From 75dd7f0c4a2b3fb9e9d4d5a0517591810c57ed92 Mon Sep 17 00:00:00 2001
From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Tue, 21 Aug 2012 21:03:40 +0000
Subject: MaximumSpanningTree::EdgeWeightCompare: Make this comparator actually
 be a strict weak ordering, and don't pass possibly-null pointers to dyn_cast.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162314 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../Instrumentation/MaximumSpanningTree.h          | 53 ++++++++++++----------
 1 file changed, 28 insertions(+), 25 deletions(-)

diff --git a/lib/Transforms/Instrumentation/MaximumSpanningTree.h b/lib/Transforms/Instrumentation/MaximumSpanningTree.h
index f76c77e1bd..a4bb5a66af 100644
--- a/lib/Transforms/Instrumentation/MaximumSpanningTree.h
+++ b/lib/Transforms/Instrumentation/MaximumSpanningTree.h
@@ -26,30 +26,6 @@ namespace llvm {
   /// The type parameter T determines the type of the nodes of the graph.
   template <typename T>
   class MaximumSpanningTree {
-
-    // A comparing class for comparing weighted edges.
-    template <typename CT>
-    struct EdgeWeightCompare {
-      bool operator()(typename MaximumSpanningTree<CT>::EdgeWeight X, 
-                      typename MaximumSpanningTree<CT>::EdgeWeight Y) const {
-        if (X.second > Y.second) return true;
-        if (X.second < Y.second) return false;
-        if (const BasicBlock *BBX = dyn_cast<BasicBlock>(X.first.first)) {
-          if (const BasicBlock *BBY = dyn_cast<BasicBlock>(Y.first.first)) {
-            if (BBX->size() > BBY->size()) return true;
-            if (BBX->size() < BBY->size()) return false;
-          }
-        }
-        if (const BasicBlock *BBX = dyn_cast<BasicBlock>(X.first.second)) {
-          if (const BasicBlock *BBY = dyn_cast<BasicBlock>(Y.first.second)) {
-            if (BBX->size() > BBY->size()) return true;
-            if (BBX->size() < BBY->size()) return false;
-          }
-        }
-        return false;
-      }
-    };
-
   public:
     typedef std::pair<const T*, const T*> Edge;
     typedef std::pair<Edge, double> EdgeWeight;
@@ -59,6 +35,33 @@ namespace llvm {
 
     MaxSpanTree MST;
 
+  private:
+    // A comparing class for comparing weighted edges.
+    struct EdgeWeightCompare {
+      static bool getBlockSize(const T *X) {
+        const BasicBlock *BB = dyn_cast_or_null<BasicBlock>(X);
+        return BB ? BB->size() : 0;
+      }
+
+      bool operator()(EdgeWeight X, EdgeWeight Y) const {
+        if (X.second > Y.second) return true;
+        if (X.second < Y.second) return false;
+
+        // Equal edge weights: break ties by comparing block sizes.
+        size_t XSizeA = getBlockSize(X.first.first);
+        size_t YSizeA = getBlockSize(Y.first.first);
+        if (XSizeA > YSizeA) return true;
+        if (XSizeA < YSizeA) return false;
+
+        size_t XSizeB = getBlockSize(X.first.second);
+        size_t YSizeB = getBlockSize(Y.first.second);
+        if (XSizeB > YSizeB) return true;
+        if (XSizeB < YSizeB) return false;
+
+        return false;
+      }
+    };
+
   public:
     static char ID; // Class identification, replacement for typeinfo
 
@@ -66,7 +69,7 @@ namespace llvm {
     /// spanning tree.
     MaximumSpanningTree(EdgeWeights &EdgeVector) {
 
-      std::stable_sort(EdgeVector.begin(), EdgeVector.end(), EdgeWeightCompare<T>());
+      std::stable_sort(EdgeVector.begin(), EdgeVector.end(), EdgeWeightCompare());
 
       // Create spanning tree, Forest contains a special data structure
       // that makes checking if two nodes are already in a common (sub-)tree
-- 
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