JIT: Ensure fgTryMorphStructArg morphs created trees (#113496)

In particular we could create `LCL_FLD` or `LCL_VAR` nodes for address
exposed locals without marking them with `GTF_GLOB_REF`. This would
result in not creating some necessary copies.

Author: jakobbotsch

src/coreclr/jit/compiler.h

@@ -6673,7 +6673,7 @@ class Compiler
     GenTree* fgMorphCopyBlock(GenTree* tree);
 private:
     GenTree* fgMorphSmpOp(GenTree* tree, MorphAddrContext* mac, bool* optAssertionPropDone = nullptr);
-    void fgTryReplaceStructLocalWithFields(GenTree** use);
+    bool fgTryReplaceStructLocalWithFields(GenTree** use);
     GenTree* fgMorphFinalizeIndir(GenTreeIndir* indir);
     GenTree* fgOptimizeCast(GenTreeCast* cast);
     GenTree* fgOptimizeCastOnStore(GenTree* store);

src/coreclr/jit/morph.cpp

@@ -2287,6 +2287,7 @@ bool Compiler::fgTryMorphStructArg(CallArg* arg)
 #else
                 *use = fieldList->SoleFieldOrThis();
 #endif
+                *use = fgMorphTree(*use);
             }
             else
             {
@@ -2335,7 +2336,8 @@ bool Compiler::fgTryMorphStructArg(CallArg* arg)
 
         // Try to see if we can use the promoted fields to pass this argument.
         //
-        if (varDsc->lvPromoted && (varDsc->lvFieldCnt == arg->AbiInfo.CountRegsAndStackSlots()))
+        if (varDsc->lvPromoted && !varDsc->lvDoNotEnregister &&
+            (varDsc->lvFieldCnt == arg->AbiInfo.CountRegsAndStackSlots()))
         {
             bool fieldsMatch = true;
 
@@ -2366,6 +2368,7 @@ bool Compiler::fgTryMorphStructArg(CallArg* arg)
             if (fieldsMatch)
             {
                 newArg = fgMorphLclToFieldList(lclNode)->SoleFieldOrThis();
+                newArg = fgMorphTree(newArg);
             }
         }
     }
@@ -2511,7 +2514,7 @@ bool Compiler::fgTryMorphStructArg(CallArg* arg)
                         lvaSetVarDoNotEnregister(lclVar->GetLclNum() DEBUGARG(DoNotEnregisterReason::LocalField));
                     }
                 }
-                result->SetMorphed(this);
+                result = fgMorphTree(result);
                 return result;
             }
             else
@@ -2532,7 +2535,7 @@ bool Compiler::fgTryMorphStructArg(CallArg* arg)
                 }
 
                 GenTree* indir = gtNewIndir(type, addr);
-                indir->SetMorphed(this, /* doChildren*/ true);
+                indir->SetMorphed(this, /* doChildren */ true);
                 return indir;
             }
         };
@@ -2593,16 +2596,15 @@ GenTreeFieldList* Compiler::fgMorphLclToFieldList(GenTreeLclVar* lcl)
     unsigned fieldLclNum = varDsc->lvFieldLclStart;
 
     GenTreeFieldList* fieldList = new (this, GT_FIELD_LIST) GenTreeFieldList();
-    fieldList->SetMorphed(this);
 
     for (unsigned i = 0; i < fieldCount; i++)
     {
         LclVarDsc* fieldVarDsc = lvaGetDesc(fieldLclNum);
         GenTree*   lclVar      = gtNewLclvNode(fieldLclNum, fieldVarDsc->TypeGet());
-        lclVar->SetMorphed(this);
         fieldList->AddField(this, lclVar, fieldVarDsc->lvFldOffset, fieldVarDsc->TypeGet());
         fieldLclNum++;
     }
+
     return fieldList;
 }
 
@@ -8366,7 +8368,10 @@ GenTree* Compiler::fgMorphSmpOp(GenTree* tree, MorphAddrContext* mac, bool* optA
             GenTree*& retVal = tree->AsOp()->ReturnValueRef();
             if ((retVal != nullptr) && ((genReturnBB == nullptr) || (compCurBB == genReturnBB)))
             {
-                fgTryReplaceStructLocalWithFields(&retVal);
+                if (fgTryReplaceStructLocalWithFields(&retVal))
+                {
+                    retVal = fgMorphTree(retVal);
+                }
             }
             break;
         }
@@ -8424,19 +8429,22 @@ GenTree* Compiler::fgMorphSmpOp(GenTree* tree, MorphAddrContext* mac, bool* optA
 // Notes:
 //    Currently only called when the tree parent is a GT_RETURN/GT_SWIFT_ERROR_RET.
 //
-void Compiler::fgTryReplaceStructLocalWithFields(GenTree** use)
+bool Compiler::fgTryReplaceStructLocalWithFields(GenTree** use)
 {
     if (!(*use)->OperIs(GT_LCL_VAR))
     {
-        return;
+        return false;
     }
 
     LclVarDsc* varDsc = lvaGetDesc((*use)->AsLclVar());
 
-    if (!varDsc->lvDoNotEnregister && varDsc->lvPromoted)
+    if (varDsc->lvDoNotEnregister || !varDsc->lvPromoted)
     {
-        *use = fgMorphLclToFieldList((*use)->AsLclVar());
+        return false;
     }
+
+    *use = fgMorphLclToFieldList((*use)->AsLclVar());
+    return true;
 }
 
 //------------------------------------------------------------------------

src/tests/JIT/Regression/JitBlue/Runtime_113488/Runtime_113488.cs

@@ -0,0 +1,41 @@
+// 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 2025-03-13 04:54:06
+// Run on X64 Linux
+// Seed: 15128240988293741626-vectort,vector128,vector256,x86aes,x86avx,x86avx2,x86bmi1,x86bmi1x64,x86bmi2,x86bmi2x64,x86fma,x86lzcnt,x86lzcntx64,x86pclmulqdq,x86popcnt,x86popcntx64,x86sse,x86ssex64,x86sse2,x86sse2x64,x86sse3,x86sse41,x86sse41x64,x86sse42,x86sse42x64,x86ssse3,x86x86base
+// Reduced from 188.7 KiB to 0.8 KiB in 00:01:09
+// Debug: Outputs 0
+// Release: Outputs 1
+using System;
+using System.Numerics;
+using System.Runtime.Intrinsics;
+using System.Runtime.CompilerServices;
+using Xunit;
+
+public class Runtime_113488
+{
+    [Fact]
+    public static int TestEntryPoint()
+    {
+        S0 vr0 = default(S0);
+        return M4(vr0, Vector256.Create<ushort>(vr0.M7()));
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static int M4(S0 arg0, Vector256<ushort> arg1)
+    {
+        return arg0.F0 == 0 ? 100 : 101;
+    }
+    
+    private struct S0
+    {
+        public uint F0;
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        public ushort M7()
+        {
+            this.F0 = 1;
+            return 0;
+        }
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_113488/Runtime_113488.csproj

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