Added TargetRegisterInfo::getAllocatableClass.

The ensures that virtual registers always belong to an allocatable class.
If your target attempts to create a vreg for an operand that has no
allocatable register subclass, you will crash quickly.

This ensures that targets define register classes as intended.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156046 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetRegisterInfo.h

@@ -301,6 +301,11 @@ public:
   const TargetRegisterClass *
     getMinimalPhysRegClass(unsigned Reg, EVT VT = MVT::Other) const;
 
+  /// getAllocatableClass - Return the maximal subclass of the given register
+  /// class that is alloctable, or NULL.
+  const TargetRegisterClass *
+    getAllocatableClass(const TargetRegisterClass *RC) const;
+
   /// getAllocatableSet - Returns a bitset indexed by register number
   /// indicating if a register is allocatable or not. If a register class is
   /// specified, returns the subset for the class.

lib/CodeGen/SelectionDAG/InstrEmitter.cpp

@@ -114,8 +114,10 @@ EmitCopyFromReg(SDNode *Node, unsigned ResNo, bool IsClone, bool IsCloned,
           if (User->isMachineOpcode()) {
             const MCInstrDesc &II = TII->get(User->getMachineOpcode());
             const TargetRegisterClass *RC = 0;
-            if (i+II.getNumDefs() < II.getNumOperands())
-              RC = TII->getRegClass(II, i+II.getNumDefs(), TRI);
+            if (i+II.getNumDefs() < II.getNumOperands()) {
+              RC = TRI->getAllocatableClass(
+                TII->getRegClass(II, i+II.getNumDefs(), TRI));
+            }
             if (!UseRC)
               UseRC = RC;
             else if (RC) {
@@ -196,7 +198,8 @@ void InstrEmitter::CreateVirtualRegisters(SDNode *Node, MachineInstr *MI,
     // is a vreg in the same register class, use the CopyToReg'd destination
     // register instead of creating a new vreg.
     unsigned VRBase = 0;
-    const TargetRegisterClass *RC = TII->getRegClass(II, i, TRI);
+    const TargetRegisterClass *RC =
+      TRI->getAllocatableClass(TII->getRegClass(II, i, TRI));
     if (II.OpInfo[i].isOptionalDef()) {
       // Optional def must be a physical register.
       unsigned NumResults = CountResults(Node);
@@ -293,7 +296,7 @@ InstrEmitter::AddRegisterOperand(MachineInstr *MI, SDValue Op,
   if (II) {
     const TargetRegisterClass *DstRC = 0;
     if (IIOpNum < II->getNumOperands())
-      DstRC = TII->getRegClass(*II, IIOpNum, TRI);
+      DstRC = TRI->getAllocatableClass(TII->getRegClass(*II, IIOpNum, TRI));
     assert((DstRC || (MI->isVariadic() && IIOpNum >= MCID.getNumOperands())) &&
            "Don't have operand info for this instruction!");
     if (DstRC && !MRI->constrainRegClass(VReg, DstRC, MinRCSize)) {
@@ -548,7 +551,8 @@ InstrEmitter::EmitCopyToRegClassNode(SDNode *Node,
 
   // Create the new VReg in the destination class and emit a copy.
   unsigned DstRCIdx = cast<ConstantSDNode>(Node->getOperand(1))->getZExtValue();
-  const TargetRegisterClass *DstRC = TRI->getRegClass(DstRCIdx);
+  const TargetRegisterClass *DstRC =
+    TRI->getAllocatableClass(TRI->getRegClass(DstRCIdx));
   unsigned NewVReg = MRI->createVirtualRegister(DstRC);
   BuildMI(*MBB, InsertPos, Node->getDebugLoc(), TII->get(TargetOpcode::COPY),
     NewVReg).addReg(VReg);
@@ -566,7 +570,7 @@ void InstrEmitter::EmitRegSequence(SDNode *Node,
                                   bool IsClone, bool IsCloned) {
   unsigned DstRCIdx = cast<ConstantSDNode>(Node->getOperand(0))->getZExtValue();
   const TargetRegisterClass *RC = TRI->getRegClass(DstRCIdx);
-  unsigned NewVReg = MRI->createVirtualRegister(RC);
+  unsigned NewVReg = MRI->createVirtualRegister(TRI->getAllocatableClass(RC));
   MachineInstr *MI = BuildMI(*MF, Node->getDebugLoc(),
                              TII->get(TargetOpcode::REG_SEQUENCE), NewVReg);
   unsigned NumOps = Node->getNumOperands();

