1//===- BlockExtractor.cpp - Extracts blocks into their own functions ------===//
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// This pass extracts the specified basic blocks from the module into their
10// own functions.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/Transforms/IPO/BlockExtractor.h"
15#include "llvm/ADT/STLExtras.h"
16#include "llvm/ADT/Statistic.h"
17#include "llvm/IR/Instructions.h"
18#include "llvm/IR/Module.h"
19#include "llvm/IR/PassManager.h"
20#include "llvm/Support/CommandLine.h"
21#include "llvm/Support/Debug.h"
22#include "llvm/Support/MemoryBuffer.h"
23#include "llvm/Transforms/IPO.h"
24#include "llvm/Transforms/Utils/BasicBlockUtils.h"
25#include "llvm/Transforms/Utils/CodeExtractor.h"
26
27using namespace llvm;
28
29#define DEBUG_TYPE "block-extractor"
30
31STATISTIC(NumExtracted, "Number of basic blocks extracted");
32
33static cl::opt<std::string> BlockExtractorFile(
34 "extract-blocks-file", cl::value_desc("filename"),
35 cl::desc("A file containing list of basic blocks to extract"), cl::Hidden);
36
37static cl::opt<bool>
38 BlockExtractorEraseFuncs("extract-blocks-erase-funcs",
39 cl::desc("Erase the existing functions"),
40 cl::Hidden);
41namespace {
42class BlockExtractor {
43public:
44 BlockExtractor(bool EraseFunctions) : EraseFunctions(EraseFunctions) {}
45 bool runOnModule(Module &M);
46 void
47 init(const std::vector<std::vector<BasicBlock *>> &GroupsOfBlocksToExtract) {
48 GroupsOfBlocks = GroupsOfBlocksToExtract;
49 if (!BlockExtractorFile.empty())
50 loadFile();
51 }
52
53private:
54 std::vector<std::vector<BasicBlock *>> GroupsOfBlocks;
55 bool EraseFunctions;
56 /// Map a function name to groups of blocks.
57 SmallVector<std::pair<std::string, SmallVector<std::string, 4>>, 4>
58 BlocksByName;
59
60 void loadFile();
61 void splitLandingPadPreds(Function &F);
62};
63
64} // end anonymous namespace
65
66/// Gets all of the blocks specified in the input file.
67void BlockExtractor::loadFile() {
68 auto ErrOrBuf = MemoryBuffer::getFile(Filename: BlockExtractorFile);
69 if (ErrOrBuf.getError())
70 report_fatal_error(reason: "BlockExtractor couldn't load the file.");
71 // Read the file.
72 auto &Buf = *ErrOrBuf;
73 SmallVector<StringRef, 16> Lines;
74 Buf->getBuffer().split(A&: Lines, Separator: '\n', /*MaxSplit=*/-1,
75 /*KeepEmpty=*/false);
76 for (const auto &Line : Lines) {
77 SmallVector<StringRef, 4> LineSplit;
78 Line.split(A&: LineSplit, Separator: ' ', /*MaxSplit=*/-1,
79 /*KeepEmpty=*/false);
80 if (LineSplit.empty())
81 continue;
82 if (LineSplit.size()!=2)
83 report_fatal_error(reason: "Invalid line format, expecting lines like: 'funcname bb1[;bb2..]'",
84 /*GenCrashDiag=*/gen_crash_diag: false);
85 SmallVector<StringRef, 4> BBNames;
86 LineSplit[1].split(A&: BBNames, Separator: ';', /*MaxSplit=*/-1,
87 /*KeepEmpty=*/false);
88 if (BBNames.empty())
89 report_fatal_error(reason: "Missing bbs name");
90 BlocksByName.push_back(
91 Elt: {std::string(LineSplit[0]), {BBNames.begin(), BBNames.end()}});
92 }
93}
94
95/// Extracts the landing pads to make sure all of them have only one
96/// predecessor.
97void BlockExtractor::splitLandingPadPreds(Function &F) {
98 for (BasicBlock &BB : F) {
99 for (Instruction &I : BB) {
100 if (!isa<InvokeInst>(Val: &I))
101 continue;
102 InvokeInst *II = cast<InvokeInst>(Val: &I);
103 BasicBlock *Parent = II->getParent();
104 BasicBlock *LPad = II->getUnwindDest();
105
106 // Look through the landing pad's predecessors. If one of them ends in an
107 // 'invoke', then we want to split the landing pad.
