From d11612c2ddaea77556366f060f3e81e787831237 Mon Sep 17 00:00:00 2001
From: Tanner Gooding <tagoo@outlook.com>
Date: Thu, 20 May 2021 15:07:26 -0700
Subject: [PATCH] Ensure ReplaceWithLclVar lowers the created LclVar and
 assignment

---
 src/coreclr/jit/lir.cpp |  7 ++++++-
 src/coreclr/jit/lir.h   |  2 +-
 src/coreclr/jit/lower.h | 11 ++++++++++-
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/coreclr/jit/lir.cpp b/src/coreclr/jit/lir.cpp
index beac0b069e2142..6bcc97b3ea2ea9 100644
--- a/src/coreclr/jit/lir.cpp
+++ b/src/coreclr/jit/lir.cpp
@@ -246,10 +246,11 @@ void LIR::Use::ReplaceWith(Compiler* compiler, GenTree* replacement)
 //    lclNum - The local to use for temporary storage. If BAD_VAR_NUM (the
 //             default) is provided, this method will create and use a new
 //             local var.
+//    assign - On return, if non null, contains the created assignment node
 //
 // Return Value: The number of the local var used for temporary storage.
 //
-unsigned LIR::Use::ReplaceWithLclVar(Compiler* compiler, unsigned lclNum)
+unsigned LIR::Use::ReplaceWithLclVar(Compiler* compiler, unsigned lclNum, GenTree** assign)
 {
     assert(IsInitialized());
     assert(compiler != nullptr);
@@ -277,6 +278,10 @@ unsigned LIR::Use::ReplaceWithLclVar(Compiler* compiler, unsigned lclNum)
     JITDUMP("ReplaceWithLclVar created store :\n");
     DISPNODE(store);
 
+    if (assign != nullptr)
+    {
+        *assign = store;
+    }
     return lclNum;
 }
 
diff --git a/src/coreclr/jit/lir.h b/src/coreclr/jit/lir.h
index 5348b9ed920e9b..e174482be6b36e 100644
--- a/src/coreclr/jit/lir.h
+++ b/src/coreclr/jit/lir.h
@@ -74,7 +74,7 @@ class LIR final
         bool IsDummyUse() const;
 
         void ReplaceWith(Compiler* compiler, GenTree* replacement);
-        unsigned ReplaceWithLclVar(Compiler* compiler, unsigned lclNum = BAD_VAR_NUM);
+        unsigned ReplaceWithLclVar(Compiler* compiler, unsigned lclNum = BAD_VAR_NUM, GenTree** assign = nullptr);
     };
 
     //------------------------------------------------------------------------
diff --git a/src/coreclr/jit/lower.h b/src/coreclr/jit/lower.h
index bc061bf7548f06..7f7c9d3760aa14 100644
--- a/src/coreclr/jit/lower.h
+++ b/src/coreclr/jit/lower.h
@@ -217,9 +217,18 @@ class Lowering final : public Phase
         GenTree* oldUseNode = use.Def();
         if ((oldUseNode->gtOper != GT_LCL_VAR) || (tempNum != BAD_VAR_NUM))
         {
-            use.ReplaceWithLclVar(comp, tempNum);
+            GenTree* assign;
+            use.ReplaceWithLclVar(comp, tempNum, &assign);
+
             GenTree* newUseNode = use.Def();
             ContainCheckRange(oldUseNode->gtNext, newUseNode);
+
+            // We need to lower the LclVar and assignment since there may be certain
+            // types or scenarios, such as TYP_SIMD12, that need special handling
+
+            LowerNode(assign);
+            LowerNode(newUseNode);
+
             return newUseNode->AsLclVar();
         }
         return oldUseNode->AsLclVar();