1 files changed, 9 insertions, 25 deletions

diff --git a/lib/CodeGen/PHIElimination.cpp b/lib/CodeGen/PHIElimination.cpp
index b3802ed6725d0..2e30cc6abd328 100644
--- a/lib/CodeGen/PHIElimination.cpp
+++ b/lib/CodeGen/PHIElimination.cpp
@@ -353,7 +353,7 @@ bool llvm::PHIElimination::SplitPHIEdges(MachineFunction &MF,
       // We break edges when registers are live out from the predecessor block
       // (not considering PHI nodes). If the register is live in to this block
       // anyway, we would gain nothing from splitting.
-      if (isLiveOut(Reg, *PreMBB, LV) && !isLiveIn(Reg, MBB, LV))
+      if (!LV.isLiveIn(Reg, MBB) && isLiveOut(Reg, *PreMBB, LV))
         SplitCriticalEdge(PreMBB, &MBB);
     }
   }
@@ -406,22 +406,6 @@ bool llvm::PHIElimination::isLiveOut(unsigned Reg, const MachineBasicBlock &MBB,
   return false;
 }
 
-bool llvm::PHIElimination::isLiveIn(unsigned Reg, const MachineBasicBlock &MBB,
-                                    LiveVariables &LV) {
-  LiveVariables::VarInfo &VI = LV.getVarInfo(Reg);
-
-  if (VI.AliveBlocks.test(MBB.getNumber()))
-    return true;
-
-  // defined in MBB?
-  const MachineInstr *Def = MRI->getVRegDef(Reg);
-  if (Def && Def->getParent() == &MBB)
-    return false;
-
-  // killed in MBB?
-  return VI.findKill(&MBB);
-}
-
 MachineBasicBlock *PHIElimination::SplitCriticalEdge(MachineBasicBlock *A,
                                                      MachineBasicBlock *B) {
   assert(A && B && "Missing MBB end point");
@@ -439,21 +423,21 @@ MachineBasicBlock *PHIElimination::SplitCriticalEdge(MachineBasicBlock *A,
   ++NumSplits;
 
   MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
-  MF->push_back(NMBB);
+  MF->insert(next(MachineFunction::iterator(A)), NMBB);
   DEBUG(errs() << "PHIElimination splitting critical edge:"
         " BB#" << A->getNumber()
         << " -- BB#" << NMBB->getNumber()
         << " -- BB#" << B->getNumber() << '\n');
 
   A->ReplaceUsesOfBlockWith(B, NMBB);
-  // If A may fall through to B, we may have to insert a branch.
-  if (A->isLayoutSuccessor(B))
-    A->updateTerminator();
+  A->updateTerminator();
 
-  // Insert unconditional "jump B" instruction in NMBB.
+  // Insert unconditional "jump B" instruction in NMBB if necessary.
   NMBB->addSuccessor(B);
-  Cond.clear();
-  MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, B, NULL, Cond);
+  if (!NMBB->isLayoutSuccessor(B)) {
+    Cond.clear();
+    MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, B, NULL, Cond);
+  }
 
   // Fix PHI nodes in B so they refer to NMBB instead of A
   for (MachineBasicBlock::iterator i = B->begin(), e = B->end();
@@ -463,7 +447,7 @@ MachineBasicBlock *PHIElimination::SplitCriticalEdge(MachineBasicBlock *A,
         i->getOperand(ni+1).setMBB(NMBB);
 
   if (LiveVariables *LV=getAnalysisIfAvailable<LiveVariables>())
-    LV->addNewBlock(NMBB, A);
+    LV->addNewBlock(NMBB, A, B);
 
   if (MachineDominatorTree *MDT=getAnalysisIfAvailable<MachineDominatorTree>())
     MDT->addNewBlock(NMBB, A);