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/ConstantMerge.h"
17 #include "llvm/Transforms/CleanupGCCOutput.h"
18 #include "Support/CommandLine.h"
21 // InputFilename - The filename to read from.
22 static cl::opt<string>
23 InputFilename(cl::Positional, cl::desc("<input bytecode file>"),
24 cl::init("-"), cl::value_desc("filename"));
27 // ExtractFunc - The function to extract from the module... defaults to main.
28 static cl::opt<string>
29 ExtractFunc("func", cl::desc("Specify function to extract"), cl::init("main"),
30 cl::value_desc("function"));
33 struct FunctionExtractorPass : public Pass {
34 const char *getPassName() const { return "Function Extractor"; }
37 // Mark all global variables to be internal
38 for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I)
39 I->setInternalLinkage(true);
43 // Loop over all of the functions in the module, dropping all references in
44 // functions that are not the named function.
45 for (Module::iterator I = M.begin(), E = M.end(); I != E;)
46 // Check to see if this is the named function!
47 if (!Named && I->getName() == ExtractFunc) {
48 // Yes, it is. Keep track of it...
51 // Make sure it's globally accessable...
52 Named->setInternalLinkage(false);
54 // Remove the named function from the module.
55 M.getFunctionList().remove(I);
57 // Nope it's not the named function, delete the body of the function
58 I->dropAllReferences();
62 // All of the functions that still have uses now must be used by global
63 // variables or the named function. Loop through them and create a new,
64 // external function for the used ones... making all uses point to the new
66 std::vector<Function*> NewFunctions;
68 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
69 if (!I->use_empty()) {
70 Function *New = new Function(I->getFunctionType(), false, I->getName());
71 I->replaceAllUsesWith(New);
72 NewFunctions.push_back(New);
75 // Now the module only has unused functions with their references dropped.
76 // Delete them all now!
77 M.getFunctionList().clear();
79 // Re-insert the named function...
81 M.getFunctionList().push_back(Named);
83 std::cerr << "Warning: Function '" << ExtractFunc << "' not found!\n";
85 // Insert all of the function stubs...
86 M.getFunctionList().insert(M.end(), NewFunctions.begin(),
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(createCleanupGCCOutputPass()); // Fix gccisms
110 Passes.add(new WriteBytecodePass(&std::cout)); // Write bytecode to file...
112 Passes.run(*M.get());