[llvm] 806a2b1 - [MC] Reorder MCFragment members to decrease padding

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2020-01-05T19:09:40-08:00
New Revision: 806a2b1f3d8850eb88f1f9338e86b6398841c961

URL: https://github.com/llvm/llvm-project/commit/806a2b1f3d8850eb88f1f9338e86b6398841c961
DIFF: https://github.com/llvm/llvm-project/commit/806a2b1f3d8850eb88f1f9338e86b6398841c961.diff

LOG: [MC] Reorder MCFragment members to decrease padding

sizeof(MCFragment) does not change, but some if its subclasses do, e.g.
on a 64-bit platform,
sizeof(MCEncodedFragment) decreases from 64 to 56,
sizeof(MCDataFragment) decreases from 224 to 216.

Added: 
    

Modified: 
    llvm/include/llvm/MC/MCFragment.h
    llvm/lib/MC/MCFragment.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/MC/MCFragment.h b/llvm/include/llvm/MC/MCFragment.h
index 1ecbdbfa9806..4722e9b2fa2b 100644
--- a/llvm/include/llvm/MC/MCFragment.h
+++ b/llvm/include/llvm/MC/MCFragment.h
@@ -50,33 +50,24 @@ class MCFragment : public ilist_node_with_parent<MCFragment, MCSection> {
   };
 
 private:
-  FragmentType Kind;
-
-protected:
-  bool HasInstructions;
-
-private:
-  /// The layout order of this fragment.
-  unsigned LayoutOrder;
-
   /// The data for the section this fragment is in.
   MCSection *Parent;
 
   /// The atom this fragment is in, as represented by its defining symbol.
   const MCSymbol *Atom;
 
-  /// \name Assembler Backend Data
-  /// @{
-  //
-  // FIXME: This could all be kept private to the assembler implementation.
-
   /// The offset of this fragment in its section. This is ~0 until
   /// initialized.
   uint64_t Offset;
 
-  /// @}
+  /// The layout order of this fragment.
+  unsigned LayoutOrder;
+
+  FragmentType Kind;
 
 protected:
+  bool HasInstructions;
+
   MCFragment(FragmentType Kind, bool HasInstructions,
              MCSection *Parent = nullptr);
 

diff  --git a/llvm/lib/MC/MCFragment.cpp b/llvm/lib/MC/MCFragment.cpp
index f6b64c8fa95d..a96b8e86aed3 100644
--- a/llvm/lib/MC/MCFragment.cpp
+++ b/llvm/lib/MC/MCFragment.cpp
@@ -234,8 +234,8 @@ void ilist_alloc_traits<MCFragment>::deleteNode(MCFragment *V) { V->destroy(); }
 
 MCFragment::MCFragment(FragmentType Kind, bool HasInstructions,
                        MCSection *Parent)
-    : Kind(Kind), HasInstructions(HasInstructions), LayoutOrder(0),
-      Parent(Parent), Atom(nullptr), Offset(~UINT64_C(0)) {
+    : Parent(Parent), Atom(nullptr), Offset(~UINT64_C(0)), LayoutOrder(0),
+      Kind(Kind), HasInstructions(HasInstructions) {
   if (Parent && !isa<MCDummyFragment>(*this))
     Parent->getFragmentList().push_back(this);
 }