1 //===- llvm-extract.cpp - LLVM function extraction utility ----------------===//
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 utility changes the input module to only contain a single function,
10 // which is primarily used for debugging transformations.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/ADT/SetVector.h"
15 #include "llvm/ADT/SmallPtrSet.h"
16 #include "llvm/Bitcode/BitcodeWriterPass.h"
17 #include "llvm/IR/DataLayout.h"
18 #include "llvm/IR/IRPrintingPasses.h"
19 #include "llvm/IR/Instructions.h"
20 #include "llvm/IR/LLVMContext.h"
21 #include "llvm/IR/Module.h"
22 #include "llvm/IRPrinter/IRPrintingPasses.h"
23 #include "llvm/IRReader/IRReader.h"
24 #include "llvm/Passes/PassBuilder.h"
25 #include "llvm/Support/CommandLine.h"
26 #include "llvm/Support/Error.h"
27 #include "llvm/Support/FileSystem.h"
28 #include "llvm/Support/InitLLVM.h"
29 #include "llvm/Support/Regex.h"
30 #include "llvm/Support/SourceMgr.h"
31 #include "llvm/Support/SystemUtils.h"
32 #include "llvm/Support/ToolOutputFile.h"
33 #include "llvm/Transforms/IPO.h"
34 #include "llvm/Transforms/IPO/BlockExtractor.h"
35 #include "llvm/Transforms/IPO/ExtractGV.h"
36 #include "llvm/Transforms/IPO/GlobalDCE.h"
37 #include "llvm/Transforms/IPO/StripDeadPrototypes.h"
38 #include "llvm/Transforms/IPO/StripSymbols.h"
39 #include <memory>
40 #include <utility>
41 
42 using namespace llvm;
43 
44 cl::OptionCategory ExtractCat("llvm-extract Options");
45 
46 // InputFilename - The filename to read from.
47 static cl::opt<std::string> InputFilename(cl::Positional,
48                                           cl::desc("<input bitcode file>"),
49                                           cl::init("-"),
50                                           cl::value_desc("filename"));
51 
52 static cl::opt<std::string> OutputFilename("o",
53                                            cl::desc("Specify output filename"),
54                                            cl::value_desc("filename"),
55                                            cl::init("-"), cl::cat(ExtractCat));
56 
57 static cl::opt<bool> Force("f", cl::desc("Enable binary output on terminals"),
58                            cl::cat(ExtractCat));
59 
60 static cl::opt<bool> DeleteFn("delete",
61                               cl::desc("Delete specified Globals from Module"),
62                               cl::cat(ExtractCat));
63 
64 static cl::opt<bool> KeepConstInit("keep-const-init",
65                               cl::desc("Keep initializers of constants"),
66                               cl::cat(ExtractCat));
67 
68 static cl::opt<bool>
69     Recursive("recursive", cl::desc("Recursively extract all called functions"),
70               cl::cat(ExtractCat));
71 
72 // ExtractFuncs - The functions to extract from the module.
73 static cl::list<std::string>
74     ExtractFuncs("func", cl::desc("Specify function to extract"),
75                  cl::value_desc("function"), cl::cat(ExtractCat));
76 
77 // ExtractRegExpFuncs - The functions, matched via regular expression, to
78 // extract from the module.
79 static cl::list<std::string>
80     ExtractRegExpFuncs("rfunc",
81                        cl::desc("Specify function(s) to extract using a "
82                                 "regular expression"),
83                        cl::value_desc("rfunction"), cl::cat(ExtractCat));
84 
85 // ExtractBlocks - The blocks to extract from the module.
86 static cl::list<std::string> ExtractBlocks(
87     "bb",
88     cl::desc(
89         "Specify <function, basic block1[;basic block2...]> pairs to extract.\n"
90         "Each pair will create a function.\n"
91         "If multiple basic blocks are specified in one pair,\n"
92         "the first block in the sequence should dominate the rest.\n"
93         "eg:\n"
94         "  --bb=f:bb1;bb2 will extract one function with both bb1 and bb2;\n"
95         "  --bb=f:bb1 --bb=f:bb2 will extract two functions, one with bb1, one "
96         "with bb2."),
97     cl::value_desc("function:bb1[;bb2...]"), cl::cat(ExtractCat));
98 
99 // ExtractAlias - The alias to extract from the module.
