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//===----------------------------------------------------------------------===//
// LLVM extract Utility
//
// This utility changes the input module to only contain a single function,
// which is primarily used for debugging transformations.
//
//===----------------------------------------------------------------------===//
#include "llvm/Module.h"
#include "llvm/PassManager.h"
#include "llvm/Bytecode/Reader.h"
#include "llvm/Bytecode/WriteBytecodePass.h"
#include "llvm/Transforms/IPO.h"
#include "Support/CommandLine.h"
#include <memory>
// InputFilename - The filename to read from.
static cl::opt<std::string>
InputFilename(cl::Positional, cl::desc("<input bytecode file>"),
cl::init("-"), cl::value_desc("filename"));
// ExtractFunc - The function to extract from the module... defaults to main.
static cl::opt<std::string>
ExtractFunc("func", cl::desc("Specify function to extract"), cl::init("main"),
cl::value_desc("function"));
struct FunctionExtractorPass : public Pass {
bool run(Module &M) {
// Mark all global variables to be internal
for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I)
if (!I->isExternal()) {
I->setInitializer(0); // Make all variables external
I->setInternalLinkage(false); // Make sure it's not internal
}
Function *Named = 0;
// Loop over all of the functions in the module, dropping all references in
// functions that are not the named function.
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
// Check to see if this is the named function!
if (I->getName() == ExtractFunc && !I->isExternal()) {
if (Named) { // Two functions, same name?
std::cerr << "extract ERROR: Two functions named: '" << ExtractFunc
<< "' found!\n";
exit(1);
}
// Yes, it is. Keep track of it...
Named = I;
// Make sure it's globally accessable...
Named->setInternalLinkage(false);
}
if (Named == 0) {
std::cerr << "Warning: Function '" << ExtractFunc << "' not found!\n";
return false;
}
// All of the functions may be used by global variables or the named
// function. Loop through them and create a new, external functions that
// can be "used", instead of ones with bodies.
//
std::vector<Function*> NewFunctions;
Function *Last = &M.back(); // Figure out where the last real fn is...
for (Module::iterator I = M.begin(); ; ++I) {
if (I->getName() != ExtractFunc) {
Function *New = new Function(I->getFunctionType(), false, I->getName());
I->setName(""); // Remove Old name
// If it's not the named function, delete the body of the function
I->dropAllReferences();
M.getFunctionList().push_back(New);
NewFunctions.push_back(New);
}
if (&*I == Last) break; // Stop after processing the last function
}
// Now that we have replacements all set up, loop through the module,
// deleting the old functions, replacing them with the newly created
// functions.
if (!NewFunctions.empty()) {
unsigned FuncNum = 0;
Module::iterator I = M.begin();
do {
if (I->getName() != ExtractFunc) {
// Make everything that uses the old function use the new dummy fn
I->replaceAllUsesWith(NewFunctions[FuncNum++]);
Function *Old = I;
++I; // Move the iterator to the new function
// Delete the old function!
M.getFunctionList().erase(Old);
} else {
++I; // Skip the function we are extracting
}
} while (&*I != NewFunctions[0]);
}
return true;
}
};
static RegisterPass<FunctionExtractorPass> X("extract", "Function Extractor");
int main(int argc, char **argv) {
cl::ParseCommandLineOptions(argc, argv, " llvm extractor\n");
std::auto_ptr<Module> M(ParseBytecodeFile(InputFilename));
if (M.get() == 0) {
std::cerr << argv[0] << ": bytecode didn't read correctly.\n";
return 1;
}
// In addition to just parsing the input from GCC, we also want to spiff it up
// a little bit. Do this now.
//
PassManager Passes;
Passes.add(new FunctionExtractorPass());
Passes.add(createGlobalDCEPass()); // Delete unreachable globals
Passes.add(createFunctionResolvingPass()); // Delete prototypes
Passes.add(createConstantMergePass()); // Merge dup global constants
Passes.add(createDeadTypeEliminationPass()); // Remove dead types...
Passes.add(new WriteBytecodePass(&std::cout)); // Write bytecode to file...
Passes.run(*M.get());
return 0;
}
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