1 //===- ThreadSafetyTIL.cpp ------------------------------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT in the llvm repository for details.
7 //
8 //===----------------------------------------------------------------------===//
9
10 #include "clang/Analysis/Analyses/ThreadSafetyTIL.h"
11 #include "clang/Basic/LLVM.h"
12 #include "llvm/Support/Casting.h"
13 #include <cassert>
14 #include <cstddef>
15
16 using namespace clang;
17 using namespace threadSafety;
18 using namespace til;
19
getUnaryOpcodeString(TIL_UnaryOpcode Op)20 StringRef til::getUnaryOpcodeString(TIL_UnaryOpcode Op) {
21 switch (Op) {
22 case UOP_Minus: return "-";
23 case UOP_BitNot: return "~";
24 case UOP_LogicNot: return "!";
25 }
26 return {};
27 }
28
getBinaryOpcodeString(TIL_BinaryOpcode Op)29 StringRef til::getBinaryOpcodeString(TIL_BinaryOpcode Op) {
30 switch (Op) {
31 case BOP_Mul: return "*";
32 case BOP_Div: return "/";
33 case BOP_Rem: return "%";
34 case BOP_Add: return "+";
35 case BOP_Sub: return "-";
36 case BOP_Shl: return "<<";
37 case BOP_Shr: return ">>";
38 case BOP_BitAnd: return "&";
39 case BOP_BitXor: return "^";
40 case BOP_BitOr: return "|";
41 case BOP_Eq: return "==";
42 case BOP_Neq: return "!=";
43 case BOP_Lt: return "<";
44 case BOP_Leq: return "<=";
45 case BOP_Cmp: return "<=>";
46 case BOP_LogicAnd: return "&&";
47 case BOP_LogicOr: return "||";
48 }
49 return {};
50 }
51
force()52 SExpr* Future::force() {
53 Status = FS_evaluating;
54 Result = compute();
55 Status = FS_done;
56 return Result;
57 }
58
addPredecessor(BasicBlock * Pred)59 unsigned BasicBlock::addPredecessor(BasicBlock *Pred) {
60 unsigned Idx = Predecessors.size();
61 Predecessors.reserveCheck(1, Arena);
62 Predecessors.push_back(Pred);
63 for (auto *E : Args) {
64 if (auto *Ph = dyn_cast<Phi>(E)) {
65 Ph->values().reserveCheck(1, Arena);
66 Ph->values().push_back(nullptr);
67 }
68 }
69 return Idx;
70 }
71
reservePredecessors(unsigned NumPreds)72 void BasicBlock::reservePredecessors(unsigned NumPreds) {
73 Predecessors.reserve(NumPreds, Arena);
74 for (auto *E : Args) {
75 if (auto *Ph = dyn_cast<Phi>(E)) {
76 Ph->values().reserve(NumPreds, Arena);
77 }
78 }
79 }
80
81 // If E is a variable, then trace back through any aliases or redundant
82 // Phi nodes to find the canonical definition.
getCanonicalVal(const SExpr * E)83 const SExpr *til::getCanonicalVal(const SExpr *E) {
84 while (true) {
85 if (const auto *V = dyn_cast<Variable>(E)) {
86 if (V->kind() == Variable::VK_Let) {
87 E = V->definition();
88 continue;
89 }
90 }
91 if (const auto *Ph = dyn_cast<Phi>(E)) {
92 if (Ph->status() == Phi::PH_SingleVal) {
93 E = Ph->values()[0];
94 continue;
95 }
96 }
97 break;
98 }
99 return E;
100 }
101
102 // If E is a variable, then trace back through any aliases or redundant
103 // Phi nodes to find the canonical definition.
104 // The non-const version will simplify incomplete Phi nodes.
simplifyToCanonicalVal(SExpr * E)105 SExpr *til::simplifyToCanonicalVal(SExpr *E) {
106 while (true) {
107 if (auto *V = dyn_cast<Variable>(E)) {
108 if (V->kind() != Variable::VK_Let)
109 return V;
110 // Eliminate redundant variables, e.g. x = y, or x = 5,
111 // but keep anything more complicated.
112 if (til::ThreadSafetyTIL::isTrivial(V->definition())) {
113 E = V->definition();
114 continue;
115 }
116 return V;
117 }
118 if (auto *Ph = dyn_cast<Phi>(E)) {
119 if (Ph->status() == Phi::PH_Incomplete)
120 simplifyIncompleteArg(Ph);
121 // Eliminate redundant Phi nodes.
122 if (Ph->status() == Phi::PH_SingleVal) {
123 E = Ph->values()[0];
124 continue;
125 }
126 }
127 return E;
128 }
129 }
130
131 // Trace the arguments of an incomplete Phi node to see if they have the same
132 // canonical definition. If so, mark the Phi node as redundant.
