Branch profiling: floating-point avoidance.

Patch by: Jakub Staszak!

Introduces BranchProbability. Changes unsigned to uint32_t all over and
uint64_t only when overflow is expected.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132867 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 68 insertions, 8 deletions

diff --git a/include/llvm/Analysis/BranchProbabilityInfo.h b/include/llvm/Analysis/BranchProbabilityInfo.h
index bf2a6a765f..91f289da7c 100644
--- a/include/llvm/Analysis/BranchProbabilityInfo.h
+++ b/include/llvm/Analysis/BranchProbabilityInfo.h
@@ -15,19 +15,24 @@
 #define LLVM_ANALYSIS_BRANCHPROBABILITYINFO_H
 
 #include "llvm/InitializePasses.h"
+#include "llvm/Support/BranchProbability.h"
 #include "llvm/Analysis/LoopInfo.h"
-#include "llvm/Support/Debug.h"
 
 namespace llvm {
 
+class raw_ostream;
+
 class BranchProbabilityInfo : public FunctionPass {
 
   // Default weight value. Used when we don't have information about the edge.
-  static const unsigned int DEFAULT_WEIGHT = 16;
+  static const uint32_t DEFAULT_WEIGHT = 16;
 
   typedef std::pair<BasicBlock *, BasicBlock *> Edge;
 
-  DenseMap<Edge, unsigned> Weights;
+  DenseMap<Edge, uint32_t> Weights;
+
+  // Get sum of the block successors' weights.
+  uint32_t getSumForBlock(BasicBlock *BB) const;
 
 public:
   static char ID;
@@ -43,12 +48,12 @@ public:
 
   bool runOnFunction(Function &F);
 
-  // Returned value is between 1 and UINT_MAX. Look at BranchProbabilityInfo.cpp
-  // for details.
-  unsigned getEdgeWeight(BasicBlock *Src, BasicBlock *Dst) const;
+  // Returned value is between 1 and UINT32_MAX. Look at
+  // BranchProbabilityInfo.cpp for details.
+  uint32_t getEdgeWeight(BasicBlock *Src, BasicBlock *Dst) const;
 
   // Look at BranchProbabilityInfo.cpp for details. Use it with caution!
-  void setEdgeWeight(BasicBlock *Src, BasicBlock *Dst, unsigned Weight);
+  void setEdgeWeight(BasicBlock *Src, BasicBlock *Dst, uint32_t Weight);
 
   // A 'Hot' edge is an edge which probability is >= 80%.
   bool isEdgeHot(BasicBlock *Src, BasicBlock *Dst) const;
@@ -56,11 +61,16 @@ public:
   // Return a hot successor for the block BB or null if there isn't one.
   BasicBlock *getHotSucc(BasicBlock *BB) const;
 
+  // Return a probability as a fraction between 0 (0% probability) and
+  // 1 (100% probability), however the value is never equal to 0, and can be 1
+  // only iff SRC block has only one successor.
+  BranchProbability getEdgeProbability(BasicBlock *Src, BasicBlock *Dst) const;
+
   // Print value between 0 (0% probability) and 1 (100% probability),
   // however the value is never equal to 0, and can be 1 only iff SRC block
   // has only one successor.
   raw_ostream &printEdgeProbability(raw_ostream &OS, BasicBlock *Src,
-                                   BasicBlock *Dst) const;
+                                    BasicBlock *Dst) const;
 };
 
 }
diff --git a/include/llvm/Support/BranchProbability.h b/include/llvm/Support/BranchProbability.h
new file mode 100644
index 0000000000..7ba649133b
--- /dev/null
+++ b/include/llvm/Support/BranchProbability.h
@@ -0,0 +1,50 @@
+//===- BranchProbability.h - Branch Probability Analysis --------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Definition of BranchProbability shared by IR and Machine Instructions.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_BRANCHPROBABILITY_H
+#define LLVM_SUPPORT_BRANCHPROBABILITY_H
+
+#include "llvm/Support/DataTypes.h"
+
+namespace llvm {
+
+class raw_ostream;
+class BranchProbabilityInfo;
+class MachineBranchProbabilityInfo;
+class MachineBasicBlock;
+
+// This class represents Branch Probability as a non-negative fraction.
+class BranchProbability {
+  friend class BranchProbabilityInfo;
+  friend class MachineBranchProbabilityInfo;
+  friend class MachineBasicBlock;
+
+  // Numerator
+  uint32_t N;
+
+  // Denominator
+  uint32_t D;
+
+  BranchProbability(uint32_t n, uint32_t d);
+
+public:
+  raw_ostream &print(raw_ostream &OS) const;
+
+  void dump() const;
+};
+
+raw_ostream &operator<<(raw_ostream &OS, const BranchProbability &Prob);
+
+}
+
+#endif