1 files changed, 91 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/MachineBranchProbabilityInfo.cpp b/llvm/lib/CodeGen/MachineBranchProbabilityInfo.cpp
new file mode 100644
index 000000000000..d2277ce51746
--- /dev/null
+++ b/llvm/lib/CodeGen/MachineBranchProbabilityInfo.cpp
@@ -0,0 +1,91 @@
+//===- MachineBranchProbabilityInfo.cpp - Machine Branch Probability Info -===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This analysis uses probability info stored in Machine Basic Blocks.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/IR/Instructions.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)
+
+cl::opt<unsigned>
+    StaticLikelyProb("static-likely-prob",
+                     cl::desc("branch probability threshold in percentage"
+                              "to be considered very likely"),
+                     cl::init(80), cl::Hidden);
+
+cl::opt<unsigned> ProfileLikelyProb(
+    "profile-likely-prob",
+    cl::desc("branch probability threshold in percentage to be considered"
+             " very likely when profile is available"),
+    cl::init(51), cl::Hidden);
+
+char MachineBranchProbabilityInfo::ID = 0;
+
+void MachineBranchProbabilityInfo::anchor() {}
+
+BranchProbability MachineBranchProbabilityInfo::getEdgeProbability(
+    const MachineBasicBlock *Src,
+    MachineBasicBlock::const_succ_iterator Dst) const {
+  return Src->getSuccProbability(Dst);
+}
+
+BranchProbability MachineBranchProbabilityInfo::getEdgeProbability(
+    const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const {
+  // This is a linear search. Try to use the const_succ_iterator version when
+  // possible.
+  return getEdgeProbability(Src, find(Src->successors(), Dst));
+}
+
+bool MachineBranchProbabilityInfo::isEdgeHot(
+    const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const {
+  BranchProbability HotProb(StaticLikelyProb, 100);
+  return getEdgeProbability(Src, Dst) > HotProb;
+}
+
+MachineBasicBlock *
+MachineBranchProbabilityInfo::getHotSucc(MachineBasicBlock *MBB) const {
+  auto MaxProb = BranchProbability::getZero();
+  MachineBasicBlock *MaxSucc = nullptr;
+  for (MachineBasicBlock::const_succ_iterator I = MBB->succ_begin(),
+       E = MBB->succ_end(); I != E; ++I) {
+    auto Prob = getEdgeProbability(MBB, I);
+    if (Prob > MaxProb) {
+      MaxProb = Prob;
+      MaxSucc = *I;
+    }
+  }
+
+  BranchProbability HotProb(StaticLikelyProb, 100);
+  if (getEdgeProbability(MBB, MaxSucc) >= HotProb)
+    return MaxSucc;
+
+  return nullptr;
+}
+
+raw_ostream &MachineBranchProbabilityInfo::printEdgeProbability(
+    raw_ostream &OS, const MachineBasicBlock *Src,
+    const MachineBasicBlock *Dst) const {
+
+  const BranchProbability Prob = getEdgeProbability(Src, Dst);
+  OS << "edge " << printMBBReference(*Src) << " -> " << printMBBReference(*Dst)
+     << " probability is " << Prob
+     << (isEdgeHot(Src, Dst) ? " [HOT edge]\n" : "\n");
+
+  return OS;
+}