LiveStackAnalysis.cpp revision 218893 
1//===-- LiveStackAnalysis.cpp - Live Stack Slot Analysis ------------------===//
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 live stack slot analysis pass. It is analogous to
11// live interval analysis except it's analyzing liveness of stack slots rather
12// than registers.
13//
14//===----------------------------------------------------------------------===//
15
16#define DEBUG_TYPE "livestacks"
17#include "llvm/CodeGen/LiveStackAnalysis.h"
18#include "llvm/CodeGen/LiveIntervalAnalysis.h"
19#include "llvm/CodeGen/Passes.h"
20#include "llvm/Target/TargetRegisterInfo.h"
21#include "llvm/Support/Debug.h"
22#include "llvm/Support/raw_ostream.h"
23#include "llvm/ADT/Statistic.h"
24#include <limits>
25using namespace llvm;
26
27char LiveStacks::ID = 0;
28INITIALIZE_PASS(LiveStacks, "livestacks",
29                "Live Stack Slot Analysis", false, false)
30
31char &llvm::LiveStacksID = LiveStacks::ID;
32
33void LiveStacks::getAnalysisUsage(AnalysisUsage &AU) const {
34  AU.setPreservesAll();
35  AU.addPreserved<SlotIndexes>();
36  AU.addRequiredTransitive<SlotIndexes>();
37  MachineFunctionPass::getAnalysisUsage(AU);
38}
39
40void LiveStacks::releaseMemory() {
41  // Release VNInfo memory regions, VNInfo objects don't need to be dtor'd.
42  VNInfoAllocator.Reset();
43  S2IMap.clear();
44  S2RCMap.clear();
45}
46
47bool LiveStacks::runOnMachineFunction(MachineFunction &) {
48  // FIXME: No analysis is being done right now. We are relying on the
49  // register allocators to provide the information.
50  return false;
51}
52
53LiveInterval &
54LiveStacks::getOrCreateInterval(int Slot, const TargetRegisterClass *RC) {
55  assert(Slot >= 0 && "Spill slot indice must be >= 0");
56  SS2IntervalMap::iterator I = S2IMap.find(Slot);
57  if (I == S2IMap.end()) {
58    I = S2IMap.insert(I, std::make_pair(Slot,
59            LiveInterval(TargetRegisterInfo::index2StackSlot(Slot), 0.0F)));
60    S2RCMap.insert(std::make_pair(Slot, RC));
61  } else {
62    // Use the largest common subclass register class.
63    const TargetRegisterClass *OldRC = S2RCMap[Slot];
64    S2RCMap[Slot] = getCommonSubClass(OldRC, RC);
65  }
66  return I->second;
67}
68
69/// print - Implement the dump method.
70void LiveStacks::print(raw_ostream &OS, const Module*) const {
71
72  OS << "********** INTERVALS **********\n";
73  for (const_iterator I = begin(), E = end(); I != E; ++I) {
74    I->second.print(OS);
75    int Slot = I->first;
76    const TargetRegisterClass *RC = getIntervalRegClass(Slot);
77    if (RC)
78      OS << " [" << RC->getName() << "]\n";
79    else
80      OS << " [Unknown]\n";
81  }
82}
83