[llvm-commits] [llvm] r122811 - /llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp

[Cameron Zwarich]

Author: zwarich
Date: Tue Jan  4 10:24:51 2011
New Revision: 122811

URL: http://llvm.org/viewvc/llvm-project?rev=122811&view=rev
Log:
Switch to path halving from path compression for a small speedup. This also
makes getLeader() nonrecursive.

Modified:
    llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp

Modified: llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp?rev=122811&r1=122810&r2=122811&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp (original)
+++ llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp Tue Jan  4 10:24:51 2011
@@ -400,12 +400,18 @@
 
 StrongPHIElimination::Node*
 StrongPHIElimination::Node::getLeader() {
-  Node* parentPointer = parent.getPointer();
-  if (parentPointer == this)
-    return this;
-  Node* newParent = parentPointer->getLeader();
-  parent.setPointer(newParent);
-  return newParent;
+  Node* N = this;
+  Node* Parent = parent.getPointer();
+  Node* Grandparent = Parent->parent.getPointer();
+
+  while (Parent != Grandparent) {
+    N->parent.setPointer(Grandparent);
+    N = Grandparent;
+    Parent = Parent->parent.getPointer();
+    Grandparent = Parent->parent.getPointer();
+  }
+
+  return Parent;
 }
 
 unsigned StrongPHIElimination::getRegColor(unsigned Reg) {