: 557319528607462789-vectort,vector128,vector256,x86aes,x86avx,x86avx2,x86avx512bw,x86avx512bwvl,x86avx512cd,x86avx512cdvl,x86avx512dq,x86avx512dqvl,x86avx512f,x86avx512fvl,x86avx512fx64,x86bmi1,x86bmi1x64,x86bmi2,x86bmi2x64,x86fma,x86lzcnt,x86lzcntx64,x86pclmulqdq,x86popcnt,x86popcntx64,x86sse,x86ssex64,x86sse2,x86sse2x64,x86sse3,x86sse41,x86sse41x64,x86sse42,x86sse42x64,x86ssse3,x86x86base
+// Reduced from 41.1 KiB to 0.7 KiB in 00:01:23
+// Debug: Outputs <0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1>
+// Release: Outputs <0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1>
+
+using System;
+using System.Numerics;
+using System.Runtime.Intrinsics;
+using System.Runtime.Intrinsics.X86;
+using Xunit;
+
+public class Runtime_114572
+{
+    public static Vector256<ushort> s_2;
+    public static ushort s_4;
+    public static byte s_ub = 1;
+    public static ushort s_us = 1;
+
+    [Fact]
+    public static void Problem()
+    {
+        if (Avx512F.VL.IsSupported)
+        {
+            var vr11 = Vector256.Create<ushort>(0);
+            var vr12 = Vector256.Create<ushort>(1);
+            var vr13 = (ushort)0;
+            var vr14 = Vector256.CreateScalar(vr13);
+            var vr15 = (ushort)1;
+            var vr16 = Vector256.CreateScalar(vr15);
+            var vr17 = Vector256.Create<ushort>(s_4);
+            var vr18 = Avx2.Max(vr16, vr17);
+            s_2 = Avx512F.VL.TernaryLogic(vr11, vr12, Avx512BW.VL.CompareGreaterThanOrEqual(vr14, vr18), 216);
+            System.Console.WriteLine(s_2);
+            Assert.Equal(Vector256.Create((ushort)0, (ushort)1, (ushort)1, (ushort)1, (ushort)1, (ushort)1, (ushort)1, (ushort)1, (ushort)1, (ushort)1, (ushort)1, (ushort)1, (ushort)1, (ushort)1, (ushort)1, (ushort)1), s_2);
+        }
+    }
+
+    [Fact]
+    public static void Problem2()
+    {
+        if (Avx512F.VL.IsSupported)
+        {
+            var v0 = Vector128<ushort>.Zero;
+            var v1 = Vector128<ushort>.One;
+            var vs = Vector128.CreateScalar(s_us);
+
+            var vr = Avx512F.VL.TernaryLogic(v0, v1, Avx512BW.VL.CompareGreaterThanOrEqual(v0, vs), 0xE4);
+            Console.WriteLine(vr);
+            Assert.Equal(Vector128.Create((ushort)1, (ushort)0, (ushort)0, (ushort)0, (ushort)0, (ushort)0, (ushort)0, (ushort)0), vr);
+        }
+    }
+
+    [Fact]
+    public static void Problem3()
+    {
+        if (Avx512F.VL.IsSupported)
+        {
+            var v0 = Vector128<byte>.Zero;
+            var v1 = Vector128<byte>.One;
+            var vs = Vector128.CreateScalar(s_ub);
+
+            var vr = Avx512F.VL.TernaryLogic(v0, v1, Avx512BW.VL.CompareGreaterThanOrEqual(v0, vs), 0xE4);
+            Console.WriteLine(vr);
+            Assert.Equal(Vector128.Create((byte)1, (byte)0, (byte)0, (byte)0, (byte)0, (byte)0, (byte)0, (byte)0, (byte)0, (byte)0, (byte)0, (byte)0, (byte)0, (byte)0, (byte)0, (byte)0), vr);
+        }
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_114572/Runtime_114572.csproj

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