Vendor import of llvm release_32 branch r168974 (effectively, 3.2 RC2):

http://llvm.org/svn/llvm-project/llvm/branches/release_32@168974

1 files changed, 28 insertions, 10 deletions

diff --git a/include/llvm/Analysis/BranchProbabilityInfo.h b/include/llvm/Analysis/BranchProbabilityInfo.h
index 006daa0..c0567da 100644
--- a/include/llvm/Analysis/BranchProbabilityInfo.h
+++ b/include/llvm/Analysis/BranchProbabilityInfo.h
@@ -28,11 +28,14 @@ class raw_ostream;
 ///
 /// This is a function analysis pass which provides information on the relative
 /// probabilities of each "edge" in the function's CFG where such an edge is
-/// defined by a pair of basic blocks. The probability for a given block and
-/// a successor block are always relative to the probabilities of the other
-/// successor blocks. Another way of looking at it is that the probabilities
-/// for a given block B and each of its successors should sum to exactly
-/// one (100%).
+/// defined by a pair (PredBlock and an index in the successors). The
+/// probability of an edge from one block is always relative to the
+/// probabilities of other edges from the block. The probabilites of all edges
+/// from a block sum to exactly one (100%).
+/// We use a pair (PredBlock and an index in the successors) to uniquely
+/// identify an edge, since we can have multiple edges from Src to Dst.
+/// As an example, we can have a switch which jumps to Dst with value 0 and
+/// value 10.
 class BranchProbabilityInfo : public FunctionPass {
 public:
   static char ID;
@@ -52,6 +55,12 @@ public:
   /// leaving the 'Src' block. The returned probability is never zero, and can
   /// only be one if the source block has only one successor.
   BranchProbability getEdgeProbability(const BasicBlock *Src,
+                                       unsigned IndexInSuccessors) const;
+
+  /// \brief Get the probability of going from Src to Dst.
+  ///
+  /// It returns the sum of all probabilities for edges from Src to Dst.
+  BranchProbability getEdgeProbability(const BasicBlock *Src,
                                        const BasicBlock *Dst) const;
 
   /// \brief Test if an edge is hot relative to other out-edges of the Src.
@@ -74,25 +83,34 @@ public:
   raw_ostream &printEdgeProbability(raw_ostream &OS, const BasicBlock *Src,
                                     const BasicBlock *Dst) const;
 
-  /// \brief Get the raw edge weight calculated for the block pair.
+  /// \brief Get the raw edge weight calculated for the edge.
   ///
   /// This returns the raw edge weight. It is guaranteed to fall between 1 and
   /// UINT32_MAX. Note that the raw edge weight is not meaningful in isolation.
   /// This interface should be very carefully, and primarily by routines that
   /// are updating the analysis by later calling setEdgeWeight.
+  uint32_t getEdgeWeight(const BasicBlock *Src,
+                         unsigned IndexInSuccessors) const;
+
+  /// \brief Get the raw edge weight calculated for the block pair.
+  ///
+  /// This returns the sum of all raw edge weights from Src to Dst.
+  /// It is guaranteed to fall between 1 and UINT32_MAX.
   uint32_t getEdgeWeight(const BasicBlock *Src, const BasicBlock *Dst) const;
 
-  /// \brief Set the raw edge weight for the block pair.
+  /// \brief Set the raw edge weight for a given edge.
   ///
-  /// This allows a pass to explicitly set the edge weight for a block. It can
+  /// This allows a pass to explicitly set the edge weight for an edge. It can
   /// be used when updating the CFG to update and preserve the branch
   /// probability information. Read the implementation of how these edge
   /// weights are calculated carefully before using!
-  void setEdgeWeight(const BasicBlock *Src, const BasicBlock *Dst,
+  void setEdgeWeight(const BasicBlock *Src, unsigned IndexInSuccessors,
                      uint32_t Weight);
 
 private:
-  typedef std::pair<const BasicBlock *, const BasicBlock *> Edge;
+  // Since we allow duplicate edges from one basic block to another, we use
+  // a pair (PredBlock and an index in the successors) to specify an edge.
+  typedef std::pair<const BasicBlock *, unsigned> Edge;
 
   // Default weight value. Used when we don't have information about the edge.
   // TODO: DEFAULT_WEIGHT makes sense during static predication, when none of