From 33d5595d667ba4a880bd7fe785724e8197bef70c Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Thu, 2 Aug 2007 05:29:38 +0000
Subject: [PATCH] Do not emit copies for physical register output if it's not
 used.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40722 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/CodeGen/SelectionDAGNodes.h  |  4 ++++
 lib/CodeGen/SelectionDAG/ScheduleDAG.cpp  |  3 ++-
 lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 27 ++++++++++++++++++++++-
 3 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/include/llvm/CodeGen/SelectionDAGNodes.h b/include/llvm/CodeGen/SelectionDAGNodes.h
index ce7dda40280..3502e895019 100644
--- a/include/llvm/CodeGen/SelectionDAGNodes.h
+++ b/include/llvm/CodeGen/SelectionDAGNodes.h
@@ -858,6 +858,10 @@ public:
   /// operation.
   bool hasNUsesOfValue(unsigned NUses, unsigned Value) const;
 
+  /// hasAnyUseOfValue - Return true if there are any use of the indicated
+  /// value. This method ignores uses of other values defined by this operation.
+  bool hasAnyUseOfValue(unsigned Value) const;
+
   /// isOnlyUse - Return true if this node is the only use of N.
   ///
   bool isOnlyUse(SDNode *N) const;
diff --git a/lib/CodeGen/SelectionDAG/ScheduleDAG.cpp b/lib/CodeGen/SelectionDAG/ScheduleDAG.cpp
index 3738702dc8d..192b0767e36 100644
--- a/lib/CodeGen/SelectionDAG/ScheduleDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/ScheduleDAG.cpp
@@ -676,7 +676,8 @@ void ScheduleDAG::EmitNode(SDNode *Node,
     if (HasPhysRegOuts) {
       for (unsigned i = II.numDefs; i < NumResults; ++i) {
         unsigned Reg = II.ImplicitDefs[i - II.numDefs];
-        EmitCopyFromReg(Node, i, Reg, VRBaseMap);
+        if (Node->hasAnyUseOfValue(i))
+          EmitCopyFromReg(Node, i, Reg, VRBaseMap);
       }
     }
   } else {
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 4b7863d896c..7ac8ea81aa6 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -3242,7 +3242,7 @@ bool SDNode::hasNUsesOfValue(unsigned NUses, unsigned Value) const {
   // If there is only one value, this is easy.
   if (getNumValues() == 1)
     return use_size() == NUses;
-  if (Uses.size() < NUses) return false;
+  if (use_size() < NUses) return false;
 
   SDOperand TheValue(const_cast<SDNode *>(this), Value);
 
@@ -3265,6 +3265,31 @@ bool SDNode::hasNUsesOfValue(unsigned NUses, unsigned Value) const {
 }
 
 
+/// hasAnyUseOfValue - Return true if there are any use of the indicated
+/// value. This method ignores uses of other values defined by this operation.
+bool SDNode::hasAnyUseOfValue(unsigned Value) const {
+  assert(Value < getNumValues() && "Bad value!");
+
+  if (use_size() == 0) return false;
+
+  SDOperand TheValue(const_cast<SDNode *>(this), Value);
+
+  SmallPtrSet<SDNode*, 32> UsersHandled;
+
+  for (SDNode::use_iterator UI = Uses.begin(), E = Uses.end(); UI != E; ++UI) {
+    SDNode *User = *UI;
+    if (User->getNumOperands() == 1 ||
+        UsersHandled.insert(User))     // First time we've seen this?
+      for (unsigned i = 0, e = User->getNumOperands(); i != e; ++i)
+        if (User->getOperand(i) == TheValue) {
+          return true;
+        }
+  }
+
+  return false;
+}
+
+
 /// isOnlyUse - Return true if this node is the only use of N.
 ///
 bool SDNode::isOnlyUse(SDNode *N) const {