Add and use a MakeSrcRegOptional that validates IsSafeToContainMem was called

src/coreclr/jit/lower.cpp

@@ -40,6 +40,7 @@ void Lowering::MakeSrcContained(GenTree* parentNode, GenTree* childNode) const
 {
     assert(!parentNode->OperIsLeaf());
     assert(childNode->canBeContained());
+
     childNode->SetContained();
     assert(childNode->isContained());
 
@@ -60,6 +61,34 @@ void Lowering::MakeSrcContained(GenTree* parentNode, GenTree* childNode) const
 #endif
 }
 
+//------------------------------------------------------------------------
+// MakeSrcRegOptional: Make "childNode" a regOptional node
+//
+// Arguments:
+//    parentNode - is a non-leaf node that can regOptional its 'childNode'
+//    childNode  - is an op that will now be regOptional to its parent.
+//
+void Lowering::MakeSrcRegOptional(GenTree* parentNode, GenTree* childNode) const
+{
+    assert(!parentNode->OperIsLeaf());
+
+    childNode->SetRegOptional();
+    assert(childNode->IsRegOptional());
+
+#ifdef DEBUG
+    // Verify caller of this method checked safety.
+    //
+    const bool isSafeToContainMem = IsSafeToContainMem(parentNode, childNode);
+
+    if (!isSafeToContainMem)
+    {
+        JITDUMP("** Unsafe regOptional of [%06u] in [%06u}\n", comp->dspTreeID(childNode),
+                comp->dspTreeID(parentNode));
+        assert(isSafeToContainMem);
+    }
+#endif
+}
+
 //------------------------------------------------------------------------
 // CheckImmedAndMakeContained: Checks if the 'childNode' is a containable immediate
 //    and, if so, makes it contained.

src/coreclr/jit/lower.h

@@ -288,6 +288,7 @@ class Lowering final : public Phase
         const bool op2Legal = isSafeToMarkOp2 && (operatorSize == genTypeSize(op2->TypeGet()));
 
         GenTree* regOptionalOperand = nullptr;
+
         if (op1Legal)
         {
             regOptionalOperand = op2Legal ? PreferredRegOptionalOperand(tree) : op1;
@@ -296,9 +297,10 @@ class Lowering final : public Phase
         {
             regOptionalOperand = op2;
         }
+
         if (regOptionalOperand != nullptr)
         {
-            regOptionalOperand->SetRegOptional();
+            MakeSrcRegOptional(tree, regOptionalOperand);
         }
     }
 #endif // defined(TARGET_XARCH)
@@ -447,7 +449,7 @@ class Lowering final : public Phase
     bool IsContainableBinaryOp(GenTree* parentNode, GenTree* childNode) const;
 #endif // TARGET_ARM64
 
-#ifdef FEATURE_HW_INTRINSICS
+#if defined(FEATURE_HW_INTRINSICS)
     // Tries to get a containable node for a given HWIntrinsic
     bool TryGetContainableHWIntrinsicOp(GenTreeHWIntrinsic* containingNode,
                                         GenTree**           pNode,
@@ -465,6 +467,37 @@ class Lowering final : public Phase
     // Makes 'childNode' contained in the 'parentNode'
     void MakeSrcContained(GenTree* parentNode, GenTree* childNode) const;
 
+    // Makes 'childNode' regOptional in the 'parentNode'
+    void MakeSrcRegOptional(GenTree* parentNode, GenTree* childNode) const;
+
+    // Tries to make 'childNode' contained or regOptional in the 'parentNode'
+    inline void TryMakeSrcContainedOrRegOptional(GenTree* parentNode, GenTree* childNode) const
+    {
+#if defined(FEATURE_HW_INTRINSICS)
+        // HWIntrinsic nodes should use TryGetContainableHWIntrinsicOp and its relevant handling
+        assert(!parentNode->OperIsHWIntrinsic());
+#endif
+
+        if (!IsSafeToContainMem(parentNode, childNode))
+        {
+            return;
+        }
+
+        if (IsContainableMemoryOp(childNode))
+        {
+            MakeSrcContained(parentNode, childNode);
+        }
+        else
+        {
+            MakeSrcRegOptional(parentNode, childNode);
+        }
+    }
+
+#if defined(FEATURE_HW_INTRINSICS)
+    // Tries to make 'childNode' contained or regOptional in the 'parentNode'
+    void TryMakeSrcContainedOrRegOptional(GenTreeHWIntrinsic* parentNode, GenTree* childNode) const;
+#endif
+
     // Checks and makes 'childNode' contained in the 'parentNode'
     bool CheckImmedAndMakeContained(GenTree* parentNode, GenTree* childNode);