AllocationOrder.h revision 314564 
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
35public:
36  /// Create a new AllocationOrder for VirtReg.
37  /// @param VirtReg      Virtual register to allocate for.
38  /// @param VRM          Virtual register map for function.
39  /// @param RegClassInfo Information about reserved and allocatable registers.
40  AllocationOrder(unsigned VirtReg,
41                  const VirtRegMap &VRM,
42                  const RegisterClassInfo &RegClassInfo,
43                  const LiveRegMatrix *Matrix);
44
45  /// Get the allocation order without reordered hints.
46  ArrayRef<MCPhysReg> getOrder() const { return Order; }
47
48  /// Return the next physical register in the allocation order, or 0.
49  /// It is safe to call next() again after it returned 0, it will keep
50  /// returning 0 until rewind() is called.
51  unsigned next(unsigned Limit = 0) {
52    if (Pos < 0)
53      return Hints.end()[Pos++];
54    if (!Limit)
55      Limit = Order.size();
56    while (Pos < int(Limit)) {
57      unsigned Reg = Order[Pos++];
58      if (!isHint(Reg))
59        return Reg;
60    }
61    return 0;
62  }
63
64  /// As next(), but allow duplicates to be returned, and stop before the
65  /// Limit'th register in the RegisterClassInfo allocation order.
66  ///
67  /// This can produce more than Limit registers if there are hints.
68  unsigned nextWithDups(unsigned Limit) {
69    if (Pos < 0)
70      return Hints.end()[Pos++];
71    if (Pos < int(Limit))
72      return Order[Pos++];
73    return 0;
74  }
75
76  /// Start over from the beginning.
77  void rewind() { Pos = -int(Hints.size()); }
78
79  /// Return true if the last register returned from next() was a preferred register.
80  bool isHint() const { return Pos <= 0; }
81
82  /// Return true if PhysReg is a preferred register.
83  bool isHint(unsigned PhysReg) const { return is_contained(Hints, PhysReg); }
84};
85
86} // end namespace llvm
87
88#endif
89