[PATCH] D148237: [BPI] Add method to swap outgoing edges probabilities

[Aleksandr Popov via Phabricator via llvm-commits]

aleksandr.popov updated this revision to Diff 514576.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D148237/new/

https://reviews.llvm.org/D148237

Files:
  llvm/include/llvm/Analysis/BranchProbabilityInfo.h
  llvm/include/llvm/IR/Instructions.h
  llvm/lib/Analysis/BranchProbabilityInfo.cpp
  llvm/lib/IR/Instructions.cpp
  llvm/unittests/Analysis/BranchProbabilityInfoTest.cpp


Index: llvm/unittests/Analysis/BranchProbabilityInfoTest.cpp
===================================================================
--- llvm/unittests/Analysis/BranchProbabilityInfoTest.cpp
+++ llvm/unittests/Analysis/BranchProbabilityInfoTest.cpp
@@ -115,10 +115,10 @@
   auto ProbEdge1 = BPI->getEdgeProbability(LoopHeaderBB, 1U);
   EXPECT_LT(ProbEdge0, ProbEdge1);
 
-  Branch->swapSuccessors();
+  Branch->swapSuccessors(BPI);
   // TODO: Check the probabilities are swapped as well as the edges
-  EXPECT_EQ(ProbEdge0, BPI->getEdgeProbability(LoopHeaderBB, 0U));
-  EXPECT_EQ(ProbEdge1, BPI->getEdgeProbability(LoopHeaderBB, 1U));
+  EXPECT_EQ(ProbEdge0, BPI->getEdgeProbability(LoopHeaderBB, 1U));
+  EXPECT_EQ(ProbEdge1, BPI->getEdgeProbability(LoopHeaderBB, 0U));
 }
 
 } // end anonymous namespace
Index: llvm/lib/IR/Instructions.cpp
===================================================================
--- llvm/lib/IR/Instructions.cpp
+++ llvm/lib/IR/Instructions.cpp
@@ -13,6 +13,7 @@
 
 #include "llvm/IR/Instructions.h"
 #include "LLVMContextImpl.h"
+#include "llvm/Analysis/BranchProbabilityInfo.h"
 #include "llvm/ADT/SmallBitVector.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Twine.h"
@@ -1440,7 +1441,7 @@
   SubclassOptionalData = BI.SubclassOptionalData;
 }
 
-void BranchInst::swapSuccessors() {
+void BranchInst::swapSuccessors(BranchProbabilityInfo *BPI) {
   assert(isConditional() &&
          "Cannot swap successors of an unconditional branch");
   Op<-1>().swap(Op<-2>());
@@ -1448,6 +1449,8 @@
   // Update profile metadata if present and it matches our structural
   // expectations.
   swapProfMetadata();
+  if (BPI && getParent())
+    BPI->swapSuccEdgesProbabilities(getParent());
 }
 
 //===----------------------------------------------------------------------===//
Index: llvm/lib/Analysis/BranchProbabilityInfo.cpp
===================================================================
--- llvm/lib/Analysis/BranchProbabilityInfo.cpp
+++ llvm/lib/Analysis/BranchProbabilityInfo.cpp
@@ -1175,6 +1175,14 @@
   }
 }
 
+void BranchProbabilityInfo::swapSuccEdgesProbabilities(const BasicBlock *Src) {
+  assert(Src->getTerminator()->getNumSuccessors() == 2);
+  if (!Probs.contains(std::make_pair(Src, 0)))
+    return; // No probability is set for edges from Src
+  assert(Probs.contains(std::make_pair(Src, 1)));
+  std::swap(Probs[std::make_pair(Src, 0)], Probs[std::make_pair(Src, 1)]);
+}
+
 raw_ostream &
 BranchProbabilityInfo::printEdgeProbability(raw_ostream &OS,
                                             const BasicBlock *Src,
Index: llvm/include/llvm/IR/Instructions.h
===================================================================
--- llvm/include/llvm/IR/Instructions.h
+++ llvm/include/llvm/IR/Instructions.h
@@ -3275,7 +3275,7 @@
   /// Swaps the successors of the branch instruction. This also swaps any
   /// branch weight metadata associated with the instruction so that it
   /// continues to map correctly to each operand.
-  void swapSuccessors();
+  void swapSuccessors(BranchProbabilityInfo *BPI = nullptr);
 
   iterator_range<succ_op_iterator> successors() {
     return make_range(
Index: llvm/include/llvm/Analysis/BranchProbabilityInfo.h
===================================================================
--- llvm/include/llvm/Analysis/BranchProbabilityInfo.h
+++ llvm/include/llvm/Analysis/BranchProbabilityInfo.h
@@ -189,6 +189,9 @@
   /// unset for source.
   void copyEdgeProbabilities(BasicBlock *Src, BasicBlock *Dst);
 
+  /// Swap outgoing edges probabilities for \p Src with branch terminator
+  void swapSuccEdgesProbabilities(const BasicBlock *Src);
+
   static BranchProbability getBranchProbStackProtector(bool IsLikely) {
     static const BranchProbability LikelyProb((1u << 20) - 1, 1u << 20);
     return IsLikely ? LikelyProb : LikelyProb.getCompl();


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