AllocationOrder.h revision 234353 
1//===-- llvm/CodeGen/AllocationOrder.h - Allocation Order -*- C++ -*-------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements an allocation order for virtual registers.
11//
12// The preferred allocation order for a virtual register depends on allocation
13// hints and target hooks. The AllocationOrder class encapsulates all of that.
14//
15//===----------------------------------------------------------------------===//
16
17#ifndef LLVM_CODEGEN_ALLOCATIONORDER_H
18#define LLVM_CODEGEN_ALLOCATIONORDER_H
19
20namespace llvm {
21
22class RegisterClassInfo;
23class VirtRegMap;
24
25class AllocationOrder {
26  const unsigned *Begin;
27  const unsigned *End;
28  const unsigned *Pos;
29  const RegisterClassInfo &RCI;
30  unsigned Hint;
31  bool OwnedBegin;
32public:
33
34  /// AllocationOrder - Create a new AllocationOrder for VirtReg.
35  /// @param VirtReg      Virtual register to allocate for.
36  /// @param VRM          Virtual register map for function.
37  /// @param RegClassInfo Information about reserved and allocatable registers.
38  AllocationOrder(unsigned VirtReg,
39                  const VirtRegMap &VRM,
40                  const RegisterClassInfo &RegClassInfo);
41
42  ~AllocationOrder();
43
44  /// next - Return the next physical register in the allocation order, or 0.
45  /// It is safe to call next again after it returned 0.
46  /// It will keep returning 0 until rewind() is called.
47  unsigned next() {
48    // First take the hint.
49    if (!Pos) {
50      Pos = Begin;
51      if (Hint)
52        return Hint;
53    }
54    // Then look at the order from TRI.
55    while (Pos != End) {
56      unsigned Reg = *Pos++;
57      if (Reg != Hint)
58        return Reg;
59    }
60    return 0;
61  }
62
63  /// rewind - Start over from the beginning.
64  void rewind() { Pos = 0; }
65
66  /// isHint - Return true if PhysReg is a preferred register.
67  bool isHint(unsigned PhysReg) const { return PhysReg == Hint; }
68};
69
70} // end namespace llvm
71
72#endif
73