From f845e3049a515e1cfdc8413f26964e139b5e9272 Mon Sep 17 00:00:00 2001
From: Jakob Botsch Nielsen <jakob.botsch.nielsen@gmail.com>
Date: Mon, 28 Aug 2023 16:10:03 +0200
Subject: [PATCH 1/2] JIT: Fix LowerHWIntrinsicToScalar with unused values

Fix #91173
---
 src/coreclr/jit/lowerxarch.cpp | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/coreclr/jit/lowerxarch.cpp b/src/coreclr/jit/lowerxarch.cpp
index eba7bdb93e20fb..05423024e6df5f 100644
--- a/src/coreclr/jit/lowerxarch.cpp
+++ b/src/coreclr/jit/lowerxarch.cpp
@@ -5314,6 +5314,10 @@ GenTree* Lowering::LowerHWIntrinsicToScalar(GenTreeHWIntrinsic* node)
             {
                 use.ReplaceWith(newIndir);
             }
+            else
+            {
+                newIndir->SetUnusedValue();
+            }
 
             BlockRange().Remove(op1);
             BlockRange().Remove(node);
@@ -5342,6 +5346,10 @@ GenTree* Lowering::LowerHWIntrinsicToScalar(GenTreeHWIntrinsic* node)
                 {
                     use.ReplaceWith(lclFld);
                 }
+                else
+                {
+                    lclFld->SetUnusedValue();
+                }
 
                 BlockRange().Remove(op1);
                 BlockRange().Remove(node);
@@ -5426,6 +5434,11 @@ GenTree* Lowering::LowerHWIntrinsicToScalar(GenTreeHWIntrinsic* node)
         {
             use.ReplaceWith(cast);
         }
+        else
+        {
+            node->ClearUnusedValue();
+            cast->SetUnusedValue();
+        }
         next = LowerNode(cast);
     }
 

From 0e764ae4aa13e6c54a245c2773dcd5469f03e818 Mon Sep 17 00:00:00 2001
From: Jakob Botsch Nielsen <jakob.botsch.nielsen@gmail.com>
Date: Mon, 28 Aug 2023 16:28:10 +0200
Subject: [PATCH 2/2] Fix more cases

---
 src/coreclr/jit/lowerarmarch.cpp |  4 ++++
 src/coreclr/jit/lowerxarch.cpp   | 32 ++++++++++++++++++++++++++++++--
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/src/coreclr/jit/lowerarmarch.cpp b/src/coreclr/jit/lowerarmarch.cpp
index 86a5b2b1ab4cb4..2536d44aa00c56 100644
--- a/src/coreclr/jit/lowerarmarch.cpp
+++ b/src/coreclr/jit/lowerarmarch.cpp
@@ -1900,6 +1900,10 @@ GenTree* Lowering::LowerHWIntrinsicDot(GenTreeHWIntrinsic* node)
     {
         use.ReplaceWith(tmp2);
     }
+    else
+    {
+        tmp2->SetUnusedValue();
+    }
 
     BlockRange().Remove(node);
     return tmp2->gtNext;
diff --git a/src/coreclr/jit/lowerxarch.cpp b/src/coreclr/jit/lowerxarch.cpp
index 05423024e6df5f..c1b5079f124545 100644
--- a/src/coreclr/jit/lowerxarch.cpp
+++ b/src/coreclr/jit/lowerxarch.cpp
@@ -3868,6 +3868,10 @@ GenTree* Lowering::LowerHWIntrinsicGetElement(GenTreeHWIntrinsic* node)
         {
             use.ReplaceWith(newIndir);
         }
+        else
+        {
+            newIndir->SetUnusedValue();
+        }
 
         BlockRange().Remove(op1);
         BlockRange().Remove(node);
@@ -3916,6 +3920,10 @@ GenTree* Lowering::LowerHWIntrinsicGetElement(GenTreeHWIntrinsic* node)
                 {
                     use.ReplaceWith(lclFld);
                 }
+                else
+                {
+                    lclFld->SetUnusedValue();
+                }
 
                 BlockRange().Remove(op1);
                 BlockRange().Remove(op2);
@@ -4158,6 +4166,11 @@ GenTree* Lowering::LowerHWIntrinsicGetElement(GenTreeHWIntrinsic* node)
         {
             use.ReplaceWith(cast);
         }
+        else
+        {
+            node->ClearUnusedValue();
+            cast->SetUnusedValue();
+        }
         next = LowerNode(cast);
     }
 
@@ -4737,6 +4750,10 @@ GenTree* Lowering::LowerHWIntrinsicDot(GenTreeHWIntrinsic* node)
                 {
                     use.ReplaceWith(tmp1);
                 }
+                else
+                {
+                    tmp1->SetUnusedValue();
+                }
 
                 BlockRange().Remove(node);
                 return LowerNode(tmp1);
@@ -5267,6 +5284,10 @@ GenTree* Lowering::LowerHWIntrinsicDot(GenTreeHWIntrinsic* node)
     {
         use.ReplaceWith(tmp1);
     }
+    else
+    {
+        tmp1->SetUnusedValue();
+    }
 
     BlockRange().Remove(node);
     return tmp1->gtNext;
@@ -8345,8 +8366,15 @@ void Lowering::TryFoldCnsVecForEmbeddedBroadcast(GenTreeHWIntrinsic* parentNode,
         BlockRange().InsertBefore(broadcastNode, createScalar);
         BlockRange().InsertBefore(createScalar, constScalar);
         LIR::Use use;
-        BlockRange().TryGetUse(childNode, &use);
-        use.ReplaceWith(broadcastNode);
+        if (BlockRange().TryGetUse(childNode, &use))
+        {
+            use.ReplaceWith(broadcastNode);
+        }
+        else
+        {
+            broadcastNode->SetUnusedValue();
+        }
+
         BlockRange().Remove(childNode);
         LowerNode(createScalar);
         LowerNode(broadcastNode);