1 files changed, 14 insertions, 21 deletions

diff --git a/llvm/lib/CodeGen/MachineSink.cpp b/llvm/lib/CodeGen/MachineSink.cpp
index da83cac..b82d4e6 100644
--- a/llvm/lib/CodeGen/MachineSink.cpp
+++ b/llvm/lib/CodeGen/MachineSink.cpp
@@ -24,6 +24,7 @@
 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
 #include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
+#include "llvm/CodeGen/MachinePostDominators.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
@@ -54,8 +55,9 @@ namespace {
   class MachineSinking : public MachineFunctionPass {
     const TargetInstrInfo *TII;
     const TargetRegisterInfo *TRI;
-    MachineRegisterInfo  *MRI;  // Machine register information
-    MachineDominatorTree *DT;   // Machine dominator tree
+    MachineRegisterInfo  *MRI;     // Machine register information
+    MachineDominatorTree *DT;      // Machine dominator tree
+    MachinePostDominatorTree *PDT; // Machine post dominator tree
     MachineLoopInfo *LI;
     const MachineBlockFrequencyInfo *MBFI;
     AliasAnalysis *AA;
@@ -81,8 +83,10 @@ namespace {
       MachineFunctionPass::getAnalysisUsage(AU);
       AU.addRequired<AliasAnalysis>();
       AU.addRequired<MachineDominatorTree>();
+      AU.addRequired<MachinePostDominatorTree>();
       AU.addRequired<MachineLoopInfo>();
       AU.addPreserved<MachineDominatorTree>();
+      AU.addPreserved<MachinePostDominatorTree>();
       AU.addPreserved<MachineLoopInfo>();
       if (UseBlockFreqInfo)
         AU.addRequired<MachineBlockFrequencyInfo>();
@@ -249,6 +253,7 @@ bool MachineSinking::runOnMachineFunction(MachineFunction &MF) {
   TRI = MF.getSubtarget().getRegisterInfo();
   MRI = &MF.getRegInfo();
   DT = &getAnalysis<MachineDominatorTree>();
+  PDT = &getAnalysis<MachinePostDominatorTree>();
   LI = &getAnalysis<MachineLoopInfo>();
   MBFI = UseBlockFreqInfo ? &getAnalysis<MachineBlockFrequencyInfo>() : nullptr;
   AA = &getAnalysis<AliasAnalysis>();
@@ -467,23 +472,6 @@ static void collectDebugValues(MachineInstr *MI,
   }
 }
 
-/// isPostDominatedBy - Return true if A is post dominated by B.
-static bool isPostDominatedBy(MachineBasicBlock *A, MachineBasicBlock *B) {
-
-  // FIXME - Use real post dominator.
-  if (A->succ_size() != 2)
-    return false;
-  MachineBasicBlock::succ_iterator I = A->succ_begin();
-  if (B == *I)
-    ++I;
-  MachineBasicBlock *OtherSuccBlock = *I;
-  if (OtherSuccBlock->succ_size() != 1 ||
-      *(OtherSuccBlock->succ_begin()) != B)
-    return false;
-
-  return true;
-}
-
 /// isProfitableToSinkTo - Return true if it is profitable to sink MI.
 bool MachineSinking::isProfitableToSinkTo(unsigned Reg, MachineInstr *MI,
                                           MachineBasicBlock *MBB,
@@ -495,8 +483,13 @@ bool MachineSinking::isProfitableToSinkTo(unsigned Reg, MachineInstr *MI,
     return false;
 
   // It is profitable if SuccToSinkTo does not post dominate current block.
-  if (!isPostDominatedBy(MBB, SuccToSinkTo))
-      return true;
+  if (!PDT->dominates(SuccToSinkTo, MBB))
+    return true;
+
+  // It is profitable to sink an instruction from a deeper loop to a shallower
+  // loop, even if the latter post-dominates the former (PR21115).
+  if (LI->getLoopDepth(MBB) > LI->getLoopDepth(SuccToSinkTo))
+    return true;
 
   // Check if only use in post dominated block is PHI instruction.
   bool NonPHIUse = false;