Revert r68073. It's causing a failure in the Apple-style builds.

llvm-svn: 68092

include/llvm/CodeGen/MachineBasicBlock.h

@@ -253,15 +253,6 @@ public:
   /// it returns end()
   iterator getFirstTerminator();
 
-  /// isOnlyReachableViaFallthough - Return true if this basic block has
-  /// exactly one predecessor and the control transfer mechanism between
-  /// the predecessor and this block is a fall-through.
-  bool isOnlyReachableByFallthrough() const {
-    return !pred_empty() &&
-           next(pred_begin()) == pred_end() &&
-           (*pred_begin())->getFirstTerminator() == (*pred_begin())->end();
-  }
-
   void pop_front() { Insts.pop_front(); }
   void pop_back() { Insts.pop_back(); }
   void push_back(MachineInstr *MI) { Insts.push_back(MI); }

lib/CodeGen/Spiller.cpp

@@ -578,6 +578,20 @@ bool LocalSpiller::runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
   DOUT << "**** Post Machine Instrs ****\n";
   DEBUG(MF.dump());
 
+  // See if any of the spills we added are actually dead and can be deleted.
+  for (std::vector<MachineInstr*> >::iterator
+         I = AddedSpills.begin(), E = AddedSpills.end(); I != E; ++I) {
+    MachineInstr *MI = *I;
+
+    if (VRM.OnlyUseOfStackSlot(MI)) {
+      MachineBasicBlock *MBB = MI->getParent();
+      DOUT << "Removed dead store:\t" << *MI;
+      VRM.RemoveMachineInstrFromMaps(MI);
+      MBB->erase(MI);
+      ++NumDSE;
+    }
+  }
+
   // Mark unused spill slots.
   MachineFrameInfo *MFI = MF.getFrameInfo();
   int SS = VRM.getLowSpillSlot();
@@ -588,6 +602,7 @@ bool LocalSpiller::runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
         ++NumDSS;
       }
 
+  AddedSpills.clear();
   return true;
 }
 
@@ -798,9 +813,50 @@ bool LocalSpiller::CommuteToFoldReload(MachineBasicBlock &MBB,
   return false;
 }
 
+void LocalSpiller::RemoveDeadStore(MachineInstr *Store,
+                                   MachineBasicBlock &MBB,
+                                   MachineBasicBlock::iterator &MII,
+                                   SmallSet<MachineInstr*, 4> &ReMatDefs,
+                                   BitVector &RegKills,
+                                   std::vector<MachineOperand*> &KillOps,
+                                   VirtRegMap &VRM) {
+  // If there is a dead store to this stack slot, nuke it now.
+  DOUT << "Removed dead store:\t" << *Store;
+  ++NumDSE;
+  SmallVector<unsigned, 2> KillRegs;
+  InvalidateKills(*Store, RegKills, KillOps, &KillRegs);
+
+  MachineBasicBlock::iterator PrevMII = Store;
+  bool CheckDef = PrevMII != MBB.begin();
+  if (CheckDef) --PrevMII;
+
+  VRM.RemoveMachineInstrFromMaps(Store);
+  MBB.erase(Store);
+
+  if (CheckDef) {
+    // Look at defs of killed registers on the store. Mark the defs as dead
+    // since the store has been deleted and they aren't being reused.
+    for (unsigned j = 0, ee = KillRegs.size(); j != ee; ++j) {
+      bool HasOtherDef = false;
+
+      if (InvalidateRegDef(PrevMII, *MII, KillRegs[j], HasOtherDef)) {
+        MachineInstr *DeadDef = PrevMII;
+
+        if (ReMatDefs.count(DeadDef) && !HasOtherDef) {
+          // FIXME: This assumes a remat def does not have side effects.
+          VRM.RemoveMachineInstrFromMaps(DeadDef);
+          MBB.erase(DeadDef);
+          ++NumDRM;
+        }
+      }
+    }
+  }
+}
+
 /// SpillRegToStackSlot - Spill a register to a specified stack slot. Check if
 /// the last store to the same slot is now dead. If so, remove the last store.
-void LocalSpiller::SpillRegToStackSlot(MachineBasicBlock &MBB,
+void
+LocalSpiller::SpillRegToStackSlot(MachineBasicBlock &MBB,
                                   MachineBasicBlock::iterator &MII,
                                   int Idx, unsigned PhysReg, int StackSlot,
                                   const TargetRegisterClass *RC,
@@ -816,36 +872,8 @@ void LocalSpiller::SpillRegToStackSlot(MachineBasicBlock &MBB,
   DOUT << "Store:\t" << *StoreMI;
 
   // If there is a dead store to this stack slot, nuke it now.
-  if (LastStore) {
-    DOUT << "Removed dead store:\t" << *LastStore;
-    ++NumDSE;
-    SmallVector<unsigned, 2> KillRegs;
-    InvalidateKills(*LastStore, RegKills, KillOps, &KillRegs);
-    MachineBasicBlock::iterator PrevMII = LastStore;
-    bool CheckDef = PrevMII != MBB.begin();
-    if (CheckDef)
-      --PrevMII;
-    VRM.RemoveMachineInstrFromMaps(LastStore);
-    MBB.erase(LastStore);
-    if (CheckDef) {
-      // Look at defs of killed registers on the store. Mark the defs
-      // as dead since the store has been deleted and they aren't
-      // being reused.
-      for (unsigned j = 0, ee = KillRegs.size(); j != ee; ++j) {
-        bool HasOtherDef = false;
-        if (InvalidateRegDef(PrevMII, *MII, KillRegs[j], HasOtherDef)) {
-          MachineInstr *DeadDef = PrevMII;
-          if (ReMatDefs.count(DeadDef) && !HasOtherDef) {
-            // FIXME: This assumes a remat def does not have side
-            // effects.
-            VRM.RemoveMachineInstrFromMaps(DeadDef);
-            MBB.erase(DeadDef);
-            ++NumDRM;
-          }
-        }
-      }
-    }
-  }
+  if (LastStore)
+    RemoveDeadStore(LastStore, MBB, MII, ReMatDefs, RegKills, KillOps, VRM);
 