133 // getCanonicalVal() will recursively call simplifyIncompletePhi().
simplifyIncompleteArg(til::Phi * Ph)134 void til::simplifyIncompleteArg(til::Phi *Ph) {
135 assert(Ph && Ph->status() == Phi::PH_Incomplete);
136
137 // eliminate infinite recursion -- assume that this node is not redundant.
138 Ph->setStatus(Phi::PH_MultiVal);
139
140 SExpr *E0 = simplifyToCanonicalVal(Ph->values()[0]);
141 for (unsigned i = 1, n = Ph->values().size(); i < n; ++i) {
142 SExpr *Ei = simplifyToCanonicalVal(Ph->values()[i]);
143 if (Ei == Ph)
144 continue; // Recursive reference to itself. Don't count.
145 if (Ei != E0) {
146 return; // Status is already set to MultiVal.
147 }
148 }
149 Ph->setStatus(Phi::PH_SingleVal);
150 }
151
152 // Renumbers the arguments and instructions to have unique, sequential IDs.
renumberInstrs(int ID)153 int BasicBlock::renumberInstrs(int ID) {
154 for (auto *Arg : Args)
155 Arg->setID(this, ID++);
156 for (auto *Instr : Instrs)
157 Instr->setID(this, ID++);
158 TermInstr->setID(this, ID++);
159 return ID;
160 }
161
162 // Sorts the CFGs blocks using a reverse post-order depth-first traversal.
163 // Each block will be written into the Blocks array in order, and its BlockID
164 // will be set to the index in the array. Sorting should start from the entry
165 // block, and ID should be the total number of blocks.
topologicalSort(SimpleArray<BasicBlock * > & Blocks,int ID)166 int BasicBlock::topologicalSort(SimpleArray<BasicBlock *> &Blocks, int ID) {
167 if (Visited) return ID;
168 Visited = true;
169 for (auto *Block : successors())
170 ID = Block->topologicalSort(Blocks, ID);
171 // set ID and update block array in place.
172 // We may lose pointers to unreachable blocks.
173 assert(ID > 0);
174 BlockID = --ID;
175 Blocks[BlockID] = this;
176 return ID;
177 }
178
179 // Performs a reverse topological traversal, starting from the exit block and
180 // following back-edges. The dominator is serialized before any predecessors,
181 // which guarantees that all blocks are serialized after their dominator and
182 // before their post-dominator (because it's a reverse topological traversal).
183 // ID should be initially set to 0.
184 //
185 // This sort assumes that (1) dominators have been computed, (2) there are no
186 // critical edges, and (3) the entry block is reachable from the exit block
187 // and no blocks are accessible via traversal of back-edges from the exit that
188 // weren't accessible via forward edges from the entry.
topologicalFinalSort(SimpleArray<BasicBlock * > & Blocks,int ID)189 int BasicBlock::topologicalFinalSort(SimpleArray<BasicBlock*>& Blocks, int ID) {
190 // Visited is assumed to have been set by the topologicalSort. This pass
191 // assumes !Visited means that we've visited this node before.
192 if (!Visited) return ID;
193 Visited = false;
194 if (DominatorNode.Parent)
195 ID = DominatorNode.Parent->topologicalFinalSort(Blocks, ID);
196 for (auto *Pred : Predecessors)
197 ID = Pred->topologicalFinalSort(Blocks, ID);
198 assert(static_cast<size_t>(ID) < Blocks.size());
199 BlockID = ID++;
200 Blocks[BlockID] = this;
201 return ID;
202 }
203
204 // Computes the immediate dominator of the current block. Assumes that all of
205 // its predecessors have already computed their dominators. This is achieved
206 // by visiting the nodes in topological order.
computeDominator()207 void BasicBlock::computeDominator() {
208 BasicBlock *Candidate = nullptr;
209 // Walk backwards from each predecessor to find the common dominator node.
210 for (auto *Pred : Predecessors) {
211 // Skip back-edges
212 if (Pred->BlockID >= BlockID) continue;
213 // If we don't yet have a candidate for dominator yet, take this one.
214 if (Candidate == nullptr) {
215 Candidate = Pred;
216 continue;
217 }
218 // Walk the alternate and current candidate back to find a common ancestor.
219 auto *Alternate = Pred;
220 while (Alternate != Candidate) {
221 if (Candidate->BlockID > Alternate->BlockID)
222 Candidate = Candidate->DominatorNode.Parent;
223 else
224 Alternate = Alternate->DominatorNode.Parent;
225 }
226 }
227 DominatorNode.Parent = Candidate;
228 DominatorNode.SizeOfSubTree = 1;
229 }
230
231 // Computes the immediate post-dominator of the current block. Assumes that all
232 // of its successors have already computed their post-dominators. This is
233 // achieved visiting the nodes in reverse topological order.
computePostDominator()234 void BasicBlock::computePostDominator() {
235 BasicBlock *Candidate = nullptr;
236 // Walk back from each predecessor to find the common post-dominator node.
