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      1 //===- TargetRegisterInfo.cpp - Target Register Information Implementation ===//
      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 the TargetRegisterInfo interface.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "llvm/Target/TargetMachine.h"
     15 #include "llvm/Target/TargetRegisterInfo.h"
     16 #include "llvm/CodeGen/MachineFunction.h"
     17 #include "llvm/CodeGen/MachineFrameInfo.h"
     18 #include "llvm/ADT/BitVector.h"
     19 #include "llvm/Support/raw_ostream.h"
     20 
     21 using namespace llvm;
     22 
     23 TargetRegisterInfo::TargetRegisterInfo(const TargetRegisterInfoDesc *ID,
     24                              regclass_iterator RCB, regclass_iterator RCE,
     25                              const char *const *subregindexnames)
     26   : InfoDesc(ID), SubRegIndexNames(subregindexnames),
     27     RegClassBegin(RCB), RegClassEnd(RCE) {
     28 }
     29 
     30 TargetRegisterInfo::~TargetRegisterInfo() {}
     31 
     32 void PrintReg::print(raw_ostream &OS) const {
     33   if (!Reg)
     34     OS << "%noreg";
     35   else if (TargetRegisterInfo::isStackSlot(Reg))
     36     OS << "SS#" << TargetRegisterInfo::stackSlot2Index(Reg);
     37   else if (TargetRegisterInfo::isVirtualRegister(Reg))
     38     OS << "%vreg" << TargetRegisterInfo::virtReg2Index(Reg);
     39   else if (TRI && Reg < TRI->getNumRegs())
     40     OS << '%' << TRI->getName(Reg);
     41   else
     42     OS << "%physreg" << Reg;
     43   if (SubIdx) {
     44     if (TRI)
     45       OS << ':' << TRI->getSubRegIndexName(SubIdx);
     46     else
     47       OS << ":sub(" << SubIdx << ')';
     48   }
     49 }
     50 
     51 /// getMinimalPhysRegClass - Returns the Register Class of a physical
     52 /// register of the given type, picking the most sub register class of
     53 /// the right type that contains this physreg.
     54 const TargetRegisterClass *
     55 TargetRegisterInfo::getMinimalPhysRegClass(unsigned reg, EVT VT) const {
     56   assert(isPhysicalRegister(reg) && "reg must be a physical register");
     57 
     58   // Pick the most sub register class of the right type that contains
     59   // this physreg.
     60   const TargetRegisterClass* BestRC = 0;
     61   for (regclass_iterator I = regclass_begin(), E = regclass_end(); I != E; ++I){
     62     const TargetRegisterClass* RC = *I;
     63     if ((VT == MVT::Other || RC->hasType(VT)) && RC->contains(reg) &&
     64         (!BestRC || BestRC->hasSubClass(RC)))
     65       BestRC = RC;
     66   }
     67 
     68   assert(BestRC && "Couldn't find the register class");
     69   return BestRC;
     70 }
     71 
     72 /// getAllocatableSetForRC - Toggle the bits that represent allocatable
     73 /// registers for the specific register class.
     74 static void getAllocatableSetForRC(const MachineFunction &MF,
     75                                    const TargetRegisterClass *RC, BitVector &R){
     76   ArrayRef<unsigned> Order = RC->getRawAllocationOrder(MF);
     77   for (unsigned i = 0; i != Order.size(); ++i)
     78     R.set(Order[i]);
     79 }
     80 
     81 BitVector TargetRegisterInfo::getAllocatableSet(const MachineFunction &MF,
     82                                           const TargetRegisterClass *RC) const {
     83   BitVector Allocatable(getNumRegs());
     84   if (RC) {
     85     getAllocatableSetForRC(MF, RC, Allocatable);
     86   } else {
     87     for (TargetRegisterInfo::regclass_iterator I = regclass_begin(),
     88          E = regclass_end(); I != E; ++I)
     89       if ((*I)->isAllocatable())
     90         getAllocatableSetForRC(MF, *I, Allocatable);
     91   }
     92 
     93   // Mask out the reserved registers
     94   BitVector Reserved = getReservedRegs(MF);
     95   Allocatable &= Reserved.flip();
     96 
     97   return Allocatable;
     98 }
     99 
    100 const TargetRegisterClass *
    101 llvm::getCommonSubClass(const TargetRegisterClass *A,
    102                         const TargetRegisterClass *B) {
    103   // First take care of the trivial cases
    104   if (A == B)
    105     return A;
    106   if (!A || !B)
    107     return 0;
    108 
    109   // If B is a subclass of A, it will be handled in the loop below
    110   if (B->hasSubClass(A))
    111     return A;
    112 
    113   const TargetRegisterClass *Best = 0;
    114   for (TargetRegisterClass::sc_iterator I = A->subclasses_begin();
    115        const TargetRegisterClass *X = *I; ++I) {
    116     if (X == B)
    117       return B;                 // B is a subclass of A
    118 
    119     // X must be a common subclass of A and B
    120     if (!B->hasSubClass(X))
    121       continue;
    122 
    123     // A superclass is definitely better.
    124     if (!Best || Best->hasSuperClass(X)) {
    125       Best = X;
    126       continue;
    127     }
    128 
    129     // A subclass is definitely worse
    130     if (Best->hasSubClass(X))
    131       continue;
    132 
    133     // Best and *I have no super/sub class relation - pick the larger class, or
    134     // the smaller spill size.
    135     int nb = std::distance(Best->begin(), Best->end());
    136     int ni = std::distance(X->begin(), X->end());
    137     if (ni>nb || (ni==nb && X->getSize() < Best->getSize()))
    138       Best = X;
    139   }
    140   return Best;
    141 }
    142