   LastStore = next(MII);
 
@@ -1060,6 +1088,7 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM,
     if (VRM.isSpillPt(&MI)) {
       std::vector<std::pair<unsigned,bool> > &SpillRegs =
         VRM.getSpillPtSpills(&MI);
+
       for (unsigned i = 0, e = SpillRegs.size(); i != e; ++i) {
         unsigned VirtReg = SpillRegs[i].first;
         bool isKill = SpillRegs[i].second;
@@ -1073,7 +1102,9 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM,
         VRM.addSpillSlotUse(StackSlot, StoreMI);
         DOUT << "Store:\t" << *StoreMI;
         VRM.virtFolded(VirtReg, StoreMI, VirtRegMap::isMod);
+        AddedSpills.push_back(StoreMI);
       }
+
       NextMII = next(MII);
     }
 

lib/CodeGen/Spiller.h

@@ -285,6 +285,7 @@ namespace llvm {
     const TargetRegisterInfo *TRI;
     const TargetInstrInfo *TII;
     DenseMap<MachineInstr*, unsigned> DistanceMap;
+    std::vector<MachineInstr*> AddedSpills;
   public:
     bool runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM);
   private:
@@ -305,6 +306,14 @@ namespace llvm {
                              std::vector<MachineOperand*> &KillOps,
                              const TargetRegisterInfo *TRI,
                              VirtRegMap &VRM);
+    void RemoveDeadStore(MachineInstr *Store,
+                         MachineBasicBlock &MBB,
+                         MachineBasicBlock::iterator &MII,
+                         SmallSet<MachineInstr*, 4> &ReMatDefs,
+                         BitVector &RegKills,
+                         std::vector<MachineOperand*> &KillOps,
+                         VirtRegMap &VRM);
+
     void SpillRegToStackSlot(MachineBasicBlock &MBB,
                              MachineBasicBlock::iterator &MII,
                              int Idx, unsigned PhysReg, int StackSlot,

lib/CodeGen/VirtRegMap.cpp

@@ -188,7 +188,7 @@ void VirtRegMap::RemoveMachineInstrFromMaps(MachineInstr *MI) {
     if (MF->getFrameInfo()->isFixedObjectIndex(FI))
       continue;
     // This stack reference was produced by instruction selection and
-    // is not a spill
+    // is not a spill.
     if (FI < LowSpillSlot)
       continue;
     assert((unsigned)FI-LowSpillSlot < SpillSlotToUsesMap.size()
@@ -201,6 +201,27 @@ void VirtRegMap::RemoveMachineInstrFromMaps(MachineInstr *MI) {
   EmergencySpillMap.erase(MI);
 }
 
+bool VirtRegMap::OnlyUseOfStackSlot(const MachineInstr *MI) const {
+  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+    const MachineOperand &MO = MI->getOperand(i);
+    if (!MO.isFI())
+      continue;
+    int FI = MO.getIndex();
+    if (MF->getFrameInfo()->isFixedObjectIndex(FI))
+      continue;
+    // This stack reference was produced by instruction selection and
+    // is not a spill.
+    if (FI < LowSpillSlot)
+      continue;
+    assert((unsigned)FI-LowSpillSlot < SpillSlotToUsesMap.size()
+           && "Invalid spill slot");
+    if (SpillSlotToUsesMap[FI - LowSpillSlot].size() != 1)
+      return false;
+  }
+
+  return true;
+}
+
 void VirtRegMap::print(std::ostream &OS, const Module* M) const {
   const TargetRegisterInfo* TRI = MF->getTarget().getRegisterInfo();
 

lib/CodeGen/VirtRegMap.h

@@ -430,6 +430,8 @@ namespace llvm {
     /// the folded instruction map and spill point map.
     void RemoveMachineInstrFromMaps(MachineInstr *MI);
 
+    bool OnlyUseOfStackSlot(const MachineInstr *MI) const;
+
     void print(std::ostream &OS, const Module* M = 0) const;
     void print(std::ostream *OS) const { if (OS) print(*OS); }
     void dump() const;

lib/Target/X86/AsmPrinter/X86ATTAsmPrinter.cpp

@@ -238,12 +238,7 @@ bool X86ATTAsmPrinter::runOnMachineFunction(MachineFunction &MF) {
   for (MachineFunction::const_iterator I = MF.begin(), E = MF.end();
        I != E; ++I) {
     // Print a label for the basic block.
-    if (!VerboseAsm && (I->pred_empty() || I->isOnlyReachableByFallthrough())) {
-      // This is an entry block or a block that's only reachable via a
-      // fallthrough edge. In non-VerboseAsm mode, don't print the label.
-      assert((I->pred_empty() || (*I->pred_begin())->isLayoutSuccessor(I)) &&
-             "Fall-through predecessor not adjacent to its successor!");
-    } else {
+    if (!I->pred_empty()) {
       printBasicBlockLabel(I, true, true, VerboseAsm);
       O << '\n';
     }