[BPI][NFC] Reuse post dominantor tree from analysis manager when available

Summary: Currenlty BPI unconditionally creates post dominator tree each time. While this is not incorrect we can save compile time by reusing existing post dominator tree (when it's valid) provided by analysis manager.

Reviewers: skatkov, taewookoh, yrouban

Reviewed By: skatkov

Subscribers: hiraditya, steven_wu, dexonsmith, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D78987

1 files changed, 19 insertions, 7 deletions

diff --git a/llvm/lib/Analysis/BranchProbabilityInfo.cpp b/llvm/lib/Analysis/BranchProbabilityInfo.cpp
index ae99d63..99f253c 100644
--- a/llvm/lib/Analysis/BranchProbabilityInfo.cpp
+++ b/llvm/lib/Analysis/BranchProbabilityInfo.cpp
@@ -61,6 +61,7 @@ INITIALIZE_PASS_BEGIN(BranchProbabilityInfoWrapperPass, "branch-prob",
                       "Branch Probability Analysis", false, true)
 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
 INITIALIZE_PASS_END(BranchProbabilityInfoWrapperPass, "branch-prob",
                     "Branch Probability Analysis", false, true)
 
@@ -980,7 +981,8 @@ void BranchProbabilityInfo::eraseBlock(const BasicBlock *BB) {
 }
 
 void BranchProbabilityInfo::calculate(const Function &F, const LoopInfo &LI,
-                                      const TargetLibraryInfo *TLI) {
+                                      const TargetLibraryInfo *TLI,
+                                      PostDominatorTree *PDT) {
   LLVM_DEBUG(dbgs() << "---- Branch Probability Info : " << F.getName()
                     << " ----\n\n");
   LastF = &F; // Store the last function we ran on for printing.
@@ -1008,10 +1010,15 @@ void BranchProbabilityInfo::calculate(const Function &F, const LoopInfo &LI,
     LLVM_DEBUG(dbgs() << "\n");
   }
 
-  std::unique_ptr<PostDominatorTree> PDT =
-      std::make_unique<PostDominatorTree>(const_cast<Function &>(F));
-  computePostDominatedByUnreachable(F, PDT.get());
-  computePostDominatedByColdCall(F, PDT.get());
+  std::unique_ptr<PostDominatorTree> PDTPtr;
+
+  if (!PDT) {
+    PDTPtr = std::make_unique<PostDominatorTree>(const_cast<Function &>(F));
+    PDT = PDTPtr.get();
+  }
+
+  computePostDominatedByUnreachable(F, PDT);
+  computePostDominatedByColdCall(F, PDT);
 
   // Walk the basic blocks in post-order so that we can build up state about
   // the successors of a block iteratively.
@@ -1057,6 +1064,7 @@ void BranchProbabilityInfoWrapperPass::getAnalysisUsage(
   AU.addRequired<DominatorTreeWrapperPass>();
   AU.addRequired<LoopInfoWrapperPass>();
   AU.addRequired<TargetLibraryInfoWrapperPass>();
+  AU.addRequired<PostDominatorTreeWrapperPass>();
   AU.setPreservesAll();
 }
 
@@ -1064,7 +1072,9 @@ bool BranchProbabilityInfoWrapperPass::runOnFunction(Function &F) {
   const LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
   const TargetLibraryInfo &TLI =
       getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
-  BPI.calculate(F, LI, &TLI);
+  PostDominatorTree &PDT =
+      getAnalysis<PostDominatorTreeWrapperPass>().getPostDomTree();
+  BPI.calculate(F, LI, &TLI, &PDT);
   return false;
 }
 
@@ -1079,7 +1089,9 @@ AnalysisKey BranchProbabilityAnalysis::Key;
 BranchProbabilityInfo
 BranchProbabilityAnalysis::run(Function &F, FunctionAnalysisManager &AM) {
   BranchProbabilityInfo BPI;
-  BPI.calculate(F, AM.getResult<LoopAnalysis>(F), &AM.getResult<TargetLibraryAnalysis>(F));
+  BPI.calculate(F, AM.getResult<LoopAnalysis>(F),
+                &AM.getResult<TargetLibraryAnalysis>(F),
+                &AM.getResult<PostDominatorTreeAnalysis>(F));
   return BPI;
 }