lib/CodeGen/TwoAddressInstructionPass.cpp

@@ -1298,7 +1298,8 @@ TryInstructionTransform(MachineBasicBlock::iterator &mi,
         // Unfold the load.
         DEBUG(dbgs() << "2addr:   UNFOLDING: " << MI);
         const TargetRegisterClass *RC =
-          TII->getRegClass(UnfoldMCID, LoadRegIndex, TRI);
+          TRI->getAllocatableClass(
+            TII->getRegClass(UnfoldMCID, LoadRegIndex, TRI));
         unsigned Reg = MRI->createVirtualRegister(RC);
         SmallVector<MachineInstr *, 2> NewMIs;
         if (!TII->unfoldMemoryOperand(MF, &MI, Reg,

lib/Target/TargetRegisterInfo.cpp

@@ -46,6 +46,29 @@ void PrintReg::print(raw_ostream &OS) const {
   }
 }
 
+/// getAllocatableClass - Return the maximal subclass of the given register
+/// class that is alloctable, or NULL.
+const TargetRegisterClass *
+TargetRegisterInfo::getAllocatableClass(const TargetRegisterClass *RC) const {
+  if (!RC || RC->isAllocatable())
+    return RC;
+
+  const unsigned *SubClass = RC->getSubClassMask();
+  for (unsigned Base = 0, BaseE = getNumRegClasses();
+       Base < BaseE; Base += 32) {
+    unsigned Idx = Base;
+    for (unsigned Mask = *SubClass++; Mask; Mask >>= 1) {
+      unsigned Offset = CountTrailingZeros_32(Mask);
+      const TargetRegisterClass *SubRC = getRegClass(Idx + Offset);
+      if (SubRC->isAllocatable())
+        return SubRC;
+      Mask >>= Offset;
+      Idx += Offset + 1;
+    }
+  }
+  return NULL;
+}
+
 /// getMinimalPhysRegClass - Returns the Register Class of a physical
 /// register of the given type, picking the most sub register class of
 /// the right type that contains this physreg.
@@ -71,6 +94,7 @@ TargetRegisterInfo::getMinimalPhysRegClass(unsigned reg, EVT VT) const {
 /// registers for the specific register class.
 static void getAllocatableSetForRC(const MachineFunction &MF,
                                    const TargetRegisterClass *RC, BitVector &R){
+  assert(RC->isAllocatable() && "invalid for nonallocatable sets");
   ArrayRef<uint16_t> Order = RC->getRawAllocationOrder(MF);
   for (unsigned i = 0; i != Order.size(); ++i)
     R.set(Order[i]);
@@ -80,7 +104,10 @@ BitVector TargetRegisterInfo::getAllocatableSet(const MachineFunction &MF,
                                           const TargetRegisterClass *RC) const {
   BitVector Allocatable(getNumRegs());
   if (RC) {
-    getAllocatableSetForRC(MF, RC, Allocatable);
+    // A register class with no allocatable subclass returns an empty set.
+    const TargetRegisterClass *SubClass = getAllocatableClass(RC);
+    if (SubClass)
+      getAllocatableSetForRC(MF, SubClass, Allocatable);
   } else {
     for (TargetRegisterInfo::regclass_iterator I = regclass_begin(),
          E = regclass_end(); I != E; ++I)