AllocationOrder.h revision f7999fe1cb2c2bdb0a4080efabb4743719ce45ca 
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
20#include "llvm/ADT/ArrayRef.h"
21#include "llvm/MC/MCRegisterInfo.h"
22
23namespace llvm {
24
25class RegisterClassInfo;
26class VirtRegMap;
27
28class AllocationOrder {
29  SmallVector<MCPhysReg, 16> Hints;
30  ArrayRef<MCPhysReg> Order;
31  int Pos;
32
33public:
34  /// 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  /// Return the next physical register in the allocation order, or 0.
43  /// It is safe to call next() again after it returned 0, it will keep
44  /// returning 0 until rewind() is called.
45  unsigned next() {
46    if (Pos < 0)
47      return Hints.end()[Pos++];
48    while (Pos < int(Order.size())) {
49      unsigned Reg = Order[Pos++];
50      if (!isHint(Reg))
51        return Reg;
52    }
53    return 0;
54  }
55
56  /// Start over from the beginning.
57  void rewind() { Pos = -int(Hints.size()); }
58
59  /// Return true if the last register returned from next() was a preferred register.
60  bool isHint() const { return Pos <= 0; }
61
62  /// Return true if PhysReg is a preferred register.
63  bool isHint(unsigned PhysReg) const {
64    return std::find(Hints.begin(), Hints.end(), PhysReg) != Hints.end();
65  }
66};
67
68} // end namespace llvm
69
70#endif
71