AllocationOrder.h revision 327952 
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/ADT/STLExtras.h"
22#include "llvm/MC/MCRegisterInfo.h"
23
24namespace llvm {
25
26class RegisterClassInfo;
27class VirtRegMap;
28class LiveRegMatrix;
29
30class LLVM_LIBRARY_VISIBILITY AllocationOrder {
31  SmallVector<MCPhysReg, 16> Hints;
32  ArrayRef<MCPhysReg> Order;
33  int Pos;
34
35  // If HardHints is true, *only* Hints will be returned.
36  bool HardHints;
37
38public:
39
40  /// Create a new AllocationOrder for VirtReg.
41  /// @param VirtReg      Virtual register to allocate for.
42  /// @param VRM          Virtual register map for function.
43  /// @param RegClassInfo Information about reserved and allocatable registers.
44  AllocationOrder(unsigned VirtReg,
45                  const VirtRegMap &VRM,
46                  const RegisterClassInfo &RegClassInfo,
47                  const LiveRegMatrix *Matrix);
48
49  /// Get the allocation order without reordered hints.
50  ArrayRef<MCPhysReg> getOrder() const { return Order; }
51
52  /// Return the next physical register in the allocation order, or 0.
53  /// It is safe to call next() again after it returned 0, it will keep
54  /// returning 0 until rewind() is called.
55  unsigned next(unsigned Limit = 0) {
56    if (Pos < 0)
57      return Hints.end()[Pos++];
58    if (HardHints)
59      return 0;
60    if (!Limit)
61      Limit = Order.size();
62    while (Pos < int(Limit)) {
63      unsigned Reg = Order[Pos++];
64      if (!isHint(Reg))
65        return Reg;
66    }
67    return 0;
68  }
69
70  /// As next(), but allow duplicates to be returned, and stop before the
71  /// Limit'th register in the RegisterClassInfo allocation order.
72  ///
73  /// This can produce more than Limit registers if there are hints.
74  unsigned nextWithDups(unsigned Limit) {
75    if (Pos < 0)
76      return Hints.end()[Pos++];
77    if (HardHints)
78      return 0;
79    if (Pos < int(Limit))
80      return Order[Pos++];
81    return 0;
82  }
83
84  /// Start over from the beginning.
85  void rewind() { Pos = -int(Hints.size()); }
86
87  /// Return true if the last register returned from next() was a preferred register.
88  bool isHint() const { return Pos <= 0; }
89
90  /// Return true if PhysReg is a preferred register.
91  bool isHint(unsigned PhysReg) const { return is_contained(Hints, PhysReg); }
92};
93
94} // end namespace llvm
95
96#endif
97