1 //===- SafeStackColoring.cpp - SafeStack frame coloring -------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #include "SafeStackColoring.h"
11 #include "llvm/ADT/BitVector.h"
12 #include "llvm/ADT/DenseMap.h"
13 #include "llvm/ADT/DepthFirstIterator.h"
14 #include "llvm/ADT/SmallVector.h"
15 #include "llvm/IR/BasicBlock.h"
16 #include "llvm/IR/CFG.h"
17 #include "llvm/IR/Instruction.h"
18 #include "llvm/IR/Instructions.h"
19 #include "llvm/IR/IntrinsicInst.h"
20 #include "llvm/IR/Intrinsics.h"
21 #include "llvm/IR/User.h"
22 #include "llvm/Support/Casting.h"
23 #include "llvm/Support/CommandLine.h"
24 #include "llvm/Support/Compiler.h"
25 #include "llvm/Support/Debug.h"
26 #include "llvm/Support/raw_ostream.h"
32 using namespace llvm::safestack;
34 #define DEBUG_TYPE "safestackcoloring"
36 // Disabled by default due to PR32143.
37 static cl::opt<bool> ClColoring("safe-stack-coloring",
38 cl::desc("enable safe stack coloring"),
39 cl::Hidden, cl::init(false));
41 const StackColoring::LiveRange &StackColoring::getLiveRange(AllocaInst *AI) {
42 const auto IT = AllocaNumbering.find(AI);
43 assert(IT != AllocaNumbering.end());
44 return LiveRanges[IT->second];
47 bool StackColoring::readMarker(Instruction *I, bool *IsStart) {
48 auto *II = dyn_cast<IntrinsicInst>(I);
49 if (!II || (II->getIntrinsicID() != Intrinsic::lifetime_start &&
50 II->getIntrinsicID() != Intrinsic::lifetime_end))
53 *IsStart = II->getIntrinsicID() == Intrinsic::lifetime_start;
57 void StackColoring::removeAllMarkers() {
58 for (auto *I : Markers) {
59 auto *Op = dyn_cast<Instruction>(I->getOperand(1));
61 // Remove the operand bitcast, too, if it has no more uses left.
62 if (Op && Op->use_empty())
63 Op->eraseFromParent();
67 void StackColoring::collectMarkers() {
68 InterestingAllocas.resize(NumAllocas);
69 DenseMap<BasicBlock *, SmallDenseMap<Instruction *, Marker>> BBMarkerSet;
71 // Compute the set of start/end markers per basic block.
72 for (unsigned AllocaNo = 0; AllocaNo < NumAllocas; ++AllocaNo) {
73 AllocaInst *AI = Allocas[AllocaNo];
74 SmallVector<Instruction *, 8> WorkList;
75 WorkList.push_back(AI);
76 while (!WorkList.empty()) {
77 Instruction *I = WorkList.pop_back_val();
78 for (User *U : I->users()) {
79 if (auto *BI = dyn_cast<BitCastInst>(U)) {
80 WorkList.push_back(BI);
83 auto *UI = dyn_cast<Instruction>(U);
87 if (!readMarker(UI, &IsStart))
90 InterestingAllocas.set(AllocaNo);
91 BBMarkerSet[UI->getParent()][UI] = {AllocaNo, IsStart};
92 Markers.push_back(UI);
97 // Compute instruction numbering. Only the following instructions are
99 // * Basic block entries
100 // * Lifetime markers
101 // For each basic block, compute
102 // * the list of markers in the instruction order
103 // * the sets of allocas whose lifetime starts or ends in this BB
104 DEBUG(dbgs() << "Instructions:\n");
106 for (BasicBlock *BB : depth_first(&F)) {
107 DEBUG(dbgs() << " " << InstNo << ": BB " << BB->getName() << "\n");
108 unsigned BBStart = InstNo++;
110 BlockLifetimeInfo &BlockInfo = BlockLiveness[BB];
111 BlockInfo.Begin.resize(NumAllocas);
112 BlockInfo.End.resize(NumAllocas);
113 BlockInfo.LiveIn.resize(NumAllocas);
114 BlockInfo.LiveOut.resize(NumAllocas);
116 auto &BlockMarkerSet = BBMarkerSet[BB];
117 if (BlockMarkerSet.empty()) {
118 unsigned BBEnd = InstNo;
119 BlockInstRange[BB] = std::make_pair(BBStart, BBEnd);
123 auto ProcessMarker = [&](Instruction *I, const Marker &M) {
124 DEBUG(dbgs() << " " << InstNo << ": "
125 << (M.IsStart ? "start " : "end ") << M.AllocaNo << ", "
128 BBMarkers[BB].push_back({InstNo, M});
130 InstructionNumbering[I] = InstNo++;
133 if (BlockInfo.End.test(M.AllocaNo))
134 BlockInfo.End.reset(M.AllocaNo);
135 BlockInfo.Begin.set(M.AllocaNo);
137 if (BlockInfo.Begin.test(M.AllocaNo))
138 BlockInfo.Begin.reset(M.AllocaNo);
139 BlockInfo.End.set(M.AllocaNo);
143 if (BlockMarkerSet.size() == 1) {
144 ProcessMarker(BlockMarkerSet.begin()->getFirst(),
145 BlockMarkerSet.begin()->getSecond());
147 // Scan the BB to determine the marker order.
