1 //===----------------------------------------------------------------------===//
2 // LLVM extract Utility
4 // This utility changes the input module to only contain a single function,
5 // which is primarily used for debugging transformations.
7 //===----------------------------------------------------------------------===//
9 #include "llvm/Module.h"
10 #include "llvm/PassManager.h"
11 #include "llvm/Bytecode/Reader.h"
12 #include "llvm/Bytecode/WriteBytecodePass.h"
13 #include "llvm/GlobalVariable.h"
14 #include "llvm/Function.h"
15 #include "llvm/Transforms/IPO/GlobalDCE.h"
16 #include "llvm/Transforms/IPO.h"
17 #include "Support/CommandLine.h"
20 // InputFilename - The filename to read from.
21 static cl::opt<string>
22 InputFilename(cl::Positional, cl::desc("<input bytecode file>"),
23 cl::init("-"), cl::value_desc("filename"));
26 // ExtractFunc - The function to extract from the module... defaults to main.
27 static cl::opt<string>
28 ExtractFunc("func", cl::desc("Specify function to extract"), cl::init("main"),
29 cl::value_desc("function"));
32 struct FunctionExtractorPass : public Pass {
34 // Mark all global variables to be internal
35 for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I)
36 I->setInternalLinkage(true);
40 // Loop over all of the functions in the module, dropping all references in
41 // functions that are not the named function.
42 for (Module::iterator I = M.begin(), E = M.end(); I != E;)
43 // Check to see if this is the named function!
44 if (!Named && I->getName() == ExtractFunc) {
45 // Yes, it is. Keep track of it...
48 // Make sure it's globally accessable...
49 Named->setInternalLinkage(false);
51 // Remove the named function from the module.
52 M.getFunctionList().remove(I);
54 // Nope it's not the named function, delete the body of the function
55 I->dropAllReferences();
59 // All of the functions that still have uses now must be used by global
60 // variables or the named function. Loop through them and create a new,
61 // external function for the used ones... making all uses point to the new
63 std::vector<Function*> NewFunctions;
65 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
66 if (!I->use_empty()) {
67 Function *New = new Function(I->getFunctionType(), false, I->getName());
68 I->replaceAllUsesWith(New);
69 NewFunctions.push_back(New);
72 // Now the module only has unused functions with their references dropped.
73 // Delete them all now!
74 M.getFunctionList().clear();
76 // Re-insert the named function...
78 M.getFunctionList().push_back(Named);
80 std::cerr << "Warning: Function '" << ExtractFunc << "' not found!\n";
82 // Insert all of the function stubs...
83 M.getFunctionList().insert(M.end(), NewFunctions.begin(),
90 static RegisterPass<FunctionExtractorPass> X("extract", "Function Extractor");
93 int main(int argc, char **argv) {
94 cl::ParseCommandLineOptions(argc, argv, " llvm extractor\n");
96 std::auto_ptr<Module> M(ParseBytecodeFile(InputFilename));
98 std::cerr << "bytecode didn't read correctly.\n";
102 // In addition to just parsing the input from GCC, we also want to spiff it up
103 // a little bit. Do this now.
106 Passes.add(new FunctionExtractorPass());
107 Passes.add(createGlobalDCEPass()); // Delete unreachable globals
108 Passes.add(createConstantMergePass()); // Merge dup global constants
109 Passes.add(createDeadTypeEliminationPass()); // Remove dead types...
110 Passes.add(new WriteBytecodePass(&std::cout)); // Write bytecode to file...
112 Passes.run(*M.get());