[PATCH] D148616: [BPI][Test] Check the probabilities after swapping branch successors

[Aleksandr Popov via Phabricator via llvm-commits]

aleksandr.popov created this revision.
aleksandr.popov added reviewers: mkazantsev, dmakogon, fhahn, nikic.
Herald added subscribers: StephenFan, hiraditya.
Herald added a project: All.
aleksandr.popov requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

https://reviews.llvm.org/D148616

Files:
  llvm/include/llvm/IR/Instructions.h
  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
@@ -83,5 +83,43 @@
   EXPECT_TRUE(BPI.isEdgeHot(EntryBB, ExitBB));
 }
 
+TEST_F(BranchProbabilityInfoTest, SwapProbabilities) {
+  StringRef Assembly = R"(
+    define void @f() {
+    entry:
+      br label %loop
+
+    loop:
+      %iv = phi i32 [ 0, %entry ], [ %iv.next, %loop ]
+      %iv.next = add i32 %iv, 1
+      %cond = icmp slt i32 %iv.next, 10
+      br i1 %cond, label %exit, label %loop
+
+    exit:
+      ret void
+    }
+  )";
+  LLVMContext Context;
+  SMDiagnostic Error;
+  auto M = parseAssemblyString(Assembly, Error, Context);
+  ASSERT_TRUE(M) << "Bad assembly?";
+
+  Function *F = M->getFunction("f");
+  auto *LoopHeaderBB = F->front().getSingleSuccessor();
+  ASSERT_TRUE(LoopHeaderBB != nullptr);
+  BranchInst *Branch = dyn_cast<BranchInst>(LoopHeaderBB->getTerminator());
+  ASSERT_TRUE(Branch != nullptr);
+  // Save the probabilities before successors swapping
+  BranchProbabilityInfo *BPI = &buildBPI(*F);
+  auto ProbEdge0 = BPI->getEdgeProbability(LoopHeaderBB, 0U);
+  auto ProbEdge1 = BPI->getEdgeProbability(LoopHeaderBB, 1U);
+  EXPECT_LT(ProbEdge0, ProbEdge1);
+
+  Branch->swapSuccessors();
+  // 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));
+}
+
 } // end anonymous namespace
 } // end namespace llvm
Index: llvm/lib/IR/Instructions.cpp
===================================================================
--- llvm/lib/IR/Instructions.cpp
+++ llvm/lib/IR/Instructions.cpp
@@ -16,6 +16,7 @@
 #include "llvm/ADT/SmallBitVector.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Twine.h"
+#include "llvm/Analysis/BranchProbabilityInfo.h"
 #include "llvm/IR/Attributes.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/Constant.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/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(


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