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* Extract makes all global vars external, so they don't have initializers git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@4121 91177308-0d34-0410-b5e6-96231b3b80d8
140 lines
4.7 KiB
C++
140 lines
4.7 KiB
C++
//===----------------------------------------------------------------------===//
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// LLVM extract Utility
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//
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// This utility changes the input module to only contain a single function,
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// which is primarily used for debugging transformations.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Module.h"
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#include "llvm/PassManager.h"
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#include "llvm/Bytecode/Reader.h"
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#include "llvm/Bytecode/WriteBytecodePass.h"
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#include "llvm/Transforms/IPO.h"
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#include "Support/CommandLine.h"
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#include <memory>
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// InputFilename - The filename to read from.
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static cl::opt<std::string>
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InputFilename(cl::Positional, cl::desc("<input bytecode file>"),
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cl::init("-"), cl::value_desc("filename"));
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// ExtractFunc - The function to extract from the module... defaults to main.
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static cl::opt<std::string>
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ExtractFunc("func", cl::desc("Specify function to extract"), cl::init("main"),
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cl::value_desc("function"));
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struct FunctionExtractorPass : public Pass {
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bool run(Module &M) {
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// Mark all global variables to be internal
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for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I)
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if (!I->isExternal()) {
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I->setInitializer(0); // Make all variables external
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I->setInternalLinkage(false); // Make sure it's not internal
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}
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Function *Named = 0;
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// Loop over all of the functions in the module, dropping all references in
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// functions that are not the named function.
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for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
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// Check to see if this is the named function!
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if (I->getName() == ExtractFunc && !I->isExternal()) {
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if (Named) { // Two functions, same name?
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std::cerr << "extract ERROR: Two functions named: '" << ExtractFunc
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<< "' found!\n";
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exit(1);
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}
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// Yes, it is. Keep track of it...
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Named = I;
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// Make sure it's globally accessable...
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Named->setInternalLinkage(false);
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}
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if (Named == 0) {
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std::cerr << "Warning: Function '" << ExtractFunc << "' not found!\n";
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return false;
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}
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// All of the functions may be used by global variables or the named
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// function. Loop through them and create a new, external functions that
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// can be "used", instead of ones with bodies.
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//
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std::vector<Function*> NewFunctions;
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Function *Last = &M.back(); // Figure out where the last real fn is...
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for (Module::iterator I = M.begin(); ; ++I) {
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if (I->getName() != ExtractFunc) {
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Function *New = new Function(I->getFunctionType(), false, I->getName());
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I->setName(""); // Remove Old name
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// If it's not the named function, delete the body of the function
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I->dropAllReferences();
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M.getFunctionList().push_back(New);
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NewFunctions.push_back(New);
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}
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if (&*I == Last) break; // Stop after processing the last function
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}
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// Now that we have replacements all set up, loop through the module,
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// deleting the old functions, replacing them with the newly created
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// functions.
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if (!NewFunctions.empty()) {
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unsigned FuncNum = 0;
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Module::iterator I = M.begin();
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do {
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if (I->getName() != ExtractFunc) {
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// Make everything that uses the old function use the new dummy fn
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I->replaceAllUsesWith(NewFunctions[FuncNum++]);
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Function *Old = I;
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++I; // Move the iterator to the new function
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// Delete the old function!
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M.getFunctionList().erase(Old);
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} else {
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++I; // Skip the function we are extracting
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}
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} while (&*I != NewFunctions[0]);
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}
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return true;
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}
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};
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static RegisterPass<FunctionExtractorPass> X("extract", "Function Extractor");
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int main(int argc, char **argv) {
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cl::ParseCommandLineOptions(argc, argv, " llvm extractor\n");
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std::auto_ptr<Module> M(ParseBytecodeFile(InputFilename));
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if (M.get() == 0) {
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std::cerr << argv[0] << ": bytecode didn't read correctly.\n";
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return 1;
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}
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// In addition to just parsing the input from GCC, we also want to spiff it up
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// a little bit. Do this now.
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//
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PassManager Passes;
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Passes.add(new FunctionExtractorPass());
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Passes.add(createGlobalDCEPass()); // Delete unreachable globals
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Passes.add(createFunctionResolvingPass()); // Delete prototypes
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Passes.add(createConstantMergePass()); // Merge dup global constants
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Passes.add(createDeadTypeEliminationPass()); // Remove dead types...
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Passes.add(new WriteBytecodePass(&std::cout)); // Write bytecode to file...
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Passes.run(*M.get());
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return 0;
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}
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