100 static cl::list<std::string>
101     ExtractAliases("alias", cl::desc("Specify alias to extract"),
102                    cl::value_desc("alias"), cl::cat(ExtractCat));
103 
104 // ExtractRegExpAliases - The aliases, matched via regular expression, to
105 // extract from the module.
106 static cl::list<std::string>
107     ExtractRegExpAliases("ralias",
108                          cl::desc("Specify alias(es) to extract using a "
109                                   "regular expression"),
110                          cl::value_desc("ralias"), cl::cat(ExtractCat));
111 
112 // ExtractGlobals - The globals to extract from the module.
113 static cl::list<std::string>
114     ExtractGlobals("glob", cl::desc("Specify global to extract"),
115                    cl::value_desc("global"), cl::cat(ExtractCat));
116 
117 // ExtractRegExpGlobals - The globals, matched via regular expression, to
118 // extract from the module...
119 static cl::list<std::string>
120     ExtractRegExpGlobals("rglob",
121                          cl::desc("Specify global(s) to extract using a "
122                                   "regular expression"),
123                          cl::value_desc("rglobal"), cl::cat(ExtractCat));
124 
125 static cl::opt<bool> OutputAssembly("S",
126                                     cl::desc("Write output as LLVM assembly"),
127                                     cl::Hidden, cl::cat(ExtractCat));
128 
129 static cl::opt<bool> PreserveBitcodeUseListOrder(
130     "preserve-bc-uselistorder",
131     cl::desc("Preserve use-list order when writing LLVM bitcode."),
132     cl::init(true), cl::Hidden, cl::cat(ExtractCat));
133 
134 static cl::opt<bool> PreserveAssemblyUseListOrder(
135     "preserve-ll-uselistorder",
136     cl::desc("Preserve use-list order when writing LLVM assembly."),
137     cl::init(false), cl::Hidden, cl::cat(ExtractCat));
138 
139 int main(int argc, char **argv) {
140   InitLLVM X(argc, argv);
141 
142   LLVMContext Context;
143   cl::HideUnrelatedOptions(ExtractCat);
144   cl::ParseCommandLineOptions(argc, argv, "llvm extractor\n");
145 
146   // Use lazy loading, since we only care about selected global values.
147   SMDiagnostic Err;
148   std::unique_ptr<Module> M = getLazyIRFileModule(InputFilename, Err, Context);
149 
150   if (!M.get()) {
151     Err.print(argv[0], errs());
152     return 1;
153   }
154 
155   // Use SetVector to avoid duplicates.
156   SetVector<GlobalValue *> GVs;
157 
158   // Figure out which aliases we should extract.
159   for (size_t i = 0, e = ExtractAliases.size(); i != e; ++i) {
160     GlobalAlias *GA = M->getNamedAlias(ExtractAliases[i]);
161     if (!GA) {
162       errs() << argv[0] << ": program doesn't contain alias named '"
163              << ExtractAliases[i] << "'!\n";
164       return 1;
165     }
166     GVs.insert(GA);
167   }
168 
169   // Extract aliases via regular expression matching.
170   for (size_t i = 0, e = ExtractRegExpAliases.size(); i != e; ++i) {
171     std::string Error;
172     Regex RegEx(ExtractRegExpAliases[i]);
173     if (!RegEx.isValid(Error)) {
174       errs() << argv[0] << ": '" << ExtractRegExpAliases[i] << "' "
175         "invalid regex: " << Error;
176     }
177     bool match = false;
178     for (Module::alias_iterator GA = M->alias_begin(), E = M->alias_end();
179          GA != E; GA++) {
180       if (RegEx.match(GA->getName())) {
181         GVs.insert(&*GA);
182         match = true;
183       }
184     }
185     if (!match) {
186       errs() << argv[0] << ": program doesn't contain global named '"
187              << ExtractRegExpAliases[i] << "'!\n";
188       return 1;
189     }
190   }
191 
192   // Figure out which globals we should extract.
193   for (size_t i = 0, e = ExtractGlobals.size(); i != e; ++i) {
194     GlobalValue *GV = M->getNamedGlobal(ExtractGlobals[i]);
195     if (!GV) {
196       errs() << argv[0] << ": program doesn't contain global named '"
197              << ExtractGlobals[i] << "'!\n";
198       return 1;
199     }
200     GVs.insert(GV);
201   }
202 
203   // Extract globals via regular expression matching.
