RegAllocBase.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338 
1//===-- RegAllocBase.cpp - Register Allocator Base Class ------------------===//
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 defines the RegAllocBase class which provides common functionality
11// for LiveIntervalUnion-based register allocators.
12//
13//===----------------------------------------------------------------------===//
14
15#define DEBUG_TYPE "regalloc"
16#include "RegAllocBase.h"
17#include "Spiller.h"
18#include "llvm/ADT/Statistic.h"
19#include "llvm/CodeGen/LiveIntervalAnalysis.h"
20#include "llvm/CodeGen/LiveRangeEdit.h"
21#include "llvm/CodeGen/LiveRegMatrix.h"
22#include "llvm/CodeGen/MachineInstr.h"
23#include "llvm/CodeGen/MachineRegisterInfo.h"
24#include "llvm/CodeGen/VirtRegMap.h"
25#include "llvm/Target/TargetMachine.h"
26#include "llvm/Target/TargetRegisterInfo.h"
27#ifndef NDEBUG
28#include "llvm/ADT/SparseBitVector.h"
29#endif
30#include "llvm/Support/CommandLine.h"
31#include "llvm/Support/Debug.h"
32#include "llvm/Support/ErrorHandling.h"
33#include "llvm/Support/raw_ostream.h"
34#include "llvm/Support/Timer.h"
35
36using namespace llvm;
37
38STATISTIC(NumNewQueued    , "Number of new live ranges queued");
39
40// Temporary verification option until we can put verification inside
41// MachineVerifier.
42static cl::opt<bool, true>
43VerifyRegAlloc("verify-regalloc", cl::location(RegAllocBase::VerifyEnabled),
44               cl::desc("Verify during register allocation"));
45
46const char RegAllocBase::TimerGroupName[] = "Register Allocation";
47bool RegAllocBase::VerifyEnabled = false;
48
49//===----------------------------------------------------------------------===//
50//                         RegAllocBase Implementation
51//===----------------------------------------------------------------------===//
52
53// Pin the vtable to this file.
54void RegAllocBase::anchor() {}
55
56void RegAllocBase::init(VirtRegMap &vrm,
57                        LiveIntervals &lis,
58                        LiveRegMatrix &mat) {
59  TRI = &vrm.getTargetRegInfo();
60  MRI = &vrm.getRegInfo();
61  VRM = &vrm;
62  LIS = &lis;
63  Matrix = &mat;
64  MRI->freezeReservedRegs(vrm.getMachineFunction());
65  RegClassInfo.runOnMachineFunction(vrm.getMachineFunction());
66}
67
68// Visit all the live registers. If they are already assigned to a physical
69// register, unify them with the corresponding LiveIntervalUnion, otherwise push
70// them on the priority queue for later assignment.
71void RegAllocBase::seedLiveRegs() {
72  NamedRegionTimer T("Seed Live Regs", TimerGroupName, TimePassesIsEnabled);
73  for (unsigned i = 0, e = MRI->getNumVirtRegs(); i != e; ++i) {
74    unsigned Reg = TargetRegisterInfo::index2VirtReg(i);
75    if (MRI->reg_nodbg_empty(Reg))
76      continue;
77    enqueue(&LIS->getInterval(Reg));
78  }
79}
80
81// Top-level driver to manage the queue of unassigned VirtRegs and call the
82// selectOrSplit implementation.
83void RegAllocBase::allocatePhysRegs() {
84  seedLiveRegs();
85
86  // Continue assigning vregs one at a time to available physical registers.
87  while (LiveInterval *VirtReg = dequeue()) {
88    assert(!VRM->hasPhys(VirtReg->reg) && "Register already assigned");
89
90    // Unused registers can appear when the spiller coalesces snippets.
91    if (MRI->reg_nodbg_empty(VirtReg->reg)) {
92      DEBUG(dbgs() << "Dropping unused " << *VirtReg << '\n');
93      LIS->removeInterval(VirtReg->reg);
94      continue;
95    }
96
97    // Invalidate all interference queries, live ranges could have changed.
98    Matrix->invalidateVirtRegs();
99
100    // selectOrSplit requests the allocator to return an available physical
101    // register if possible and populate a list of new live intervals that
102    // result from splitting.
103    DEBUG(dbgs() << "\nselectOrSplit "
104          << MRI->getRegClass(VirtReg->reg)->getName()
105          << ':' << *VirtReg << " w=" << VirtReg->weight << '\n');
106    typedef SmallVector<unsigned, 4> VirtRegVec;
107    VirtRegVec SplitVRegs;
108    unsigned AvailablePhysReg = selectOrSplit(*VirtReg, SplitVRegs);
109
110    if (AvailablePhysReg == ~0u) {
111      // selectOrSplit failed to find a register!
112      // Probably caused by an inline asm.
113      MachineInstr *MI = 0;
114      for (MachineRegisterInfo::reg_instr_iterator
115           I = MRI->reg_instr_begin(VirtReg->reg), E = MRI->reg_instr_end();
116           I != E; ) {
117        MachineInstr *TmpMI = &*(I++);
118        if (TmpMI->isInlineAsm()) {
119          MI = TmpMI;
120          break;
121        }
122      }
123      if (MI)
124        MI->emitError("inline assembly requires more registers than available");
125      else
126        report_fatal_error("ran out of registers during register allocation");
127      // Keep going after reporting the error.
128      VRM->assignVirt2Phys(VirtReg->reg,
129                 RegClassInfo.getOrder(MRI->getRegClass(VirtReg->reg)).front());
130      continue;
131    }
132
133    if (AvailablePhysReg)
134      Matrix->assign(*VirtReg, AvailablePhysReg);
135
136    for (VirtRegVec::iterator I = SplitVRegs.begin(), E = SplitVRegs.end();
137         I != E; ++I) {
138      LiveInterval *SplitVirtReg = &LIS->getInterval(*I);
139      assert(!VRM->hasPhys(SplitVirtReg->reg) && "Register already assigned");
140      if (MRI->reg_nodbg_empty(SplitVirtReg->reg)) {
141        DEBUG(dbgs() << "not queueing unused  " << *SplitVirtReg << '\n');
142        LIS->removeInterval(SplitVirtReg->reg);
143        continue;
144      }
145      DEBUG(dbgs() << "queuing new interval: " << *SplitVirtReg << "\n");
146      assert(TargetRegisterInfo::isVirtualRegister(SplitVirtReg->reg) &&
147             "expect split value in virtual register");
148      enqueue(SplitVirtReg);
149      ++NumNewQueued;
150    }
151  }
152}
153