lib/CodeGen/AllocationOrder.h

   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
  24 namespace llvm {
  25
  26 class RegisterClassInfo;
  27 class VirtRegMap;
  28 class LiveRegMatrix;
  29
  30 class 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
  38 public:
  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