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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/GlobalVariable.h"
#include "llvm/Function.h"
#include "llvm/Transforms/IPO/GlobalDCE.h"
#include "llvm/Transforms/ConstantMerge.h"
#include "llvm/Transforms/CleanupGCCOutput.h"
#include "Support/CommandLine.h"
#include <memory>
// InputFilename - The filename to read from.
static cl::opt<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<string>
ExtractFunc("func", cl::desc("Specify function to extract"), cl::init("main"),
cl::value_desc("function"));
struct FunctionExtractorPass : public Pass {
const char *getPassName() const { return "Function Extractor"; }
bool run(Module &M) {
// Mark all global variables to be internal
for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I)
I->setInternalLinkage(true);
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;)
// Check to see if this is the named function!
if (!Named && I->getName() == ExtractFunc) {
// Yes, it is. Keep track of it...
Named = I;
// Make sure it's globally accessable...
Named->setInternalLinkage(false);
// Remove the named function from the module.
M.getFunctionList().remove(I);
} else {
// Nope it's not the named function, delete the body of the function
I->dropAllReferences();
++I;
}
// All of the functions that still have uses now must be used by global
// variables or the named function. Loop through them and create a new,
// external function for the used ones... making all uses point to the new
// functions.
std::vector<Function*> NewFunctions;
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
if (!I->use_empty()) {
Function *New = new Function(I->getFunctionType(), false, I->getName());
I->replaceAllUsesWith(New);
NewFunctions.push_back(New);
}
// Now the module only has unused functions with their references dropped.
// Delete them all now!
M.getFunctionList().clear();
// Re-insert the named function...
if (Named)
M.getFunctionList().push_back(Named);
else
std::cerr << "Warning: Function '" << ExtractFunc << "' not found!\n";
// Insert all of the function stubs...
M.getFunctionList().insert(M.end(), NewFunctions.begin(),
NewFunctions.end());
return true;
}
};
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 << "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(createConstantMergePass()); // Merge dup global constants
Passes.add(createCleanupGCCOutputPass()); // Fix gccisms
Passes.add(new WriteBytecodePass(&std::cout)); // Write bytecode to file...
Passes.run(*M.get());
return 0;
}
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