1 //===- GenericConvergenceVerifierImpl.h -----------------------*- C++ -*---===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 ///
9 /// \file
10 ///
11 /// A verifier for the static rules of convergence control tokens that works
12 /// with both LLVM IR and MIR.
13 ///
14 /// This template implementation resides in a separate file so that it does not
15 /// get injected into every .cpp file that includes the generic header.
16 ///
17 /// DO NOT INCLUDE THIS FILE WHEN MERELY USING CYCLEINFO.
18 ///
19 /// This file should only be included by files that implement a
20 /// specialization of the relevant templates. Currently these are:
21 /// - llvm/lib/IR/Verifier.cpp
22 /// - llvm/lib/CodeGen/MachineVerifier.cpp
23 ///
24 //===----------------------------------------------------------------------===//
25 
26 #ifndef LLVM_IR_GENERICCONVERGENCEVERIFIERIMPL_H
27 #define LLVM_IR_GENERICCONVERGENCEVERIFIERIMPL_H
28 
29 #include "llvm/ADT/GenericConvergenceVerifier.h"
30 #include "llvm/ADT/PostOrderIterator.h"
31 #include "llvm/ADT/Twine.h"
32 #include "llvm/IR/IntrinsicInst.h"
33 
34 #define Check(C, ...)                                                          \
35   do {                                                                         \
36     if (!(C)) {                                                                \
37       reportFailure(__VA_ARGS__);                                              \
38       return;                                                                  \
39     }                                                                          \
40   } while (false)
41 
42 #define CheckOrNull(C, ...)                                                    \
43   do {                                                                         \
44     if (!(C)) {                                                                \
45       reportFailure(__VA_ARGS__);                                              \
46       return {};                                                               \
47     }                                                                          \
48   } while (false)
49 
50 namespace llvm {
51 template <class ContextT> void GenericConvergenceVerifier<ContextT>::clear() {
52   Tokens.clear();
53   CI.clear();
54   ConvergenceKind = NoConvergence;
55 }
56 
57 template <class ContextT>
58 void GenericConvergenceVerifier<ContextT>::visit(const BlockT &BB) {
59   SeenFirstConvOp = false;
60 }
61 
62 template <class ContextT>
63 void GenericConvergenceVerifier<ContextT>::visit(const InstructionT &I) {
64   auto ID = ContextT::getIntrinsicID(I);
65   auto *TokenDef = findAndCheckConvergenceTokenUsed(I);
66   bool IsCtrlIntrinsic = true;
67 
68   switch (ID) {
69   case Intrinsic::experimental_convergence_entry:
70     Check(isInsideConvergentFunction(I),
71           "Entry intrinsic can occur only in a convergent function.",
72           {Context.print(&I)});
73     Check(I.getParent()->isEntryBlock(),
74           "Entry intrinsic can occur only in the entry block.",
75           {Context.print(&I)});
76     Check(!SeenFirstConvOp,
77           "Entry intrinsic cannot be preceded by a convergent operation in the "
78           "same basic block.",
79           {Context.print(&I)});
80     LLVM_FALLTHROUGH;
81   case Intrinsic::experimental_convergence_anchor:
82     Check(!TokenDef,
83           "Entry or anchor intrinsic cannot have a convergencectrl token "
84           "operand.",
85           {Context.print(&I)});
86     break;
87   case Intrinsic::experimental_convergence_loop:
88     Check(TokenDef, "Loop intrinsic must have a convergencectrl token operand.",
89           {Context.print(&I)});
90     Check(!SeenFirstConvOp,
91           "Loop intrinsic cannot be preceded by a convergent operation in the "
92           "same basic block.",
93           {Context.print(&I)});
94     break;
95   default:
96     IsCtrlIntrinsic = false;
97     break;
98   }
99 
100   if (isConvergent(I))
101     SeenFirstConvOp = true;
102 
103   if (TokenDef || IsCtrlIntrinsic) {
104     Check(isConvergent(I),
105           "Convergence control token can only be used in a convergent call.",
106           {Context.print(&I)});
107     Check(ConvergenceKind != UncontrolledConvergence,
108           "Cannot mix controlled and uncontrolled convergence in the same "
109           "function.",
110           {Context.print(&I)});
111     ConvergenceKind = ControlledConvergence;
112   } else if (isConvergent(I)) {
113     Check(ConvergenceKind != ControlledConvergence,
114           "Cannot mix controlled and uncontrolled convergence in the same "
115           "function.",
116           {Context.print(&I)});
117     ConvergenceKind = UncontrolledConvergence;
118   }
119 }
120 
121 template <class ContextT>
122 void GenericConvergenceVerifier<ContextT>::reportFailure(
123     const Twine &Message, ArrayRef<Printable> DumpedValues) {
124   FailureCB(Message);
125   if (OS) {
126     for (auto V : DumpedValues)
127       *OS << V << '\n';
128   }
129 }
130 
131 template <class ContextT>
132 void GenericConvergenceVerifier<ContextT>::verify(const DominatorTreeT &DT) {
133   assert(Context.getFunction());
134   const auto &F = *Context.getFunction();
135 
136   DenseMap<const BlockT *, SmallVector<const InstructionT *, 8>> LiveTokenMap;
137   DenseMap<const CycleT *, const InstructionT *> CycleHearts;
138 
139   // Just like the DominatorTree, compute the CycleInfo locally so that we
140   // can run the verifier outside of a pass manager and we don't rely on
141   // potentially out-dated analysis results.
