From 5c0068f8075e4e687df8c7f2fee1c47224077af9 Mon Sep 17 00:00:00 2001
From: Bill Wendling <isanbard@gmail.com>
Date: Sun, 8 Apr 2012 10:20:49 +0000
Subject: Remove the 'Parent' pointer from the MDNodeOperand class.

An MDNode has a list of MDNodeOperands allocated directly after it as part of
its allocation. Therefore, the Parent of the MDNodeOperands can be found by
walking back through the operands to the beginning of that list. Mark the first
operand's value pointer as being the 'first' operand so that we know where the
beginning of said list is.

This saves a *lot* of space during LTO with -O0 -g flags.

llvm-svn: 154280
---
 llvm/lib/VMCore/Metadata.cpp | 37 ++++++++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 11 deletions(-)

(limited to 'llvm')

diff --git a/llvm/lib/VMCore/Metadata.cpp b/llvm/lib/VMCore/Metadata.cpp
index d5f6aa92bdb..e6fd64c0afa 100644
--- a/llvm/lib/VMCore/Metadata.cpp
+++ b/llvm/lib/VMCore/Metadata.cpp
@@ -50,14 +50,26 @@ MDString *MDString::get(LLVMContext &Context, StringRef Str) {
 // Use CallbackVH to hold MDNode operands.
 namespace llvm {
 class MDNodeOperand : public CallbackVH {
-  MDNode *Parent;
+  MDNode *getParent() {
+    MDNodeOperand *Cur = this;
+
+    while (Cur->getValPtrInt() != 1)
+      --Cur;
+
+    assert(Cur->getValPtrInt() == 1 &&
+           "Couldn't find the beginning of the operand list!");
+    return reinterpret_cast<MDNode*>(Cur) - 1;
+  }
+
 public:
-  MDNodeOperand(Value *V, MDNode *P) : CallbackVH(V), Parent(P) {}
+  MDNodeOperand(Value *V) : CallbackVH(V) {}
   ~MDNodeOperand() {}
 
-  void set(Value *V) {
-    setValPtr(V);
-  }
+  void set(Value *V) { this->setValPtr(V); }
+
+  /// setAsFirstOperand - Accessor method to mark the operand as the first in
+  /// the list.
+  void setAsFirstOperand(unsigned V) { this->setValPtrInt(V); }
 
   virtual void deleted();
   virtual void allUsesReplacedWith(Value *NV);
@@ -66,15 +78,13 @@ public:
 
 
 void MDNodeOperand::deleted() {
-  Parent->replaceOperand(this, 0);
+  getParent()->replaceOperand(this, 0);
 }
 
 void MDNodeOperand::allUsesReplacedWith(Value *NV) {
-  Parent->replaceOperand(this, NV);
+  getParent()->replaceOperand(this, NV);
 }
 
-
-
 //===----------------------------------------------------------------------===//
 // MDNode implementation.
 //
@@ -102,8 +112,13 @@ MDNode::MDNode(LLVMContext &C, ArrayRef<Value*> Vals, bool isFunctionLocal)
   // Initialize the operand list, which is co-allocated on the end of the node.
   unsigned i = 0;
   for (MDNodeOperand *Op = getOperandPtr(this, 0), *E = Op+NumOperands;
-       Op != E; ++Op, ++i)
-    new (Op) MDNodeOperand(Vals[i], this);
+       Op != E; ++Op, ++i) {
+    new (Op) MDNodeOperand(Vals[i]);
+
+    // Mark the first MDNodeOperand as being the first in the list of operands.
+    if (i == 0)
+      Op->setAsFirstOperand(1);
+  }
 }
 
 
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