148 for (Instruction &I : *BB) {
149 auto It = BlockMarkerSet.find(&I);
150 if (It == BlockMarkerSet.end())
152 ProcessMarker(&I, It->getSecond());
156 unsigned BBEnd = InstNo;
157 BlockInstRange[BB] = std::make_pair(BBStart, BBEnd);
162 void StackColoring::calculateLocalLiveness() {
167 for (BasicBlock *BB : depth_first(&F)) {
168 BlockLifetimeInfo &BlockInfo = BlockLiveness[BB];
170 // Compute LiveIn by unioning together the LiveOut sets of all preds.
171 BitVector LocalLiveIn;
172 for (auto *PredBB : predecessors(BB)) {
173 LivenessMap::const_iterator I = BlockLiveness.find(PredBB);
174 assert(I != BlockLiveness.end() && "Predecessor not found");
175 LocalLiveIn |= I->second.LiveOut;
178 // Compute LiveOut by subtracting out lifetimes that end in this
179 // block, then adding in lifetimes that begin in this block. If
180 // we have both BEGIN and END markers in the same basic block
181 // then we know that the BEGIN marker comes after the END,
182 // because we already handle the case where the BEGIN comes
183 // before the END when collecting the markers (and building the
184 // BEGIN/END vectors).
185 BitVector LocalLiveOut = LocalLiveIn;
186 LocalLiveOut.reset(BlockInfo.End);
187 LocalLiveOut |= BlockInfo.Begin;
189 // Update block LiveIn set, noting whether it has changed.
190 if (LocalLiveIn.test(BlockInfo.LiveIn)) {
192 BlockInfo.LiveIn |= LocalLiveIn;
195 // Update block LiveOut set, noting whether it has changed.
196 if (LocalLiveOut.test(BlockInfo.LiveOut)) {
198 BlockInfo.LiveOut |= LocalLiveOut;
204 void StackColoring::calculateLiveIntervals() {
205 for (auto IT : BlockLiveness) {
206 BasicBlock *BB = IT.getFirst();
207 BlockLifetimeInfo &BlockInfo = IT.getSecond();
208 unsigned BBStart, BBEnd;
209 std::tie(BBStart, BBEnd) = BlockInstRange[BB];
211 BitVector Started, Ended;
212 Started.resize(NumAllocas);
213 Ended.resize(NumAllocas);
214 SmallVector<unsigned, 8> Start;
215 Start.resize(NumAllocas);
217 // LiveIn ranges start at the first instruction.
218 for (unsigned AllocaNo = 0; AllocaNo < NumAllocas; ++AllocaNo) {
219 if (BlockInfo.LiveIn.test(AllocaNo)) {
220 Started.set(AllocaNo);
221 Start[AllocaNo] = BBStart;
225 for (auto &It : BBMarkers[BB]) {
226 unsigned InstNo = It.first;
227 bool IsStart = It.second.IsStart;
228 unsigned AllocaNo = It.second.AllocaNo;
231 assert(!Started.test(AllocaNo) || Start[AllocaNo] == BBStart);
232 if (!Started.test(AllocaNo)) {
233 Started.set(AllocaNo);
234 Ended.reset(AllocaNo);
235 Start[AllocaNo] = InstNo;
238 assert(!Ended.test(AllocaNo));
239 if (Started.test(AllocaNo)) {
240 LiveRanges[AllocaNo].AddRange(Start[AllocaNo], InstNo);
241 Started.reset(AllocaNo);
247 for (unsigned AllocaNo = 0; AllocaNo < NumAllocas; ++AllocaNo)
248 if (Started.test(AllocaNo))
249 LiveRanges[AllocaNo].AddRange(Start[AllocaNo], BBEnd);
253 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
254 LLVM_DUMP_METHOD void StackColoring::dumpAllocas() {
255 dbgs() << "Allocas:\n";
256 for (unsigned AllocaNo = 0; AllocaNo < NumAllocas; ++AllocaNo)
257 dbgs() << " " << AllocaNo << ": " << *Allocas[AllocaNo] << "\n";
260 LLVM_DUMP_METHOD void StackColoring::dumpBlockLiveness() {
261 dbgs() << "Block liveness:\n";
262 for (auto IT : BlockLiveness) {
263 BasicBlock *BB = IT.getFirst();
264 BlockLifetimeInfo &BlockInfo = BlockLiveness[BB];
265 auto BlockRange = BlockInstRange[BB];
266 dbgs() << " BB [" << BlockRange.first << ", " << BlockRange.second
267 << "): begin " << BlockInfo.Begin << ", end " << BlockInfo.End
268 << ", livein " << BlockInfo.LiveIn << ", liveout "
269 << BlockInfo.LiveOut << "\n";
273 LLVM_DUMP_METHOD void StackColoring::dumpLiveRanges() {
274 dbgs() << "Alloca liveness:\n";
275 for (unsigned AllocaNo = 0; AllocaNo < NumAllocas; ++AllocaNo) {
276 LiveRange &Range = LiveRanges[AllocaNo];
277 dbgs() << " " << AllocaNo << ": " << Range << "\n";
282 void StackColoring::run() {
283 DEBUG(dumpAllocas());
285 for (unsigned I = 0; I < NumAllocas; ++I)
286 AllocaNumbering[Allocas[I]] = I;
287 LiveRanges.resize(NumAllocas);
292 for (auto &R : LiveRanges) {
299 for (auto &R : LiveRanges)
300 R.SetMaximum(NumInst);
301 for (unsigned I = 0; I < NumAllocas; ++I)
302 if (!InterestingAllocas.test(I))
303 LiveRanges[I] = getFullLiveRange();
305 calculateLocalLiveness();
306 DEBUG(dumpBlockLiveness());
307 calculateLiveIntervals();
308 DEBUG(dumpLiveRanges());