108 bool Split = false;
109 for (auto *PredBB : predecessors(BB: LPad)) {
110 if (PredBB->isLandingPad() && PredBB != Parent &&
111 isa<InvokeInst>(Val: Parent->getTerminator())) {
112 Split = true;
113 break;
114 }
115 }
116
117 if (!Split)
118 continue;
119
120 SmallVector<BasicBlock *, 2> NewBBs;
121 SplitLandingPadPredecessors(OrigBB: LPad, Preds: Parent, Suffix: ".1", Suffix2: ".2", NewBBs);
122 }
123 }
124}
125
126bool BlockExtractor::runOnModule(Module &M) {
127 bool Changed = false;
128
129 // Get all the functions.
130 SmallVector<Function *, 4> Functions;
131 for (Function &F : M) {
132 splitLandingPadPreds(F);
133 Functions.push_back(Elt: &F);
134 }
135
136 // Get all the blocks specified in the input file.
137 unsigned NextGroupIdx = GroupsOfBlocks.size();
138 GroupsOfBlocks.resize(new_size: NextGroupIdx + BlocksByName.size());
139 for (const auto &BInfo : BlocksByName) {
140 Function *F = M.getFunction(Name: BInfo.first);
141 if (!F)
142 report_fatal_error(reason: "Invalid function name specified in the input file",
143 /*GenCrashDiag=*/gen_crash_diag: false);
144 for (const auto &BBInfo : BInfo.second) {
145 auto Res = llvm::find_if(
146 Range&: *F, P: [&](const BasicBlock &BB) { return BB.getName() == BBInfo; });
147 if (Res == F->end())
148 report_fatal_error(reason: "Invalid block name specified in the input file",
149 /*GenCrashDiag=*/gen_crash_diag: false);
150 GroupsOfBlocks[NextGroupIdx].push_back(x: &*Res);
151 }
152 ++NextGroupIdx;
153 }
154
155 // Extract each group of basic blocks.
156 for (auto &BBs : GroupsOfBlocks) {
157 SmallVector<BasicBlock *, 32> BlocksToExtractVec;
158 for (BasicBlock *BB : BBs) {
159 // Check if the module contains BB.
160 if (BB->getParent()->getParent() != &M)
161 report_fatal_error(reason: "Invalid basic block", /*GenCrashDiag=*/gen_crash_diag: false);
162 LLVM_DEBUG(dbgs() << "BlockExtractor: Extracting "
163 << BB->getParent()->getName() << ":" << BB->getName()
164 << "\n");
165 BlocksToExtractVec.push_back(Elt: BB);
166 if (const InvokeInst *II = dyn_cast<InvokeInst>(Val: BB->getTerminator()))
167 BlocksToExtractVec.push_back(Elt: II->getUnwindDest());
168 ++NumExtracted;
169 Changed = true;
170 }
171 CodeExtractorAnalysisCache CEAC(*BBs[0]->getParent());
172 Function *F = CodeExtractor(BlocksToExtractVec).extractCodeRegion(CEAC);
173 if (F)
174 LLVM_DEBUG(dbgs() << "Extracted group '" << (*BBs.begin())->getName()
175 << "' in: " << F->getName() << '\n');
176 else
177 LLVM_DEBUG(dbgs() << "Failed to extract for group '"
178 << (*BBs.begin())->getName() << "'\n");
179 }
180
181 // Erase the functions.
182 if (EraseFunctions || BlockExtractorEraseFuncs) {
183 for (Function *F : Functions) {
184 LLVM_DEBUG(dbgs() << "BlockExtractor: Trying to delete " << F->getName()
185 << "\n");
186 F->deleteBody();
187 }
188 // Set linkage as ExternalLinkage to avoid erasing unreachable functions.
189 for (Function &F : M)
190 F.setLinkage(GlobalValue::ExternalLinkage);
191 Changed = true;
192 }
193
194 return Changed;
195}
196
197BlockExtractorPass::BlockExtractorPass(
198 std::vector<std::vector<BasicBlock *>> &&GroupsOfBlocks,
199 bool EraseFunctions)
200 : GroupsOfBlocks(GroupsOfBlocks), EraseFunctions(EraseFunctions) {}
201
202PreservedAnalyses BlockExtractorPass::run(Module &M,
203 ModuleAnalysisManager &AM) {
204 BlockExtractor BE(EraseFunctions);
205 BE.init(GroupsOfBlocksToExtract: GroupsOfBlocks);
206 return BE.runOnModule(M) ? PreservedAnalyses::none()
207 : PreservedAnalyses::all();
208}
209