Fix a bug that David Greene found in the DAGCombiner's logic

[oota-llvm.git] / lib / CodeGen / PreAllocSplitting.cpp

diff --git a/lib/CodeGen/PreAllocSplitting.cpp b/lib/CodeGen/PreAllocSplitting.cpp
index a538db8be086ed0bc9bda8f119e5def9c2b8d5fa..9e955bd69690d7b169bc56dda7af64b26d833977 100644 (file)
--- a/lib/CodeGen/PreAllocSplitting.cpp
+++ b/lib/CodeGen/PreAllocSplitting.cpp
@@ -224,32 +224,59 @@ PreAllocSplitting::findSpillPoint(MachineBasicBlock *MBB, MachineInstr *MI,
   if (RefsInMBB.empty() && !DefMI) {
     MachineBasicBlock::iterator MII = MBB->begin();
     MachineBasicBlock::iterator EndPt = MI;
+    
+    if (MII == EndPt) return Pt;
+    
     do {
       ++MII;
       unsigned Index = LIs->getInstructionIndex(MII);
       unsigned Gap = LIs->findGapBeforeInstr(Index);
-      if (Gap) {
-        Pt = MII;
-        SpillIndex = Gap;
-        break;
       
       // We can't insert the spill between the barrier (a call), and its
-      // corresponding call frame setup.
-      } else if (prior(MII)->getOpcode() == TRI->getCallFrameSetupOpcode() &&
-                 MII == MachineBasicBlock::iterator(MI))
+      // corresponding call frame setup/teardown.
+      if (prior(MII)->getOpcode() == TRI->getCallFrameSetupOpcode()) {
+        bool reachedBarrier = false;
+        do {
+          if (MII == EndPt) {
+            reachedBarrier = true;
+            break;
+          }
+          ++MII;
+        } while (MII->getOpcode() != TRI->getCallFrameDestroyOpcode());
+        
+        if (reachedBarrier) break;
+      } else if (Gap) {
+        Pt = MII;
+        SpillIndex = Gap;
         break;
+      }
     } while (MII != EndPt);
   } else {
     MachineBasicBlock::iterator MII = MI;
     MachineBasicBlock::iterator EndPt = DefMI
       ? MachineBasicBlock::iterator(DefMI) : MBB->begin();
     
-    // We can't insert the spill between the barrier (a call), and its
-    // corresponding call frame setup.
-    if (prior(MII)->getOpcode() == TRI->getCallFrameSetupOpcode()) --MII;
     while (MII != EndPt && !RefsInMBB.count(MII)) {
       unsigned Index = LIs->getInstructionIndex(MII);
-      if (LIs->hasGapBeforeInstr(Index)) {
+      
+      // We can't insert the spill between the barrier (a call), and its
+      // corresponding call frame setup.
+      if (prior(MII)->getOpcode() == TRI->getCallFrameSetupOpcode()) {
+        --MII;
+        continue;
+      } if (MII->getOpcode() == TRI->getCallFrameDestroyOpcode()) {
+        bool reachedBarrier = false;
+        while (MII->getOpcode() != TRI->getCallFrameSetupOpcode()) {
+          --MII;
+          if (MII == EndPt) {
+            reachedBarrier = true;
+            break;
+          }
+        }
+        
+        if (reachedBarrier) break;
+        else continue;
+      } else if (LIs->hasGapBeforeInstr(Index)) {
         Pt = MII;
         SpillIndex = LIs->findGapBeforeInstr(Index, true);
       }
@@ -279,29 +306,39 @@ PreAllocSplitting::findRestorePoint(MachineBasicBlock *MBB, MachineInstr *MI,
   if (RefsInMBB.empty() && LastIdx >= EndIdx) {
     MachineBasicBlock::iterator MII = MBB->getFirstTerminator();
     MachineBasicBlock::iterator EndPt = MI;
+    
+    if (MII == EndPt) return Pt;
+    
     --MII;
     do {
       unsigned Index = LIs->getInstructionIndex(MII);
       unsigned Gap = LIs->findGapBeforeInstr(Index);
-      if (Gap) {
-        Pt = MII;
-        RestoreIndex = Gap;
-        break;
       
