[llvm-commits] [llvm] r161944 - in /llvm/trunk: include/llvm/Analysis/BranchProbabilityInfo.h lib/Analysis/BranchProbabilityInfo.cpp

[Bill Wendling]

Author: void
Date: Wed Aug 15 07:22:35 2012
New Revision: 161944

URL: http://llvm.org/viewvc/llvm-project?rev=161944&view=rev
Log:
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

Modified:
    llvm/trunk/include/llvm/Analysis/BranchProbabilityInfo.h
    llvm/trunk/lib/Analysis/BranchProbabilityInfo.cpp

Modified: llvm/trunk/include/llvm/Analysis/BranchProbabilityInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/BranchProbabilityInfo.h?rev=161944&r1=161943&r2=161944&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Analysis/BranchProbabilityInfo.h (original)
+++ llvm/trunk/include/llvm/Analysis/BranchProbabilityInfo.h Wed Aug 15 07:22:35 2012
@@ -122,6 +122,7 @@
   bool calcLoopBranchHeuristics(BasicBlock *BB);
   bool calcZeroHeuristics(BasicBlock *BB);
   bool calcFloatingPointHeuristics(BasicBlock *BB);
+  bool calcInvokeHeuristics(BasicBlock *BB);
 };
 
 }

Modified: llvm/trunk/lib/Analysis/BranchProbabilityInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/BranchProbabilityInfo.cpp?rev=161944&r1=161943&r2=161944&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/BranchProbabilityInfo.cpp (original)
+++ llvm/trunk/lib/Analysis/BranchProbabilityInfo.cpp Wed Aug 15 07:22:35 2012
@@ -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 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 @@
   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 @@
       continue;
     if (calcZeroHeuristics(*I))
       continue;
-    calcFloatingPointHeuristics(*I);
+    if (calcFloatingPointHeuristics(*I))
+      continue;
+    calcInvokeHeuristics(*I);
   }
 
   PostDominatedByUnreachable.clear();