142   CI.compute(const_cast<FunctionT &>(F));
143 
144   auto checkToken = [&](const InstructionT *Token, const InstructionT *User,
145                         SmallVectorImpl<const InstructionT *> &LiveTokens) {
146     Check(llvm::is_contained(LiveTokens, Token),
147           "Convergence region is not well-nested.",
148           {Context.print(Token), Context.print(User)});
149     while (LiveTokens.back() != Token)
150       LiveTokens.pop_back();
151 
152     // Check static rules about cycles.
153     auto *BB = User->getParent();
154     auto *BBCycle = CI.getCycle(BB);
155     if (!BBCycle)
156       return;
157 
158     auto *DefBB = Token->getParent();
159     if (DefBB == BB || BBCycle->contains(DefBB)) {
160       // degenerate occurrence of a loop intrinsic
161       return;
162     }
163 
164     Check(ContextT::getIntrinsicID(*User) ==
165               Intrinsic::experimental_convergence_loop,
166           "Convergence token used by an instruction other than "
167           "llvm.experimental.convergence.loop in a cycle that does "
168           "not contain the token's definition.",
169           {Context.print(User), CI.print(BBCycle)});
170 
171     while (true) {
172       auto *Parent = BBCycle->getParentCycle();
173       if (!Parent || Parent->contains(DefBB))
174         break;
175       BBCycle = Parent;
176     };
177 
178     Check(BBCycle->isReducible() && BB == BBCycle->getHeader(),
179           "Cycle heart must dominate all blocks in the cycle.",
180           {Context.print(User), Context.printAsOperand(BB), CI.print(BBCycle)});
181     Check(!CycleHearts.count(BBCycle),
182           "Two static convergence token uses in a cycle that does "
183           "not contain either token's definition.",
184           {Context.print(User), Context.print(CycleHearts[BBCycle]),
185            CI.print(BBCycle)});
186     CycleHearts[BBCycle] = User;
187   };
188 
189   ReversePostOrderTraversal<const FunctionT *> RPOT(&F);
190   SmallVector<const InstructionT *, 8> LiveTokens;
191   for (auto *BB : RPOT) {
192     LiveTokens.clear();
193     auto LTIt = LiveTokenMap.find(BB);
194     if (LTIt != LiveTokenMap.end()) {
195       LiveTokens = std::move(LTIt->second);
196       LiveTokenMap.erase(LTIt);
197     }
198 
199     for (auto &I : *BB) {
200       if (auto *Token = Tokens.lookup(&I))
201         checkToken(Token, &I, LiveTokens);
202       if (isConvergenceControlIntrinsic(ContextT::getIntrinsicID(I)))
203         LiveTokens.push_back(&I);
204     }
205 
206     // Propagate token liveness
207     for (auto *Succ : successors(BB)) {
208       auto *SuccNode = DT.getNode(Succ);
209       auto LTIt = LiveTokenMap.find(Succ);
210       if (LTIt == LiveTokenMap.end()) {
211         // We're the first predecessor: all tokens which dominate the
212         // successor are live for now.
213         LTIt = LiveTokenMap.try_emplace(Succ).first;
214         for (auto LiveToken : LiveTokens) {
215           if (!DT.dominates(DT.getNode(LiveToken->getParent()), SuccNode))
216             break;
217           LTIt->second.push_back(LiveToken);
218         }
219       } else {
220         // Compute the intersection of live tokens.
221         auto It = llvm::partition(
222             LTIt->second, [&LiveTokens](const InstructionT *Token) {
223               return llvm::is_contained(LiveTokens, Token);
224             });
225         LTIt->second.erase(It, LTIt->second.end());
226       }
227     }
228   }
229 }
230 
231 } // end namespace llvm
232 
233 #endif // LLVM_IR_GENERICCONVERGENCEVERIFIERIMPL_H
234