Add TargetRegisterInfo::getRawAllocationOrder().

This virtual function will replace allocation_order_begin/end as the one
to override when implementing custom allocation orders. It is simpler to
have one function return an ArrayRef than having two virtual functions
computing different ends of the same array.

Use getRawAllocationOrder() in place of allocation_order_begin() where
it makes sense, but leave some clients that look like they really want
the filtered allocation orders from RegisterClassInfo.

llvm-svn: 133170

llvm/include/llvm/Target/TargetRegisterInfo.h

@@ -18,6 +18,7 @@
 
 #include "llvm/CodeGen/MachineBasicBlock.h"
 #include "llvm/CodeGen/ValueTypes.h"
+#include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseSet.h"
 #include <cassert>
 #include <functional>
@@ -259,6 +260,27 @@ public:
     return end();
   }
 
+  /// getRawAllocationOrder - Returns the preferred order for allocating
+  /// registers from this register class in MF. The raw order comes directly
+  /// from the .td file and may include reserved registers that are not
+  /// allocatable. Register allocators should also make sure to allocate
+  /// callee-saved registers only after all the volatiles are used. The
+  /// RegisterClassInfo class provides filtered allocation orders with
+  /// callee-saved registers moved to the end.
+  ///
+  /// The MachineFunction argument can be used to tune the allocatable
+  /// registers based on the characteristics of the function, subtarget, or
+  /// other criteria.
+  ///
+  /// By default, this method returns all registers in the class.
+  ///
+  virtual
+  ArrayRef<unsigned> getRawAllocationOrder(const MachineFunction &MF) const {
+    iterator B = allocation_order_begin(MF);
+    iterator E = allocation_order_end(MF);
+    return ArrayRef<unsigned>(B, E - B);
+  }
+
   /// getSize - Return the size of the register in bytes, which is also the size
   /// of a stack slot allocated to hold a spilled copy of this register.
   unsigned getSize() const { return RegSize; }

llvm/lib/CodeGen/RegisterClassInfo.cpp

@@ -81,11 +81,9 @@ void RegisterClassInfo::compute(const TargetRegisterClass *RC) const {
 
   // FIXME: Once targets reserve registers instead of removing them from the
   // allocation order, we can simply use begin/end here.
-  TargetRegisterClass::iterator AOB = RC->allocation_order_begin(*MF);
-  TargetRegisterClass::iterator AOE = RC->allocation_order_end(*MF);
-
-  for (TargetRegisterClass::iterator I = AOB; I != AOE; ++I) {
-    unsigned PhysReg = *I;
+  ArrayRef<unsigned> RawOrder = RC->getRawAllocationOrder(*MF);
+  for (unsigned i = 0; i != RawOrder.size(); ++i) {
+    unsigned PhysReg = RawOrder[i];
     // Remove reserved registers from the allocation order.
     if (Reserved.test(PhysReg))
       continue;

llvm/lib/CodeGen/RenderMachineFunction.cpp

@@ -434,8 +434,7 @@ namespace llvm {
            rcEnd = tri->regclass_end();
          rcItr != rcEnd; ++rcItr) {
       const TargetRegisterClass *trc = *rcItr;
-      unsigned capacity = std::distance(trc->allocation_order_begin(*mf),
-                                        trc->allocation_order_end(*mf));
+      unsigned capacity = trc->getRawAllocationOrder(*mf).size();
 
       if (capacity != 0)
         capacityMap[trc] = capacity;
@@ -482,8 +481,7 @@ namespace llvm {
                rcItr != rcEnd; ++rcItr) {
             const TargetRegisterClass *trc = *rcItr;
 
-            if (trc->allocation_order_begin(*mf) ==
-                trc->allocation_order_end(*mf))
+            if (trc->getRawAllocationOrder(*mf).empty())
               continue;
 
             unsigned worstAtI = getWorst(li->reg, trc);

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -5429,6 +5429,8 @@ isAllocatableRegister(unsigned Reg, MachineFunction &MF,
     EVT ThisVT = MVT::Other;
 
     const TargetRegisterClass *RC = *RCI;
+    if (!RC->isAllocatable())
+      continue;
     // If none of the value types for this register class are valid, we
     // can't use it.  For example, 64-bit reg classes on 32-bit targets.
     for (TargetRegisterClass::vt_iterator I = RC->vt_begin(), E = RC->vt_end();
@@ -5450,15 +5452,14 @@ isAllocatableRegister(unsigned Reg, MachineFunction &MF,
     // frame pointer in functions that need it (due to them not being taken
     // out of allocation, because a variable sized allocation hasn't been seen
     // yet).  This is a slight code pessimization, but should still work.
-    for (TargetRegisterClass::iterator I = RC->allocation_order_begin(MF),
-         E = RC->allocation_order_end(MF); I != E; ++I)
-      if (*I == Reg) {
-        // We found a matching register class.  Keep looking at others in case
-        // we find one with larger registers that this physreg is also in.
-        FoundRC = RC;
-        FoundVT = ThisVT;
-        break;
-      }
+    ArrayRef<unsigned> RawOrder = RC->getRawAllocationOrder(MF);
+    if (std::find(RawOrder.begin(), RawOrder.end(), Reg) != RawOrder.end()) {
+      // We found a matching register class.  Keep looking at others in case
+      // we find one with larger registers that this physreg is also in.
+      FoundRC = RC;
+      FoundVT = ThisVT;
+      break;
+    }
   }
   return FoundRC;
 }
@@ -5605,9 +5606,15 @@ static void GetRegistersForValue(SelectionDAG &DAG,
                                             OpInfo.ConstraintVT);
 
   const TargetRegisterInfo *TRI = DAG.getTarget().getRegisterInfo();
+  BitVector Reserved = TRI->getReservedRegs(MF);
   unsigned NumAllocated = 0;
   for (unsigned i = 0, e = RegClassRegs.size(); i != e; ++i) {
     unsigned Reg = RegClassRegs[i];
+    // Filter out the reserved registers, but note that reserved registers are
+    // not fully determined at this point. We may still decide we need a frame
+    // pointer.
+    if (Reserved.test(Reg))
+      continue;
     // See if this register is available.
     if ((isOutReg && OutputRegs.count(Reg)) ||   // Already used.
         (isInReg  && InputRegs.count(Reg))) {    // Already used.