1 files changed, 23 insertions, 6 deletions

diff --git a/llvm/lib/CodeGen/MachineSink.cpp b/llvm/lib/CodeGen/MachineSink.cpp
index 261af54..3ac64d7 100644
--- a/llvm/lib/CodeGen/MachineSink.cpp
+++ b/llvm/lib/CodeGen/MachineSink.cpp
@@ -21,6 +21,7 @@
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
 #include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
 #include "llvm/CodeGen/MachinePostDominators.h"
@@ -41,6 +42,12 @@ SplitEdges("machine-sink-split",
            cl::desc("Split critical edges during machine sinking"),
            cl::init(true), cl::Hidden);
 
+static cl::opt<bool>
+UseBlockFreqInfo("machine-sink-bfi",
+           cl::desc("Use block frequency info to find successors to sink"),
+           cl::init(true), cl::Hidden);
+
+
 STATISTIC(NumSunk,      "Number of machine instructions sunk");
 STATISTIC(NumSplit,     "Number of critical edges split");
 STATISTIC(NumCoalesces, "Number of copies coalesced");
@@ -53,6 +60,7 @@ namespace {
     MachineDominatorTree *DT;      // Machine dominator tree
     MachinePostDominatorTree *PDT; // Machine post dominator tree
     MachineLoopInfo *LI;
+    const MachineBlockFrequencyInfo *MBFI;
     AliasAnalysis *AA;
 
     // Remember which edges have been considered for breaking.
@@ -81,6 +89,8 @@ namespace {
       AU.addPreserved<MachineDominatorTree>();
       AU.addPreserved<MachinePostDominatorTree>();
       AU.addPreserved<MachineLoopInfo>();
+      if (UseBlockFreqInfo)
+        AU.addRequired<MachineBlockFrequencyInfo>();
     }
 
     void releaseMemory() override {
@@ -247,6 +257,7 @@ bool MachineSinking::runOnMachineFunction(MachineFunction &MF) {
   DT = &getAnalysis<MachineDominatorTree>();
   PDT = &getAnalysis<MachinePostDominatorTree>();
   LI = &getAnalysis<MachineLoopInfo>();
+  MBFI = UseBlockFreqInfo ? &getAnalysis<MachineBlockFrequencyInfo>() : nullptr;
   AA = &getAnalysis<AliasAnalysis>();
 
   bool EverMadeChange = false;
@@ -566,14 +577,20 @@ MachineBasicBlock *MachineSinking::FindSuccToSinkTo(MachineInstr *MI,
       }
 
       // Otherwise, we should look at all the successors and decide which one
-      // we should sink to.
-      // We give successors with smaller loop depth higher priority.
-      SmallVector<MachineBasicBlock*, 4> Succs(MBB->succ_begin(), MBB->succ_end());
-      // Sort Successors according to their loop depth.
+      // we should sink to. If we have reliable block frequency information
+      // (frequency != 0) available, give successors with smaller frequencies
+      // higher priority, otherwise prioritize smaller loop depths.
+      SmallVector<MachineBasicBlock*, 4> Succs(MBB->succ_begin(),
+                                               MBB->succ_end());
+      // Sort Successors according to their loop depth or block frequency info.
       std::stable_sort(
           Succs.begin(), Succs.end(),
-          [this](const MachineBasicBlock *LHS, const MachineBasicBlock *RHS) {
-            return LI->getLoopDepth(LHS) < LI->getLoopDepth(RHS);
+          [this](const MachineBasicBlock *L, const MachineBasicBlock *R) {
+            uint64_t LHSFreq = MBFI ? MBFI->getBlockFreq(L).getFrequency() : 0;
+            uint64_t RHSFreq = MBFI ? MBFI->getBlockFreq(R).getFrequency() : 0;
+            bool HasBlockFreq = LHSFreq != 0 && RHSFreq != 0;
+            return HasBlockFreq ? LHSFreq < RHSFreq
+                                : LI->getLoopDepth(L) < LI->getLoopDepth(R);
           });
       for (SmallVectorImpl<MachineBasicBlock *>::iterator SI = Succs.begin(),
              E = Succs.end(); SI != E; ++SI) {