Move PHIElimination's SplitCriticalEdge for MachineBasicBlocks out

into a utility routine, teach it how to update MachineLoopInfo, and
make use of it in MachineLICM to split critical edges on demand.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106555 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 1 insertions, 52 deletions

diff --git a/lib/CodeGen/PHIElimination.cpp b/lib/CodeGen/PHIElimination.cpp
index 4271a142309..007d4d9611c 100644
--- a/lib/CodeGen/PHIElimination.cpp
+++ b/lib/CodeGen/PHIElimination.cpp
@@ -34,7 +34,6 @@
 using namespace llvm;
 
 STATISTIC(NumAtomic, "Number of atomic phis lowered");
-STATISTIC(NumSplits, "Number of critical edges split on demand");
 STATISTIC(NumReused, "Number of reused lowered phis");
 
 char PHIElimination::ID = 0;
@@ -391,58 +390,8 @@ bool llvm::PHIElimination::SplitPHIEdges(MachineFunction &MF,
       // (not considering PHI nodes). If the register is live in to this block
       // anyway, we would gain nothing from splitting.
       if (!LV.isLiveIn(Reg, MBB) && LV.isLiveOut(Reg, *PreMBB))
-        SplitCriticalEdge(PreMBB, &MBB);
+        PreMBB->SplitCriticalEdge(&MBB, this);
     }
   }
   return true;
 }
-
-MachineBasicBlock *PHIElimination::SplitCriticalEdge(MachineBasicBlock *A,
-                                                     MachineBasicBlock *B) {
-  assert(A && B && "Missing MBB end point");
-
-  MachineFunction *MF = A->getParent();
-  DebugLoc dl;  // FIXME: this is nowhere
-
-  // We may need to update A's terminator, but we can't do that if AnalyzeBranch
-  // fails. If A uses a jump table, we won't touch it.
-  const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
-  MachineBasicBlock *TBB = 0, *FBB = 0;
-  SmallVector<MachineOperand, 4> Cond;
-  if (TII->AnalyzeBranch(*A, TBB, FBB, Cond))
-    return NULL;
-
-  ++NumSplits;
-
-  MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
-  MF->insert(llvm::next(MachineFunction::iterator(A)), NMBB);
-  DEBUG(dbgs() << "PHIElimination splitting critical edge:"
-        " BB#" << A->getNumber()
-        << " -- BB#" << NMBB->getNumber()
-        << " -- BB#" << B->getNumber() << '\n');
-
-  A->ReplaceUsesOfBlockWith(B, NMBB);
-  A->updateTerminator();
-
-  // Insert unconditional "jump B" instruction in NMBB if necessary.
-  NMBB->addSuccessor(B);
-  if (!NMBB->isLayoutSuccessor(B)) {
-    Cond.clear();
-    MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, B, NULL, Cond, dl);
-  }
-
-  // Fix PHI nodes in B so they refer to NMBB instead of A
-  for (MachineBasicBlock::iterator i = B->begin(), e = B->end();
-       i != e && i->isPHI(); ++i)
-    for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2)
-      if (i->getOperand(ni+1).getMBB() == A)
-        i->getOperand(ni+1).setMBB(NMBB);
-
-  if (LiveVariables *LV=getAnalysisIfAvailable<LiveVariables>())
-    LV->addNewBlock(NMBB, A, B);
-
-  if (MachineDominatorTree *MDT=getAnalysisIfAvailable<MachineDominatorTree>())
-    MDT->addNewBlock(NMBB, A);
-
-  return NMBB;
-}