From 670f8e5ba8c30c971de6daa21b50e93d99869d38 Mon Sep 17 00:00:00 2001
From: Xinliang David Li <davidxl@google.com>
Date: Fri, 3 Jun 2016 23:48:36 +0000
Subject: [PATCH] Replace hard coded probability threshold with parameter /NFC

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@271751 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/MachineBlockPlacement.cpp        |  4 +++-
 lib/CodeGen/MachineBranchProbabilityInfo.cpp | 17 ++++++++++-------
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/lib/CodeGen/MachineBlockPlacement.cpp b/lib/CodeGen/MachineBlockPlacement.cpp
index 9df4da2f41f..c562af9d964 100644
--- a/lib/CodeGen/MachineBlockPlacement.cpp
+++ b/lib/CodeGen/MachineBlockPlacement.cpp
@@ -116,6 +116,8 @@ static cl::opt<unsigned> JumpInstCost("jump-inst-cost",
                                       cl::desc("Cost of jump instructions."),
                                       cl::init(1), cl::Hidden);
 
+extern cl::opt<unsigned> StaticLikelyProb;
+
 namespace {
 class BlockChain;
 /// \brief Type for our function-wide basic block -> block chain mapping.
@@ -405,7 +407,7 @@ MachineBasicBlock *
 MachineBlockPlacement::selectBestSuccessor(MachineBasicBlock *BB,
                                            BlockChain &Chain,
                                            const BlockFilterSet *BlockFilter) {
-  const BranchProbability HotProb(4, 5); // 80%
+  const BranchProbability HotProb(StaticLikelyProb, 100);
 
   MachineBasicBlock *BestSucc = nullptr;
   auto BestProb = BranchProbability::getZero();
diff --git a/lib/CodeGen/MachineBranchProbabilityInfo.cpp b/lib/CodeGen/MachineBranchProbabilityInfo.cpp
index cf6d4018cb7..3554e4efa5f 100644
--- a/lib/CodeGen/MachineBranchProbabilityInfo.cpp
+++ b/lib/CodeGen/MachineBranchProbabilityInfo.cpp
@@ -24,9 +24,14 @@ INITIALIZE_PASS_BEGIN(MachineBranchProbabilityInfo, "machine-branch-prob",
 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 to be considered very likely"),
+    cl::init(80), cl::Hidden);
+
 char MachineBranchProbabilityInfo::ID = 0;
 
-void MachineBranchProbabilityInfo::anchor() { }
+void MachineBranchProbabilityInfo::anchor() {}
 
 BranchProbability MachineBranchProbabilityInfo::getEdgeProbability(
     const MachineBasicBlock *Src,
@@ -42,11 +47,9 @@ BranchProbability MachineBranchProbabilityInfo::getEdgeProbability(
                             std::find(Src->succ_begin(), Src->succ_end(), Dst));
 }
 
-bool
-MachineBranchProbabilityInfo::isEdgeHot(const MachineBasicBlock *Src,
-                                        const MachineBasicBlock *Dst) const {
-  // Hot probability is at least 4/5 = 80%
-  static BranchProbability HotProb(4, 5);
+bool MachineBranchProbabilityInfo::isEdgeHot(
+    const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const {
+  BranchProbability HotProb(StaticLikelyProb, 100);
   return getEdgeProbability(Src, Dst) > HotProb;
 }
 
@@ -63,7 +66,7 @@ MachineBranchProbabilityInfo::getHotSucc(MachineBasicBlock *MBB) const {
     }
   }
 
-  static BranchProbability HotProb(4, 5);
+  BranchProbability HotProb(StaticLikelyProb, 100);
   if (getEdgeProbability(MBB, MaxSucc) >= HotProb)
     return MaxSucc;