7//===----------------------------------------------------------------------===//
8///
9/// \file
10/// \brief This file implements WebAssemblyException information analysis.
11///
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_LIB_TARGET_WEBASSEMBLY_WEBASSEMBLYEXCEPTIONINFO_H
15#define LLVM_LIB_TARGET_WEBASSEMBLY_WEBASSEMBLYEXCEPTIONINFO_H
16
17#include "WebAssembly.h"
18#include "llvm/ADT/SetVector.h"
19#include "llvm/CodeGen/MachineFunctionPass.h"
20
21namespace llvm {
22
23class MachineDominatorTree;
24class MachineDominanceFrontier;
25
26// WebAssembly instructions for exception handling are structured as follows:
27// try
28// instructions*
29// catch ----|
30// instructions* | -> A WebAssemblyException consists of this region
31// end ----|
32//
33// A WebAssemblyException object contains BBs that belong to a 'catch' part of
34// the try-catch-end structure to be created later. 'try' and 'end' markers
35// are not present at this stage and will be generated in CFGStackify pass.
36// Because CFGSort requires all the BBs within a catch part to be sorted
37// together as it does for loops, this pass calculates the nesting structure of
38// catch part of exceptions in a function.
39//
40// An exception catch part is defined as a BB with catch instruction and all
41// other BBs dominated by this BB.
42class WebAssemblyException {
43 MachineBasicBlock *EHPad = nullptr;
44
45 WebAssemblyException *ParentException = nullptr;
46 std::vector<WebAssemblyException *> SubExceptions;
47 std::vector<MachineBasicBlock *> Blocks;
48 SmallPtrSet<const MachineBasicBlock *, 8> BlockSet;
49
50public:
51 WebAssemblyException(MachineBasicBlock *EHPad) : EHPad(EHPad) {}
52 ~WebAssemblyException() { DeleteContainerPointers(SubExceptions); }
53 WebAssemblyException(const WebAssemblyException &) = delete;
54 const WebAssemblyException &operator=(const WebAssemblyException &) = delete;
55
56 MachineBasicBlock *getEHPad() const { return EHPad; }
57 MachineBasicBlock *getHeader() const { return EHPad; }
58 WebAssemblyException *getParentException() const { return ParentException; }
59 void setParentException(WebAssemblyException *WE) { ParentException = WE; }
60
61 bool contains(const WebAssemblyException *WE) const {
62 if (WE == this)
63 return true;
64 if (!WE)
65 return false;
66 return contains(WE->getParentException());
67 }
68 bool contains(const MachineBasicBlock *MBB) const {
69 return BlockSet.count(MBB);
70 }
71
72 void addBlock(MachineBasicBlock *MBB) {
73 Blocks.push_back(MBB);
74 BlockSet.insert(MBB);
75 }
76 ArrayRef<MachineBasicBlock *> getBlocks() const { return Blocks; }
77 using block_iterator = typename ArrayRef<MachineBasicBlock *>::const_iterator;
78 block_iterator block_begin() const { return getBlocks().begin(); }
79 block_iterator block_end() const { return getBlocks().end(); }
80 inline iterator_range<block_iterator> blocks() const {
81 return make_range(block_begin(), block_end());
82 }
83 unsigned getNumBlocks() const { return Blocks.size(); }
84 std::vector<MachineBasicBlock *> &getBlocksVector() { return Blocks; }
85
86 const std::vector<WebAssemblyException *> &getSubExceptions() const {
87 return SubExceptions;
88 }
89 std::vector<WebAssemblyException *> &getSubExceptions() {
90 return SubExceptions;
91 }
92 void addSubException(WebAssemblyException *E) { SubExceptions.push_back(E); }
93 using iterator = typename std::vector<WebAssemblyException *>::const_iterator;
94 iterator begin() const { return SubExceptions.begin(); }
95 iterator end() const { return SubExceptions.end(); }
96
97 void reserveBlocks(unsigned Size) { Blocks.reserve(Size); }
98 void reverseBlock(unsigned From = 0) {
99 std::reverse(Blocks.begin() + From, Blocks.end());
100 }
101
102 // Return the nesting level. An outermost one has depth 1.
103 unsigned getExceptionDepth() const {
104 unsigned D = 1;
105 for (const WebAssemblyException *CurException = ParentException;
106 CurException; CurException = CurException->ParentException)
107 ++D;
108 return D;
109 }
110
111 void print(raw_ostream &OS, unsigned Depth = 0) const;
112 void dump() const;
113};
114
115raw_ostream &operator<<(raw_ostream &OS, const WebAssemblyException &WE);
116
117class WebAssemblyExceptionInfo final : public MachineFunctionPass {
118 // Mapping of basic blocks to the innermost exception they occur in
119 DenseMap<const MachineBasicBlock *, WebAssemblyException *> BBMap;
120 std::vector<WebAssemblyException *> TopLevelExceptions;
121
122 void discoverAndMapException(WebAssemblyException *WE,
123 const MachineDominatorTree &MDT,
124 const MachineDominanceFrontier &MDF);
125 WebAssemblyException *getOutermostException(MachineBasicBlock *MBB) const;
126
127public:
128 static char ID;
129 WebAssemblyExceptionInfo() : MachineFunctionPass(ID) {
130 initializeWebAssemblyExceptionInfoPass(*PassRegistry::getPassRegistry());
131 }
132 ~WebAssemblyExceptionInfo() override { releaseMemory(); }
133 WebAssemblyExceptionInfo(const WebAssemblyExceptionInfo &) = delete;
134 WebAssemblyExceptionInfo &
135 operator=(const WebAssemblyExceptionInfo &) = delete;
136
137 bool runOnMachineFunction(MachineFunction &) override;
138 void releaseMemory() override;
139 void recalculate(MachineDominatorTree &MDT,
140 const MachineDominanceFrontier &MDF);
141 void getAnalysisUsage(AnalysisUsage &AU) const override;
142
143 bool empty() const { return TopLevelExceptions.empty(); }
144
145 // Return the innermost exception that MBB lives in. If the block is not in an
146 // exception, null is returned.
147 WebAssemblyException *getExceptionFor(const MachineBasicBlock *MBB) const {
148 return BBMap.lookup(MBB);
149 }
150
151 void changeExceptionFor(MachineBasicBlock *MBB, WebAssemblyException *WE) {
152 if (!WE) {
153 BBMap.erase(MBB);
154 return;
155 }
156 BBMap[MBB] = WE;
157 }
158
159 void addTopLevelException(WebAssemblyException *WE) {
160 assert(!WE->getParentException() && "Not a top level exception!");
161 TopLevelExceptions.push_back(WE);
162 }
163
164 void print(raw_ostream &OS, const Module *M = nullptr) const override;
165};
166
167} // end namespace llvm
168
169#endif
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