204   for (size_t i = 0, e = ExtractRegExpGlobals.size(); i != e; ++i) {
205     std::string Error;
206     Regex RegEx(ExtractRegExpGlobals[i]);
207     if (!RegEx.isValid(Error)) {
208       errs() << argv[0] << ": '" << ExtractRegExpGlobals[i] << "' "
209         "invalid regex: " << Error;
210     }
211     bool match = false;
212     for (auto &GV : M->globals()) {
213       if (RegEx.match(GV.getName())) {
214         GVs.insert(&GV);
215         match = true;
216       }
217     }
218     if (!match) {
219       errs() << argv[0] << ": program doesn't contain global named '"
220              << ExtractRegExpGlobals[i] << "'!\n";
221       return 1;
222     }
223   }
224 
225   // Figure out which functions we should extract.
226   for (size_t i = 0, e = ExtractFuncs.size(); i != e; ++i) {
227     GlobalValue *GV = M->getFunction(ExtractFuncs[i]);
228     if (!GV) {
229       errs() << argv[0] << ": program doesn't contain function named '"
230              << ExtractFuncs[i] << "'!\n";
231       return 1;
232     }
233     GVs.insert(GV);
234   }
235   // Extract functions via regular expression matching.
236   for (size_t i = 0, e = ExtractRegExpFuncs.size(); i != e; ++i) {
237     std::string Error;
238     StringRef RegExStr = ExtractRegExpFuncs[i];
239     Regex RegEx(RegExStr);
240     if (!RegEx.isValid(Error)) {
241       errs() << argv[0] << ": '" << ExtractRegExpFuncs[i] << "' "
242         "invalid regex: " << Error;
243     }
244     bool match = false;
245     for (Module::iterator F = M->begin(), E = M->end(); F != E;
246          F++) {
247       if (RegEx.match(F->getName())) {
248         GVs.insert(&*F);
249         match = true;
250       }
251     }
252     if (!match) {
253       errs() << argv[0] << ": program doesn't contain global named '"
254              << ExtractRegExpFuncs[i] << "'!\n";
255       return 1;
256     }
257   }
258 
259   // Figure out which BasicBlocks we should extract.
260   SmallVector<std::pair<Function *, SmallVector<StringRef, 16>>, 2> BBMap;
261   for (StringRef StrPair : ExtractBlocks) {
262     SmallVector<StringRef, 16> BBNames;
263     auto BBInfo = StrPair.split(':');
264     // Get the function.
265     Function *F = M->getFunction(BBInfo.first);
266     if (!F) {
267       errs() << argv[0] << ": program doesn't contain a function named '"
268              << BBInfo.first << "'!\n";
269       return 1;
270     }
271     // Add the function to the materialize list, and store the basic block names
272     // to check after materialization.
273     GVs.insert(F);
274     BBInfo.second.split(BBNames, ';', /*MaxSplit=*/-1, /*KeepEmpty=*/false);
275     BBMap.push_back({F, std::move(BBNames)});
276   }
277 
278   // Use *argv instead of argv[0] to work around a wrong GCC warning.
279   ExitOnError ExitOnErr(std::string(*argv) + ": error reading input: ");
280 
281   if (Recursive) {
282     std::vector<llvm::Function *> Workqueue;
283     for (GlobalValue *GV : GVs) {
284       if (auto *F = dyn_cast<Function>(GV)) {
285         Workqueue.push_back(F);
286       }
287     }
288     while (!Workqueue.empty()) {
289       Function *F = &*Workqueue.back();
290       Workqueue.pop_back();
291       ExitOnErr(F->materialize());
292       for (auto &BB : *F) {
293         for (auto &I : BB) {
294           CallBase *CB = dyn_cast<CallBase>(&I);
295           if (!CB)
296             continue;
297           Function *CF = CB->getCalledFunction();
298           if (!CF)
299             continue;
300           if (CF->isDeclaration() || GVs.count(CF))
301             continue;
302           GVs.insert(CF);
303           Workqueue.push_back(CF);
304         }
305       }
306     }
307   }
308 
309   auto Materialize = [&](GlobalValue &GV) { ExitOnErr(GV.materialize()); };
310 
311   // Materialize requisite global values.
312   if (!DeleteFn) {
313     for (size_t i = 0, e = GVs.size(); i != e; ++i)
314       Materialize(*GVs[i]);
315   } else {
316     // Deleting. Materialize every GV that's *not* in GVs.
