[MachineBasicBlock] Make the pass argument truly mandatory when

splitting edges.

MachineBasicBlock::SplitCriticalEdges will crash if a nullptr would have
been passed for the Pass argument. Do not allow that by turning this
argument into a reference.
The alternative would have been to make the Pass a truly optional
argument, but although this is easy to do, I was afraid users using it
like this would not be aware the livness information, dominator tree and
such would silently be broken.

llvm-svn: 267052

llvm/include/llvm/CodeGen/MachineBasicBlock.h

@@ -506,7 +506,7 @@ public:
   ///
   /// This function updates LiveVariables, MachineDominatorTree, and
   /// MachineLoopInfo, as applicable.
-  MachineBasicBlock *SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P);
+  MachineBasicBlock *SplitCriticalEdge(MachineBasicBlock *Succ, Pass &P);
 
   /// Check if the edge between this block and the given successor \p
   /// Succ, can be split. If this returns true a subsequent call to

llvm/lib/CodeGen/MachineBasicBlock.cpp

@@ -711,8 +711,8 @@ bool MachineBasicBlock::canFallThrough() {
   return FBB == nullptr;
 }
 
-MachineBasicBlock *
-MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) {
+MachineBasicBlock *MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ,
+                                                        Pass &P) {
   if (!canSplitCriticalEdge(Succ))
     return nullptr;
 
@@ -726,8 +726,8 @@ MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) {
         << " -- BB#" << NMBB->getNumber()
         << " -- BB#" << Succ->getNumber() << '\n');
 
-  LiveIntervals *LIS = P->getAnalysisIfAvailable<LiveIntervals>();
-  SlotIndexes *Indexes = P->getAnalysisIfAvailable<SlotIndexes>();
+  LiveIntervals *LIS = P.getAnalysisIfAvailable<LiveIntervals>();
+  SlotIndexes *Indexes = P.getAnalysisIfAvailable<SlotIndexes>();
   if (LIS)
     LIS->insertMBBInMaps(NMBB);
   else if (Indexes)
@@ -736,7 +736,7 @@ MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) {
   // On some targets like Mips, branches may kill virtual registers. Make sure
   // that LiveVariables is properly updated after updateTerminator replaces the
   // terminators.
-  LiveVariables *LV = P->getAnalysisIfAvailable<LiveVariables>();
+  LiveVariables *LV = P.getAnalysisIfAvailable<LiveVariables>();
 
   // Collect a list of virtual registers killed by the terminators.
   SmallVector<unsigned, 4> KilledRegs;
@@ -916,10 +916,10 @@ MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) {
   }
 
   if (MachineDominatorTree *MDT =
-      P->getAnalysisIfAvailable<MachineDominatorTree>())
+          P.getAnalysisIfAvailable<MachineDominatorTree>())
     MDT->recordSplitCriticalEdge(this, Succ, NMBB);
 
-  if (MachineLoopInfo *MLI = P->getAnalysisIfAvailable<MachineLoopInfo>())
+  if (MachineLoopInfo *MLI = P.getAnalysisIfAvailable<MachineLoopInfo>())
     if (MachineLoop *TIL = MLI->getLoopFor(this)) {
       // If one or the other blocks were not in a loop, the new block is not
       // either, and thus LI doesn't need to be updated.

llvm/lib/CodeGen/MachineLICM.cpp

@@ -1382,7 +1382,7 @@ MachineBasicBlock *MachineLICM::getCurPreheader() {
         return nullptr;
       }
 
-      CurPreheader = Pred->SplitCriticalEdge(CurLoop->getHeader(), this);
+      CurPreheader = Pred->SplitCriticalEdge(CurLoop->getHeader(), *this);
       if (!CurPreheader) {
         CurPreheader = reinterpret_cast<MachineBasicBlock *>(-1);
         return nullptr;

llvm/lib/CodeGen/MachineSink.cpp

@@ -284,7 +284,7 @@ bool MachineSinking::runOnMachineFunction(MachineFunction &MF) {
 
     // If we have anything we marked as toSplit, split it now.
     for (auto &Pair : ToSplit) {
-      auto NewSucc = Pair.first->SplitCriticalEdge(Pair.second, this);
+      auto NewSucc = Pair.first->SplitCriticalEdge(Pair.second, *this);
       if (NewSucc != nullptr) {
         DEBUG(dbgs() << " *** Splitting critical edge:"
               " BB#" << Pair.first->getNumber()

llvm/lib/CodeGen/PHIElimination.cpp

@@ -610,7 +610,7 @@ bool PHIElimination::SplitPHIEdges(MachineFunction &MF,
       }
       if (!ShouldSplit && !SplitAllCriticalEdges)
         continue;
-      if (!PreMBB->SplitCriticalEdge(&MBB, this)) {
+      if (!PreMBB->SplitCriticalEdge(&MBB, *this)) {
         DEBUG(dbgs() << "Failed to split critical edge.\n");
         continue;
       }