AllocationOrder.h revision 296417 
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_LIB_CODEGEN_ALLOCATIONORDER_H
18#define LLVM_LIB_CODEGEN_ALLOCATIONORDER_H
19
20#include "llvm/ADT/ArrayRef.h"
21#include "llvm/MC/MCRegisterInfo.h"
22
23namespace llvm {
24
25class RegisterClassInfo;
26class VirtRegMap;
27class LiveRegMatrix;
28
29class LLVM_LIBRARY_VISIBILITY AllocationOrder {
30  SmallVector<MCPhysReg, 16> Hints;
31  ArrayRef<MCPhysReg> Order;
32  int Pos;
33
34public:
35  /// Create a new AllocationOrder for VirtReg.
36  /// @param VirtReg      Virtual register to allocate for.
37  /// @param VRM          Virtual register map for function.
38  /// @param RegClassInfo Information about reserved and allocatable registers.
39  AllocationOrder(unsigned VirtReg,
40                  const VirtRegMap &VRM,
41                  const RegisterClassInfo &RegClassInfo,
42                  const LiveRegMatrix *Matrix);
43
44  /// Get the allocation order without reordered hints.
45  ArrayRef<MCPhysReg> getOrder() const { return Order; }
46
47  /// Return the next physical register in the allocation order, or 0.
48  /// It is safe to call next() again after it returned 0, it will keep
49  /// returning 0 until rewind() is called.
50  unsigned next(unsigned Limit = 0) {
51    if (Pos < 0)
52      return Hints.end()[Pos++];
53    if (!Limit)
54      Limit = Order.size();
55    while (Pos < int(Limit)) {
56      unsigned Reg = Order[Pos++];
57      if (!isHint(Reg))
58        return Reg;
59    }
60    return 0;
61  }
62
63  /// As next(), but allow duplicates to be returned, and stop before the
64  /// Limit'th register in the RegisterClassInfo allocation order.
65  ///
66  /// This can produce more than Limit registers if there are hints.
67  unsigned nextWithDups(unsigned Limit) {
68    if (Pos < 0)
69      return Hints.end()[Pos++];
70    if (Pos < int(Limit))
71      return Order[Pos++];
72    return 0;
73  }
74
75  /// Start over from the beginning.
76  void rewind() { Pos = -int(Hints.size()); }
77
78  /// Return true if the last register returned from next() was a preferred register.
79  bool isHint() const { return Pos <= 0; }
80
81  /// Return true if PhysReg is a preferred register.
82  bool isHint(unsigned PhysReg) const {
83    return std::find(Hints.begin(), Hints.end(), PhysReg) != Hints.end();
84  }
85};
86
87} // end namespace llvm
88
89#endif
90