317     SmallPtrSet<GlobalValue *, 8> GVSet(GVs.begin(), GVs.end());
318     for (auto &F : *M) {
319       if (!GVSet.count(&F))
320         Materialize(F);
321     }
322   }
323 
324   {
325     std::vector<GlobalValue *> Gvs(GVs.begin(), GVs.end());
326     LoopAnalysisManager LAM;
327     FunctionAnalysisManager FAM;
328     CGSCCAnalysisManager CGAM;
329     ModuleAnalysisManager MAM;
330 
331     PassBuilder PB;
332 
333     PB.registerModuleAnalyses(MAM);
334     PB.registerCGSCCAnalyses(CGAM);
335     PB.registerFunctionAnalyses(FAM);
336     PB.registerLoopAnalyses(LAM);
337     PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
338 
339     ModulePassManager PM;
340     PM.addPass(ExtractGVPass(Gvs, DeleteFn, KeepConstInit));
341     PM.run(*M, MAM);
342 
343     // Now that we have all the GVs we want, mark the module as fully
344     // materialized.
345     // FIXME: should the GVExtractionPass handle this?
346     ExitOnErr(M->materializeAll());
347   }
348 
349   // Extract the specified basic blocks from the module and erase the existing
350   // functions.
351   if (!ExtractBlocks.empty()) {
352     // Figure out which BasicBlocks we should extract.
353     std::vector<std::vector<BasicBlock *>> GroupOfBBs;
354     for (auto &P : BBMap) {
355       std::vector<BasicBlock *> BBs;
356       for (StringRef BBName : P.second) {
357         // The function has been materialized, so add its matching basic blocks
358         // to the block extractor list, or fail if a name is not found.
359         auto Res = llvm::find_if(*P.first, [&](const BasicBlock &BB) {
360           return BB.getName().equals(BBName);
361         });
362         if (Res == P.first->end()) {
363           errs() << argv[0] << ": function " << P.first->getName()
364                  << " doesn't contain a basic block named '" << BBName
365                  << "'!\n";
366           return 1;
367         }
368         BBs.push_back(&*Res);
369       }
370       GroupOfBBs.push_back(BBs);
371     }
372 
373     LoopAnalysisManager LAM;
374     FunctionAnalysisManager FAM;
375     CGSCCAnalysisManager CGAM;
376     ModuleAnalysisManager MAM;
377 
378     PassBuilder PB;
379 
380     PB.registerModuleAnalyses(MAM);
381     PB.registerCGSCCAnalyses(CGAM);
382     PB.registerFunctionAnalyses(FAM);
383     PB.registerLoopAnalyses(LAM);
384     PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
385 
386     ModulePassManager PM;
387     PM.addPass(BlockExtractorPass(std::move(GroupOfBBs), true));
388     PM.run(*M, MAM);
389   }
390 
391   // In addition to deleting all other functions, we also want to spiff it
392   // up a little bit.  Do this now.
393 
394   LoopAnalysisManager LAM;
395   FunctionAnalysisManager FAM;
396   CGSCCAnalysisManager CGAM;
397   ModuleAnalysisManager MAM;
398 
399   PassBuilder PB;
400 
401   PB.registerModuleAnalyses(MAM);
402   PB.registerCGSCCAnalyses(CGAM);
403   PB.registerFunctionAnalyses(FAM);
404   PB.registerLoopAnalyses(LAM);
405   PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
406 
407   ModulePassManager PM;
408   if (!DeleteFn)
409     PM.addPass(GlobalDCEPass());
410   PM.addPass(StripDeadDebugInfoPass());
411   PM.addPass(StripDeadPrototypesPass());
412 
413   std::error_code EC;
414   ToolOutputFile Out(OutputFilename, EC, sys::fs::OF_None);
415   if (EC) {
416     errs() << EC.message() << '\n';
417     return 1;
418   }
419 
420   if (OutputAssembly)
421     PM.addPass(PrintModulePass(Out.os(), "", PreserveAssemblyUseListOrder));
422   else if (Force || !CheckBitcodeOutputToConsole(Out.os()))
423     PM.addPass(BitcodeWriterPass(Out.os(), PreserveBitcodeUseListOrder));
424 
425   PM.run(*M, MAM);
426 
427   // Declare success.
428   Out.keep();
429 
430   return 0;
431 }
432