Don't map P-DEP SIMD12 local vars to SIMD16 on x64

P-DEP local vars are logically independent locals, but physically embeded
in some structure with fixed layout. So they cannot be made larger.

We already had safeguards for ths in place for x86 so extend these to kick
in for x64 too.

Also update Lowering's checker to account for the fact that some SIMD12s
can persist in x64.

Fixes #12950.

src/jit/compiler.h

@@ -2744,12 +2744,11 @@ class Compiler
 
 #if defined(_TARGET_64BIT_)
         assert(varDsc->lvSize() == 16);
-        return true;
-#else // !defined(_TARGET_64BIT_)
+#endif // defined(_TARGET_64BIT_)
 
-        // For 32-bit architectures, we make local variable SIMD12 types 16 bytes instead of just 12. lvSize()
+        // We make local variable SIMD12 types 16 bytes instead of just 12. lvSize()
         // already does this calculation. However, we also need to prevent mapping types if the var is a
-        // depenendently promoted struct field, which must remain its exact size within its parent struct.
+        // dependently promoted struct field, which must remain its exact size within its parent struct.
         // However, we don't know this until late, so we may have already pretended the field is bigger
         // before that.
         if ((varDsc->lvSize() == 16) && !lvaIsFieldOfDependentlyPromotedStruct(varDsc))
@@ -2760,8 +2759,6 @@ class Compiler
         {
             return false;
         }
-
-#endif // !defined(_TARGET_64BIT_)
     }
 #endif // defined(FEATURE_SIMD)
 

src/jit/lower.cpp

@@ -4656,9 +4656,10 @@ void Lowering::CheckCall(GenTreeCall* call)
 //                      after lowering.
 //
 // Arguments:
+//   compiler - the compiler context.
 //   node - the node to check.
 //
-void Lowering::CheckNode(GenTree* node)
+void Lowering::CheckNode(Compiler* compiler, GenTree* node)
 {
     switch (node->OperGet())
     {
@@ -4668,13 +4669,19 @@ void Lowering::CheckNode(GenTree* node)
 
 #ifdef FEATURE_SIMD
         case GT_SIMD:
+            assert(node->TypeGet() != TYP_SIMD12);
+            break;
 #ifdef _TARGET_64BIT_
         case GT_LCL_VAR:
         case GT_STORE_LCL_VAR:
+        {
+            unsigned   lclNum = node->AsLclVarCommon()->GetLclNum();
+            LclVarDsc* lclVar = &compiler->lvaTable[lclNum];
+            assert(node->TypeGet() != TYP_SIMD12 || compiler->lvaIsFieldOfDependentlyPromotedStruct(lclVar));
+        }
+        break;
 #endif // _TARGET_64BIT_
-            assert(node->TypeGet() != TYP_SIMD12);
-            break;
-#endif
+#endif // SIMD
 
         default:
             break;
@@ -4696,7 +4703,7 @@ bool Lowering::CheckBlock(Compiler* compiler, BasicBlock* block)
     LIR::Range& blockRange = LIR::AsRange(block);
     for (GenTree* node : blockRange)
     {
-        CheckNode(node);
+        CheckNode(compiler, node);
     }
 
     assert(blockRange.CheckLIR(compiler));

src/jit/lower.h

@@ -51,7 +51,7 @@ class Lowering : public Phase
 #ifdef DEBUG
     static void CheckCallArg(GenTree* arg);
     static void CheckCall(GenTreeCall* call);
-    static void CheckNode(GenTree* node);
+    static void CheckNode(Compiler* compiler, GenTree* node);
     static bool CheckBlock(Compiler* compiler, BasicBlock* block);
 #endif // DEBUG
 

tests/src/JIT/Regression/JitBlue/GitHub_12950/GitHub_12950.cs

@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Numerics;
+
+class Program
+{
+    struct BoundingBoxTest
+    {
+        public Vector3 Min;
+        public Vector3 Max;
+
+        public override int GetHashCode()
+        {
+            return Min.GetHashCode() + Max.GetHashCode();
+        }
+    }
+
+    public static void Test()
+    {
+        var box = new BoundingBoxTest();
+        box.Min = Vector3.Min(box.Min, box.Min);
+        var hmm = box.GetHashCode();
+    }
+
+    static int Main(string[] args)
+    {
+        var someMemory = new int[1];
+        var someMoreMemory = new int[1];
+        Test();
+        someMoreMemory[someMemory[0]] = 100;
+        return someMoreMemory[0];
+    }
+}

tests/src/JIT/Regression/JitBlue/GitHub_12950/GitHub_12950.csproj

@@ -0,0 +1,38 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="12.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.props))\dir.props" />
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
+    <AssemblyName>$(MSBuildProjectName)</AssemblyName>
+    <SchemaVersion>2.0</SchemaVersion>
+    <ProjectGuid>{95DFC527-4DC1-495E-97D7-E94EE1F7140D}</ProjectGuid>
+    <OutputType>Exe</OutputType>
+    <ProjectTypeGuids>{786C830F-07A1-408B-BD7F-6EE04809D6DB};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
+    <SolutionDir Condition="$(SolutionDir) == '' Or $(SolutionDir) == '*Undefined*'">..\..\</SolutionDir>
+
+  </PropertyGroup>
+  <!-- Default configurations to help VS understand the configurations -->
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
+  </PropertyGroup>
+  <ItemGroup>
+    <CodeAnalysisDependentAssemblyPaths Condition=" '$(VS100COMNTOOLS)' != '' " Include="$(VS100COMNTOOLS)..\IDE\PrivateAssemblies">
+      <Visible>False</Visible>
+    </CodeAnalysisDependentAssemblyPaths>
+  </ItemGroup>
+  <PropertyGroup>
+    <DebugType></DebugType>
+    <Optimize>True</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+  <ItemGroup>
+    <Service Include="{82A7F48D-3B50-4B1E-B82E-3ADA8210C358}" />
+  </ItemGroup>
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.targets))\dir.targets" />
+  <PropertyGroup Condition=" '$(MsBuildProjectDirOverride)' != '' ">
+  </PropertyGroup> 
+</Project>