Start generating LCL_FLDs in LocalAddressVisitor (dotnet#737)

* Start generating LCL_FLDs in LocalAddressVisitor

* Fix broken vararg offset computation

Since it's subtracted the local field offset also need to be subtracted so it actually ends up being added as needed.

* Introduce array/index temps for LCL_FLDs

Previously fgMorphArrayIndex was always creating temporaries for array/index FIELD trees. Since now LCL_FLDs are created before fgMorphArrayIndex this preserves the existing behavior.

* CR feedback

* Fix incorrect field sequence type check

* Fix GetTail formatting

src/coreclr/src/jit/compiler.h

@@ -7955,6 +7955,7 @@ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
 
     void setLclRelatedToSIMDIntrinsic(GenTree* tree);
     bool areFieldsContiguous(GenTree* op1, GenTree* op2);
+    bool areLocalFieldsContiguous(GenTreeLclFld* first, GenTreeLclFld* second);
     bool areArrayElementsContiguous(GenTree* op1, GenTree* op2);
     bool areArgumentsContiguous(GenTree* op1, GenTree* op2);
     GenTree* createAddressNodeForSIMDInit(GenTree* tree, unsigned simdSize);

src/coreclr/src/jit/gentree.cpp

@@ -18009,7 +18009,7 @@ bool FieldSeqNode::IsConstantIndexFieldSeq()
     return m_fieldHnd == FieldSeqStore::ConstantIndexPseudoField;
 }
 
-bool FieldSeqNode::IsPseudoField()
+bool FieldSeqNode::IsPseudoField() const
 {
     return m_fieldHnd == FieldSeqStore::FirstElemPseudoField || m_fieldHnd == FieldSeqStore::ConstantIndexPseudoField;
 }

src/coreclr/src/jit/gentree.h

@@ -235,7 +235,23 @@ struct FieldSeqNode
     bool IsConstantIndexFieldSeq();
 
     // returns true when this is the the pseudo #FirstElem field sequence or the pseudo #ConstantIndex field sequence
-    bool IsPseudoField();
+    bool IsPseudoField() const;
+
+    CORINFO_FIELD_HANDLE GetFieldHandle() const
+    {
+        assert(!IsPseudoField() && (m_fieldHnd != nullptr));
+        return m_fieldHnd;
+    }
+
+    FieldSeqNode* GetTail()
+    {
+        FieldSeqNode* tail = this;
+        while (tail->m_next != nullptr)
+        {
+            tail = tail->m_next;
+        }
+        return tail;
+    }
 
     // Make sure this provides methods that allow it to be used as a KeyFuncs type in SimplerHash.
     static int GetHashCode(FieldSeqNode fsn)
@@ -3244,6 +3260,13 @@ struct GenTreeField : public GenTree
         gtFieldLookup.addr = nullptr;
 #endif
     }
+
+    // True if this field is a volatile memory operation.
+    bool IsVolatile() const
+    {
+        return (gtFlags & GTF_FLD_VOLATILE) != 0;
+    }
+
 #if DEBUGGABLE_GENTREE
     GenTreeField() : GenTree()
     {
@@ -5038,6 +5061,18 @@ struct GenTreeIndir : public GenTreeOp
     {
     }
 
+    // True if this indirection is a volatile memory operation.
+    bool IsVolatile() const
+    {
+        return (gtFlags & GTF_IND_VOLATILE) != 0;
+    }
+
+    // True if this indirection is an unaligned memory operation.
+    bool IsUnaligned() const
+    {
+        return (gtFlags & GTF_IND_UNALIGNED) != 0;
+    }
+
 #if DEBUGGABLE_GENTREE
 protected:
     friend GenTree;
@@ -5089,18 +5124,6 @@ struct GenTreeBlk : public GenTreeIndir
         return (m_layout != nullptr) ? m_layout->GetSize() : 0;
     }
 
-    // True if this BlkOpNode is a volatile memory operation.
-    bool IsVolatile() const
-    {
-        return (gtFlags & GTF_BLK_VOLATILE) != 0;
-    }
-
-    // True if this BlkOpNode is an unaligned memory operation.
-    bool IsUnaligned() const
-    {
-        return (gtFlags & GTF_BLK_UNALIGNED) != 0;
-    }
-
     // Instruction selection: during codegen time, what code sequence we will be using
     // to encode this operation.
     enum