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/Config/llvm-config.h"
16 #include "llvm/IR/BasicBlock.h"
17 #include "llvm/IR/CFG.h"
18 #include "llvm/IR/Instruction.h"
19 #include "llvm/IR/Instructions.h"
20 #include "llvm/IR/IntrinsicInst.h"
21 #include "llvm/IR/Intrinsics.h"
22 #include "llvm/IR/User.h"
23 #include "llvm/Support/Casting.h"
24 #include "llvm/Support/CommandLine.h"
25 #include "llvm/Support/Compiler.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Support/raw_ostream.h"
33 using namespace llvm::safestack;
35 #define DEBUG_TYPE "safestackcoloring"
37 // Disabled by default due to PR32143.
38 static cl::opt<bool> ClColoring("safe-stack-coloring",
39 cl::desc("enable safe stack coloring"),
40 cl::Hidden, cl::init(false));
42 const StackColoring::LiveRange &StackColoring::getLiveRange(AllocaInst *AI) {
43 const auto IT = AllocaNumbering.find(AI);
44 assert(IT != AllocaNumbering.end());
45 return LiveRanges[IT->second];
48 bool StackColoring::readMarker(Instruction *I, bool *IsStart) {
49 if (!I->isLifetimeStartOrEnd())
52 auto *II = cast<IntrinsicInst>(I);
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 LLVM_DEBUG(dbgs() << "Instructions:\n");
106 for (BasicBlock *BB : depth_first(&F)) {
107 LLVM_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 LLVM_DEBUG(dbgs() << " " << InstNo << ": "
125 << (M.IsStart ? "start " : "end ") << M.AllocaNo
126 << ", " << *I << "\n");
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 // If a predecessor is unreachable, ignore it.
175 if (I == BlockLiveness.end())
177 LocalLiveIn |= I->second.LiveOut;
180 // Compute LiveOut by subtracting out lifetimes that end in this
181 // block, then adding in lifetimes that begin in this block. If
182 // we have both BEGIN and END markers in the same basic block
183 // then we know that the BEGIN marker comes after the END,
184 // because we already handle the case where the BEGIN comes
185 // before the END when collecting the markers (and building the
186 // BEGIN/END vectors).
187 BitVector LocalLiveOut = LocalLiveIn;
188 LocalLiveOut.reset(BlockInfo.End);
189 LocalLiveOut |= BlockInfo.Begin;
191 // Update block LiveIn set, noting whether it has changed.
192 if (LocalLiveIn.test(BlockInfo.LiveIn)) {
194 BlockInfo.LiveIn |= LocalLiveIn;
197 // Update block LiveOut set, noting whether it has changed.
198 if (LocalLiveOut.test(BlockInfo.LiveOut)) {
200 BlockInfo.LiveOut |= LocalLiveOut;
206 void StackColoring::calculateLiveIntervals() {
207 for (auto IT : BlockLiveness) {
208 BasicBlock *BB = IT.getFirst();
209 BlockLifetimeInfo &BlockInfo = IT.getSecond();
210 unsigned BBStart, BBEnd;
211 std::tie(BBStart, BBEnd) = BlockInstRange[BB];
213 BitVector Started, Ended;
214 Started.resize(NumAllocas);
215 Ended.resize(NumAllocas);
216 SmallVector<unsigned, 8> Start;
217 Start.resize(NumAllocas);
219 // LiveIn ranges start at the first instruction.
220 for (unsigned AllocaNo = 0; AllocaNo < NumAllocas; ++AllocaNo) {
221 if (BlockInfo.LiveIn.test(AllocaNo)) {
222 Started.set(AllocaNo);
223 Start[AllocaNo] = BBStart;
227 for (auto &It : BBMarkers[BB]) {
228 unsigned InstNo = It.first;
229 bool IsStart = It.second.IsStart;
230 unsigned AllocaNo = It.second.AllocaNo;
233 assert(!Started.test(AllocaNo) || Start[AllocaNo] == BBStart);
234 if (!Started.test(AllocaNo)) {
235 Started.set(AllocaNo);
236 Ended.reset(AllocaNo);
237 Start[AllocaNo] = InstNo;
240 assert(!Ended.test(AllocaNo));
241 if (Started.test(AllocaNo)) {
242 LiveRanges[AllocaNo].AddRange(Start[AllocaNo], InstNo);
243 Started.reset(AllocaNo);
249 for (unsigned AllocaNo = 0; AllocaNo < NumAllocas; ++AllocaNo)
250 if (Started.test(AllocaNo))
251 LiveRanges[AllocaNo].AddRange(Start[AllocaNo], BBEnd);
255 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
256 LLVM_DUMP_METHOD void StackColoring::dumpAllocas() {
257 dbgs() << "Allocas:\n";
258 for (unsigned AllocaNo = 0; AllocaNo < NumAllocas; ++AllocaNo)
259 dbgs() << " " << AllocaNo << ": " << *Allocas[AllocaNo] << "\n";
262 LLVM_DUMP_METHOD void StackColoring::dumpBlockLiveness() {
263 dbgs() << "Block liveness:\n";
264 for (auto IT : BlockLiveness) {
265 BasicBlock *BB = IT.getFirst();
266 BlockLifetimeInfo &BlockInfo = BlockLiveness[BB];
267 auto BlockRange = BlockInstRange[BB];
268 dbgs() << " BB [" << BlockRange.first << ", " << BlockRange.second
269 << "): begin " << BlockInfo.Begin << ", end " << BlockInfo.End
270 << ", livein " << BlockInfo.LiveIn << ", liveout "
271 << BlockInfo.LiveOut << "\n";
275 LLVM_DUMP_METHOD void StackColoring::dumpLiveRanges() {
276 dbgs() << "Alloca liveness:\n";
277 for (unsigned AllocaNo = 0; AllocaNo < NumAllocas; ++AllocaNo) {
278 LiveRange &Range = LiveRanges[AllocaNo];
279 dbgs() << " " << AllocaNo << ": " << Range << "\n";
284 void StackColoring::run() {
285 LLVM_DEBUG(dumpAllocas());
287 for (unsigned I = 0; I < NumAllocas; ++I)
288 AllocaNumbering[Allocas[I]] = I;
289 LiveRanges.resize(NumAllocas);
294 for (auto &R : LiveRanges) {
301 for (auto &R : LiveRanges)
302 R.SetMaximum(NumInst);
303 for (unsigned I = 0; I < NumAllocas; ++I)
304 if (!InterestingAllocas.test(I))
305 LiveRanges[I] = getFullLiveRange();
307 calculateLocalLiveness();
308 LLVM_DEBUG(dumpBlockLiveness());
309 calculateLiveIntervals();
310 LLVM_DEBUG(dumpLiveRanges());