Set the branch probability of branching to the 'normal' destination of an invoke

instruction to something absurdly high, while setting the probability of
branching to the 'unwind' destination to the bare minimum. This should set cause
the normal destination's invoke blocks to be moved closer to the invoke.

PR13612

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161944 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Analysis/BranchProbabilityInfo.h b/include/llvm/Analysis/BranchProbabilityInfo.h
index 2ced7967ed5b345362097e5c9469a83f3f82fb11..006daa082946c2a5e19ff30cee6ab31a739763ae 100644 (file)
--- a/include/llvm/Analysis/BranchProbabilityInfo.h
+++ b/include/llvm/Analysis/BranchProbabilityInfo.h
@@ -122,6 +122,7 @@ private:
   bool calcLoopBranchHeuristics(BasicBlock *BB);
   bool calcZeroHeuristics(BasicBlock *BB);
   bool calcFloatingPointHeuristics(BasicBlock *BB);
+  bool calcInvokeHeuristics(BasicBlock *BB);
 };
 
 }

diff --git a/lib/Analysis/BranchProbabilityInfo.cpp b/lib/Analysis/BranchProbabilityInfo.cpp
index 2730ce6c63bfe4b3cb9f650e9de8df50c74498f1..b255ce6dba5162aaa8e02ce6fef7f800c2759fc6 100644 (file)
--- a/lib/Analysis/BranchProbabilityInfo.cpp
+++ b/lib/Analysis/BranchProbabilityInfo.cpp
@@ -1,4 +1,4 @@
-//===-- BranchProbabilityInfo.cpp - Branch Probability Analysis -*- C++ -*-===//
+//===-- BranchProbabilityInfo.cpp - Branch Probability Analysis -----------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -78,6 +78,19 @@ static const uint32_t ZH_NONTAKEN_WEIGHT = 12;
 static const uint32_t FPH_TAKEN_WEIGHT = 20;
 static const uint32_t FPH_NONTAKEN_WEIGHT = 12;
 
+/// \brief Invoke-terminating normal branch taken weight
+///
+/// This is the weight for branching to the normal destination of an invoke
+/// instruction. We expect this to happen most of the time. Set the weight to an
+/// absurdly high value so that nested loops subsume it.
+static const uint32_t IH_TAKEN_WEIGHT = 1024 * 1024 - 1;
+
+/// \brief Invoke-terminating normal branch not-taken weight.
+///
+/// This is the weight for branching to the unwind destination of an invoke
+/// instruction. This is essentially never taken.
+static const uint32_t IH_NONTAKEN_WEIGHT = 1;
+
 // Standard weight value. Used when none of the heuristics set weight for
 // the edge.
 static const uint32_t NORMAL_WEIGHT = 16;
@@ -371,6 +384,19 @@ bool BranchProbabilityInfo::calcFloatingPointHeuristics(BasicBlock *BB) {
   return true;
 }
 
+bool BranchProbabilityInfo::calcInvokeHeuristics(BasicBlock *BB) {
+  InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator());
+  if (!II)
+    return false;
+
+  BasicBlock *Normal = II->getNormalDest();
+  BasicBlock *Unwind = II->getUnwindDest();
+
+  setEdgeWeight(BB, Normal, IH_TAKEN_WEIGHT);
+  setEdgeWeight(BB, Unwind, IH_NONTAKEN_WEIGHT);
+  return true;
+}
+
 void BranchProbabilityInfo::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addRequired<LoopInfo>();
   AU.setPreservesAll();
@@ -397,7 +423,9 @@ bool BranchProbabilityInfo::runOnFunction(Function &F) {
       continue;
     if (calcZeroHeuristics(*I))
       continue;
-    calcFloatingPointHeuristics(*I);
+    if (calcFloatingPointHeuristics(*I))
+      continue;
+    calcInvokeHeuristics(*I);
   }
 
   PostDominatedByUnreachable.clear();