       // We can't insert a restore between the barrier (a call) and its 
       // corresponding call frame teardown.
-      } else if (MII->getOpcode() == TRI->getCallFrameDestroyOpcode() &&
-                 prior(MII) == MachineBasicBlock::iterator(MI))
+      if (MII->getOpcode() == TRI->getCallFrameDestroyOpcode()) {
+        bool reachedBarrier = false;
+        while (MII->getOpcode() != TRI->getCallFrameSetupOpcode()) {
+          --MII;
+          if (MII == EndPt) {
+            reachedBarrier = true;
+            break;
+          }
+        }
+        
+        if (reachedBarrier) break;
+        else continue;
+      } else if (Gap) {
+        Pt = MII;
+        RestoreIndex = Gap;
         break;
+      }
+      
       --MII;
     } while (MII != EndPt);
   } else {
     MachineBasicBlock::iterator MII = MI;
     MII = ++MII;
-    // We can't insert a restore between the barrier (a call) and its 
-    // corresponding call frame teardown.
-    if (MII->getOpcode() == TRI->getCallFrameDestroyOpcode())
-      ++MII;
     
     // FIXME: Limit the number of instructions to examine to reduce
     // compile time?
@@ -310,10 +347,29 @@ PreAllocSplitting::findRestorePoint(MachineBasicBlock *MBB, MachineInstr *MI,
       if (Index > LastIdx)
         break;
       unsigned Gap = LIs->findGapBeforeInstr(Index);
-      if (Gap) {
+      
+      // We can't insert a restore between the barrier (a call) and its 
+      // corresponding call frame teardown.
+      if (MII->getOpcode() == TRI->getCallFrameDestroyOpcode()) {
+        ++MII;
+        continue;
+      } else if (prior(MII)->getOpcode() == TRI->getCallFrameSetupOpcode()) {
+        bool reachedBarrier = false;
+        do {
+          if (MII == MBB->getFirstTerminator() || RefsInMBB.count(MII)) {
+            reachedBarrier = true;
+            break;
+          }
+          
+          ++MII;
+        } while (MII->getOpcode() != TRI->getCallFrameDestroyOpcode());
+        
+        if (reachedBarrier) break;
+      } else if (Gap) {
         Pt = MII;
         RestoreIndex = Gap;
       }
+      
       if (RefsInMBB.count(MII))
         break;
       ++MII;
@@ -654,8 +710,24 @@ PreAllocSplitting::PerformPHIConstructionFallBack(MachineBasicBlock::iterator Us
   }
     
   if (MBB->pred_size() == 1 && !RetVNI->hasPHIKill) {
-    LI->MergeValueNumberInto(RetVNI, IncomingVNs.begin()->second);
-    Phis[MBB] = RetVNI = IncomingVNs.begin()->second;
+    VNInfo* OldVN = RetVNI;
+    VNInfo* NewVN = IncomingVNs.begin()->second;
+    VNInfo* MergedVN = LI->MergeValueNumberInto(OldVN, NewVN);
+    if (MergedVN == OldVN) std::swap(OldVN, NewVN);
+    
+    for (DenseMap<MachineBasicBlock*, VNInfo*>::iterator LOI = LiveOut.begin(),
+         LOE = LiveOut.end(); LOI != LOE; ++LOI)
+      if (LOI->second == OldVN)
+        LOI->second = MergedVN;
+    for (DenseMap<MachineInstr*, VNInfo*>::iterator NVI = NewVNs.begin(),
+         NVE = NewVNs.end(); NVI != NVE; ++NVI)
+      if (NVI->second == OldVN)
+        NVI->second = MergedVN;
+    for (DenseMap<MachineBasicBlock*, VNInfo*>::iterator PI = Phis.begin(),
+         PE = Phis.end(); PI != PE; ++PI)
+      if (PI->second == OldVN)
+        PI->second = MergedVN;
+    RetVNI = MergedVN;
   } else {
     // Otherwise, merge the incoming VNInfos with a phi join.  Create a new
     // VNInfo to represent the joined value.
@@ -1062,7 +1134,10 @@ PreAllocSplitting::SplitRegLiveIntervals(const TargetRegisterClass **RCs,
   // by the current barrier.
   SmallVector<LiveInterval*, 8> Intervals;
   for (const TargetRegisterClass **RC = RCs; *RC; ++RC) {
-    if (TII->IgnoreRegisterClassBarriers(*RC))
+    // FIXME: If it's not safe to move any instruction that defines the barrier
+    // register class, then it means there are some special dependencies which
+    // codegen is not modelling. Ignore these barriers for now.
+    if (!TII->isSafeToMoveRegClassDefs(*RC))
       continue;
     std::vector<unsigned> &VRs = MRI->getRegClassVirtRegs(*RC);
     for (unsigned i = 0, e = VRs.size(); i != e; ++i) {