237 for (auto *Succ : successors()) {
238 // Skip back-edges
239 if (Succ->BlockID <= BlockID) continue;
240 // If we don't yet have a candidate for post-dominator yet, take this one.
241 if (Candidate == nullptr) {
242 Candidate = Succ;
243 continue;
244 }
245 // Walk the alternate and current candidate back to find a common ancestor.
246 auto *Alternate = Succ;
247 while (Alternate != Candidate) {
248 if (Candidate->BlockID < Alternate->BlockID)
249 Candidate = Candidate->PostDominatorNode.Parent;
250 else
251 Alternate = Alternate->PostDominatorNode.Parent;
252 }
253 }
254 PostDominatorNode.Parent = Candidate;
255 PostDominatorNode.SizeOfSubTree = 1;
256 }
257
258 // Renumber instructions in all blocks
renumberInstrs()259 void SCFG::renumberInstrs() {
260 int InstrID = 0;
261 for (auto *Block : Blocks)
262 InstrID = Block->renumberInstrs(InstrID);
263 }
264
computeNodeSize(BasicBlock * B,BasicBlock::TopologyNode BasicBlock::* TN)265 static inline void computeNodeSize(BasicBlock *B,
266 BasicBlock::TopologyNode BasicBlock::*TN) {
267 BasicBlock::TopologyNode *N = &(B->*TN);
268 if (N->Parent) {
269 BasicBlock::TopologyNode *P = &(N->Parent->*TN);
270 // Initially set ID relative to the (as yet uncomputed) parent ID
271 N->NodeID = P->SizeOfSubTree;
272 P->SizeOfSubTree += N->SizeOfSubTree;
273 }
274 }
275
computeNodeID(BasicBlock * B,BasicBlock::TopologyNode BasicBlock::* TN)276 static inline void computeNodeID(BasicBlock *B,
277 BasicBlock::TopologyNode BasicBlock::*TN) {
278 BasicBlock::TopologyNode *N = &(B->*TN);
279 if (N->Parent) {
280 BasicBlock::TopologyNode *P = &(N->Parent->*TN);
281 N->NodeID += P->NodeID; // Fix NodeIDs relative to starting node.
282 }
283 }
284
285 // Normalizes a CFG. Normalization has a few major components:
286 // 1) Removing unreachable blocks.
287 // 2) Computing dominators and post-dominators
288 // 3) Topologically sorting the blocks into the "Blocks" array.
computeNormalForm()289 void SCFG::computeNormalForm() {
290 // Topologically sort the blocks starting from the entry block.
291 int NumUnreachableBlocks = Entry->topologicalSort(Blocks, Blocks.size());
292 if (NumUnreachableBlocks > 0) {
293 // If there were unreachable blocks shift everything down, and delete them.
294 for (size_t I = NumUnreachableBlocks, E = Blocks.size(); I < E; ++I) {
295 size_t NI = I - NumUnreachableBlocks;
296 Blocks[NI] = Blocks[I];
297 Blocks[NI]->BlockID = NI;
298 // FIXME: clean up predecessor pointers to unreachable blocks?
299 }
300 Blocks.drop(NumUnreachableBlocks);
301 }
302
303 // Compute dominators.
304 for (auto *Block : Blocks)
305 Block->computeDominator();
306
307 // Once dominators have been computed, the final sort may be performed.
308 int NumBlocks = Exit->topologicalFinalSort(Blocks, 0);
309 assert(static_cast<size_t>(NumBlocks) == Blocks.size());
310 (void) NumBlocks;
311
312 // Renumber the instructions now that we have a final sort.
313 renumberInstrs();
314
315 // Compute post-dominators and compute the sizes of each node in the
316 // dominator tree.
317 for (auto *Block : Blocks.reverse()) {
318 Block->computePostDominator();
319 computeNodeSize(Block, &BasicBlock::DominatorNode);
320 }
321 // Compute the sizes of each node in the post-dominator tree and assign IDs in
322 // the dominator tree.
323 for (auto *Block : Blocks) {
324 computeNodeID(Block, &BasicBlock::DominatorNode);
325 computeNodeSize(Block, &BasicBlock::PostDominatorNode);
326 }
327 // Assign IDs in the post-dominator tree.
328 for (auto *Block : Blocks.reverse()) {
329 computeNodeID(Block, &BasicBlock::PostDominatorNode);
330 }
331 }
332