Add new interfaces to MBB for manipulating successors with probabilities instead of weights. NFC.

This is part-1 of the patch that replaces all edge weights in MBB by
probabilities, which only adds new interfaces. No functional changes.

Differential revision: http://reviews.llvm.org/D13908

llvm-svn: 252083

1 files changed, 82 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index ab865ff..1fdaf32 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -523,6 +523,25 @@ void MachineBasicBlock::addSuccessorWithoutWeight(MachineBasicBlock *Succ) {
   Succ->addPredecessor(this);
 }
 
+void MachineBasicBlock::addSuccessor(MachineBasicBlock *Succ,
+                                     BranchProbability Prob) {
+  // Probability list is either empty (if successor list isn't empty, this means
+  // disabled optimization) or has the same size as successor list.
+  if (!(Probs.empty() && !Successors.empty()))
+    Probs.push_back(Prob);
+  Successors.push_back(Succ);
+  Succ->addPredecessor(this);
+}
+
+void MachineBasicBlock::addSuccessorWithoutProb(MachineBasicBlock *Succ) {
+  // We need to make sure probability list is either empty or has the same size
+  // of successor list. When this function is called, we can safely delete all
+  // probability in the list.
+  Probs.clear();
+  Successors.push_back(Succ);
+  Succ->addPredecessor(this);
+}
+
 void MachineBasicBlock::removeSuccessor(MachineBasicBlock *Succ) {
   Succ->removePredecessor(this);
   succ_iterator I = std::find(Successors.begin(), Successors.end(), Succ);
@@ -534,6 +553,13 @@ void MachineBasicBlock::removeSuccessor(MachineBasicBlock *Succ) {
     Weights.erase(WI);
   }
 
+  // If probability list is empty it means we don't use it (disabled
+  // optimization).
+  if (!Probs.empty()) {
+    probability_iterator WI = getProbabilityIterator(I);
+    Probs.erase(WI);
+  }
+
   Successors.erase(I);
 }
 
@@ -547,6 +573,13 @@ MachineBasicBlock::removeSuccessor(succ_iterator I) {
     Weights.erase(WI);
   }
 
+  // If probability list is empty it means we don't use it (disabled
+  // optimization).
+  if (!Probs.empty()) {
+    probability_iterator WI = getProbabilityIterator(I);
+    Probs.erase(WI);
+  }
+
   (*I)->removePredecessor(this);
   return Successors.erase(I);
 }
@@ -588,6 +621,12 @@ void MachineBasicBlock::replaceSuccessor(MachineBasicBlock *Old,
     *getWeightIterator(NewI) += *OldWI;
     Weights.erase(OldWI);
   }
+  // Update its probability instead of adding a duplicate edge.
+  if (!Probs.empty()) {
+    probability_iterator OldPI = getProbabilityIterator(OldI);
+    *getProbabilityIterator(NewI) += *OldPI;
+    Probs.erase(OldPI);
+  }
   Successors.erase(OldI);
 }
 
@@ -1120,6 +1159,21 @@ uint32_t MachineBasicBlock::getSuccWeight(const_succ_iterator Succ) const {
   return *getWeightIterator(Succ);
 }
 
+/// Return probability of the edge from this block to MBB. If probability list
+/// is empty, return a default probability which is 1/N, where N is the number
+/// of successors. If the probability of the given successor is unknown, then
+/// sum up all known probabilities and return the complement of the sum divided
+/// by the number of unknown probabilities.
+BranchProbability
+MachineBasicBlock::getSuccProbability(const_succ_iterator Succ) const {
+  if (Probs.empty())
+    return BranchProbability(1, succ_size());
+
+  auto Prob = *getProbabilityIterator(Succ);
+  assert(!Prob.isUnknown());
+  return Prob;
+}
+
 /// Set successor weight of a given iterator.
 void MachineBasicBlock::setSuccWeight(succ_iterator I, uint32_t Weight) {
   if (Weights.empty())
@@ -1127,6 +1181,15 @@ void MachineBasicBlock::setSuccWeight(succ_iterator I, uint32_t Weight) {
   *getWeightIterator(I) = Weight;
 }
 
+/// Set successor probability of a given iterator.
+void MachineBasicBlock::setSuccProbability(succ_iterator I,
+                                           BranchProbability Prob) {
+  assert(!Prob.isUnknown());
+  if (Probs.empty())
+    return;
+  *getProbabilityIterator(I) = Prob;
+}
+
 /// Return wight iterator corresonding to the I successor iterator.
 MachineBasicBlock::weight_iterator MachineBasicBlock::
 getWeightIterator(MachineBasicBlock::succ_iterator I) {
@@ -1145,6 +1208,25 @@ getWeightIterator(MachineBasicBlock::const_succ_iterator I) const {
   return Weights.begin() + index;
 }
 
+/// Return probability iterator corresonding to the I successor iterator.
+MachineBasicBlock::probability_iterator
+MachineBasicBlock::getProbabilityIterator(MachineBasicBlock::succ_iterator I) {
+  assert(Probs.size() == Successors.size() && "Async probability list!");
+  const size_t index = std::distance(Successors.begin(), I);
+  assert(index < Probs.size() && "Not a current successor!");
+  return Probs.begin() + index;
+}
+
+/// Return probability iterator corresonding to the I successor iterator
+MachineBasicBlock::const_probability_iterator
+MachineBasicBlock::getProbabilityIterator(
+    MachineBasicBlock::const_succ_iterator I) const {
+  assert(Probs.size() == Successors.size() && "Async probability list!");
+  const size_t index = std::distance(Successors.begin(), I);
+  assert(index < Probs.size() && "Not a current successor!");
+  return Probs.begin() + index;
+}
+
 /// Return whether (physical) register "Reg" has been <def>ined and not <kill>ed
 /// as of just before "MI".
 ///