1 files changed, 126 insertions, 0 deletions
diff --git a/contrib/llvm/lib/CodeGen/MachineBranchProbabilityInfo.cpp b/contrib/llvm/lib/CodeGen/MachineBranchProbabilityInfo.cpp
new file mode 100644
index 000000000000..447921147f03
--- /dev/null
+++ b/contrib/llvm/lib/CodeGen/MachineBranchProbabilityInfo.cpp
@@ -0,0 +1,126 @@
+//===- MachineBranchProbabilityInfo.cpp - Machine Branch Probability Info -===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This analysis uses probability info stored in Machine Basic Blocks.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Instructions.h"
+#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+
+INITIALIZE_PASS_BEGIN(MachineBranchProbabilityInfo, "machine-branch-prob",
+                      "Machine Branch Probability Analysis", false, true)
+INITIALIZE_PASS_END(MachineBranchProbabilityInfo, "machine-branch-prob",
+                    "Machine Branch Probability Analysis", false, true)
+
+char MachineBranchProbabilityInfo::ID = 0;
+
+void MachineBranchProbabilityInfo::anchor() { }
+
+uint32_t MachineBranchProbabilityInfo::
+getSumForBlock(const MachineBasicBlock *MBB, uint32_t &Scale) const {
+  // First we compute the sum with 64-bits of precision, ensuring that cannot
+  // overflow by bounding the number of weights considered. Hopefully no one
+  // actually needs 2^32 successors.
+  assert(MBB->succ_size() < UINT32_MAX);
+  uint64_t Sum = 0;
+  Scale = 1;
+  for (MachineBasicBlock::const_succ_iterator I = MBB->succ_begin(),
+       E = MBB->succ_end(); I != E; ++I) {
+    uint32_t Weight = getEdgeWeight(MBB, I);
+    Sum += Weight;
+  }
+
+  // If the computed sum fits in 32-bits, we're done.
+  if (Sum <= UINT32_MAX)
+    return Sum;
+
+  // Otherwise, compute the scale necessary to cause the weights to fit, and
+  // re-sum with that scale applied.
+  assert((Sum / UINT32_MAX) < UINT32_MAX);
+  Scale = (Sum / UINT32_MAX) + 1;
+  Sum = 0;
+  for (MachineBasicBlock::const_succ_iterator I = MBB->succ_begin(),
+       E = MBB->succ_end(); I != E; ++I) {
+    uint32_t Weight = getEdgeWeight(MBB, I);
+    Sum += Weight / Scale;
+  }
+  assert(Sum <= UINT32_MAX);
+  return Sum;
+}
+
+uint32_t MachineBranchProbabilityInfo::
+getEdgeWeight(const MachineBasicBlock *Src,
+              MachineBasicBlock::const_succ_iterator Dst) const {
+  uint32_t Weight = Src->getSuccWeight(Dst);
+  if (!Weight)
+    return DEFAULT_WEIGHT;
+  return Weight;
+}
+
+uint32_t MachineBranchProbabilityInfo::
+getEdgeWeight(const MachineBasicBlock *Src,
+              const MachineBasicBlock *Dst) const {
+  // This is a linear search. Try to use the const_succ_iterator version when
+  // possible.
+  return getEdgeWeight(Src, std::find(Src->succ_begin(), Src->succ_end(), Dst));
+}
+
+bool MachineBranchProbabilityInfo::isEdgeHot(MachineBasicBlock *Src,
+                                             MachineBasicBlock *Dst) const {
+  // Hot probability is at least 4/5 = 80%
+  // FIXME: Compare against a static "hot" BranchProbability.
+  return getEdgeProbability(Src, Dst) > BranchProbability(4, 5);
+}
+
+MachineBasicBlock *
+MachineBranchProbabilityInfo::getHotSucc(MachineBasicBlock *MBB) const {
+  uint32_t MaxWeight = 0;
+  MachineBasicBlock *MaxSucc = 0;
+  for (MachineBasicBlock::const_succ_iterator I = MBB->succ_begin(),
+       E = MBB->succ_end(); I != E; ++I) {
+    uint32_t Weight = getEdgeWeight(MBB, I);
+    if (Weight > MaxWeight) {
+      MaxWeight = Weight;
+      MaxSucc = *I;
+    }
+  }
+
+  if (getEdgeProbability(MBB, MaxSucc) >= BranchProbability(4, 5))
+    return MaxSucc;
+
+  return 0;
+}
+
+BranchProbability
+MachineBranchProbabilityInfo::getEdgeProbability(MachineBasicBlock *Src,
+                                                 MachineBasicBlock *Dst) const {
+  uint32_t Scale = 1;
+  uint32_t D = getSumForBlock(Src, Scale);
+  uint32_t N = getEdgeWeight(Src, Dst) / Scale;
+
+  return BranchProbability(N, D);
+}
+
+raw_ostream &MachineBranchProbabilityInfo::
+printEdgeProbability(raw_ostream &OS, MachineBasicBlock *Src,
+                     MachineBasicBlock *Dst) const {
+
+  const BranchProbability Prob = getEdgeProbability(Src, Dst);
+  OS << "edge MBB#" << Src->getNumber() << " -> MBB#" << Dst->getNumber()
+     << " probability is "  << Prob 
+     << (isEdgeHot(Src, Dst) ? " [HOT edge]\n" : "\n");
+
+  return OS;
+}