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 static cl::String InputFilename("", "Specify input bytecode file", 0, "-");
22 static cl::String ExtractFunc("func", "Specify function to extract", 0, "main");
24 struct FunctionExtractorPass : public Pass {
25 const char *getPassName() const { return "Function Extractor"; }
28 // Mark all global variables to be internal
29 for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I)
30 I->setInternalLinkage(true);
34 // Loop over all of the functions in the module, dropping all references in
35 // functions that are not the named function.
36 for (Module::iterator I = M.begin(), E = M.end(); I != E;)
37 // Check to see if this is the named function!
38 if (!Named && I->getName() == ExtractFunc) {
39 // Yes, it is. Keep track of it...
42 // Make sure it's globally accessable...
43 Named->setInternalLinkage(false);
45 // Remove the named function from the module.
46 M.getFunctionList().remove(I);
48 // Nope it's not the named function, delete the body of the function
49 I->dropAllReferences();
53 // All of the functions that still have uses now must be used by global
54 // variables or the named function. Loop through them and create a new,
55 // external function for the used ones... making all uses point to the new
57 std::vector<Function*> NewFunctions;
59 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
60 if (!I->use_empty()) {
61 Function *New = new Function(I->getFunctionType(), false, I->getName());
62 I->replaceAllUsesWith(New);
63 NewFunctions.push_back(New);
66 // Now the module only has unused functions with their references dropped.
67 // Delete them all now!
68 M.getFunctionList().clear();
70 // Re-insert the named function...
72 M.getFunctionList().push_back(Named);
74 std::cerr << "Warning: Function '" << ExtractFunc << "' not found!\n";
76 // Insert all of the function stubs...
77 M.getFunctionList().insert(M.end(), NewFunctions.begin(),
84 int main(int argc, char **argv) {
85 cl::ParseCommandLineOptions(argc, argv, " llvm extractor\n");
87 std::auto_ptr<Module> M(ParseBytecodeFile(InputFilename));
89 std::cerr << "bytecode didn't read correctly.\n";
93 // In addition to just parsing the input from GCC, we also want to spiff it up
94 // a little bit. Do this now.
97 Passes.add(new FunctionExtractorPass());
98 Passes.add(createGlobalDCEPass()); // Delete unreachable globals
99 Passes.add(createConstantMergePass()); // Merge dup global constants
100 Passes.add(createCleanupGCCOutputPass()); // Fix gccisms
101 Passes.add(new WriteBytecodePass(&std::cout)); // Write bytecode to file...
103 Passes.run(*M.get());