move isOnlyReachableByFallthrough out of MachineBasicBlock into AsmPrinter,

and add a sparc implementation that knows about delay slots.  Patch by
Nathan Keynes!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96492 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/AsmPrinter.h

@@ -356,6 +356,11 @@ namespace llvm {
     /// printOffset - This is just convenient handler for printing offsets.
     void printOffset(int64_t Offset) const;
 
+    /// isBlockOnlyReachableByFallthough - Return true if the basic block has
+    /// exactly one predecessor and the control transfer mechanism between
+    /// the predecessor and this block is a fall-through.
+    virtual bool isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) const;
+
   private:
 
     /// processDebugLoc - Processes the debug information of each machine

include/llvm/CodeGen/MachineBasicBlock.h

@@ -285,11 +285,6 @@ 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;
-
   void pop_front() { Insts.pop_front(); }
   void pop_back() { Insts.pop_back(); }
   void push_back(MachineInstr *MI) { Insts.push_back(MI); }

lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -1717,7 +1717,7 @@ void AsmPrinter::EmitBasicBlockStart(const MachineBasicBlock *MBB) const {
   }
 
   // Print the main label for the block.
-  if (MBB->pred_empty() || MBB->isOnlyReachableByFallthrough()) {
+  if (MBB->pred_empty() || isBlockOnlyReachableByFallthrough(MBB)) {
     if (VerboseAsm) {
       // NOTE: Want this comment at start of line.
       O << MAI->getCommentString() << " BB#" << MBB->getNumber() << ':';
@@ -1764,6 +1764,39 @@ void AsmPrinter::printOffset(int64_t Offset) const {
     O << Offset;
 }
 
+/// isBlockOnlyReachableByFallthough - Return true if the basic block has
+/// exactly one predecessor and the control transfer mechanism between
+/// the predecessor and this block is a fall-through.
+bool AsmPrinter::isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) 
+    const {
+  // If this is a landing pad, it isn't a fall through.  If it has no preds,
+  // then nothing falls through to it.
+  if (MBB->isLandingPad() || MBB->pred_empty())
+    return false;
+  
+  // If there isn't exactly one predecessor, it can't be a fall through.
+  MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(), PI2 = PI;
+  ++PI2;
+  if (PI2 != MBB->pred_end())
+    return false;
+  
+  // The predecessor has to be immediately before this block.
+  const MachineBasicBlock *Pred = *PI;
+  
+  if (!Pred->isLayoutSuccessor(MBB))
+    return false;
+  
+  // If the block is completely empty, then it definitely does fall through.
+  if (Pred->empty())
+    return true;
+  
+  // Otherwise, check the last instruction.
+  const MachineInstr &LastInst = Pred->back();
+  return !LastInst.getDesc().isBarrier();
+}
+
+
+
 GCMetadataPrinter *AsmPrinter::GetOrCreateGCPrinter(GCStrategy *S) {
   if (!S->usesMetadata())
     return 0;

lib/CodeGen/MachineBasicBlock.cpp

@@ -143,36 +143,6 @@ MachineBasicBlock::iterator MachineBasicBlock::getFirstTerminator() {
   return I;
 }
 
-/// 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 MachineBasicBlock::isOnlyReachableByFallthrough() const {
-  // If this is a landing pad, it isn't a fall through.  If it has no preds,
-  // then nothing falls through to it.
-  if (isLandingPad() || pred_empty())
-    return false;
-  
-  // If there isn't exactly one predecessor, it can't be a fall through.
-  const_pred_iterator PI = pred_begin(), PI2 = PI;
-  ++PI2;
-  if (PI2 != pred_end())
-    return false;
-  
-  // The predecessor has to be immediately before this block.
-  const MachineBasicBlock *Pred = *PI;
-  
-  if (!Pred->isLayoutSuccessor(this))
-    return false;
-  
-  // If the block is completely empty, then it definitely does fall through.
-  if (Pred->empty())
-    return true;
-  
-  // Otherwise, check the last instruction.
-  const MachineInstr &LastInst = Pred->back();
-  return !LastInst.getDesc().isBarrier();
-}
-
 void MachineBasicBlock::dump() const {
   print(dbgs());
 }

lib/Target/Sparc/AsmPrinter/SparcAsmPrinter.cpp

@@ -56,6 +56,9 @@ namespace {
                              unsigned AsmVariant, const char *ExtraCode);
 
     bool printGetPCX(const MachineInstr *MI, unsigned OpNo);
+    
+    virtual bool isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB)
+                       const;
   };
 } // end of anonymous namespace
 
@@ -197,6 +200,38 @@ bool SparcAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
   return false;
 }
 
+/// isBlockOnlyReachableByFallthough - Return true if the basic block has
+/// exactly one predecessor and the control transfer mechanism between
+/// the predecessor and this block is a fall-through.
+/// Override AsmPrinter implementation to handle delay slots
+bool SparcAsmPrinter::isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) 
+    const {
+  // If this is a landing pad, it isn't a fall through.  If it has no preds,
+  // then nothing falls through to it.
+  if (MBB->isLandingPad() || MBB->pred_empty())
+    return false;
+  
+  // If there isn't exactly one predecessor, it can't be a fall through.
+  MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(), PI2 = PI;
+  ++PI2;
+  if (PI2 != MBB->pred_end())
+    return false;
+  
+  // The predecessor has to be immediately before this block.
+  const MachineBasicBlock *Pred = *PI;
+  
+  if (!Pred->isLayoutSuccessor(MBB))
+    return false;
+  
+  // Check if the last terminator is an unconditional branch
+  MachineBasicBlock::const_iterator I = Pred->end();
+  while( I != Pred->begin() && !(--I)->getDesc().isTerminator() )
+      ; /* Noop */
+  return I == Pred->end() || !I->getDesc().isBarrier();
+}
+
+
+
 // Force static initialization.
 extern "C" void LLVMInitializeSparcAsmPrinter() { 
   RegisterAsmPrinter<SparcAsmPrinter> X(TheSparcTarget);

utils/TableGen/DAGISelEmitter.cpp

@@ -1975,7 +1975,7 @@ void DAGISelEmitter::run(raw_ostream &OS) {
   // definitions.  Emit the resultant instruction selector.
   EmitInstructionSelector(OS);  
   
-#if 0
+#if 1
   MatcherNode *Matcher = 0;
   // Walk the patterns backwards, building a matcher for each and adding it to
   // the matcher for the whole target.