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llvm-project/llvm/tools/gccld/gccld.cpp

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//===- gccld.cpp - LLVM 'ld' compatible linker ----------------------------===//
//
// This utility is intended to be compatible with GCC, and follows standard
// system 'ld' conventions. As such, the default output file is ./a.out.
// Additionally, this program outputs a shell script that is used to invoke LLI
// to execute the program. In this manner, the generated executable (a.out for
// example), is directly executable, whereas the bytecode file actually lives in
// the a.out.bc file generated by this program. Also, Force is on by default.
//
// Note that if someone (or a script) deletes the executable program generated,
// the .bc file will be left around. Considering that this is a temporary hack,
// I'm not too worried about this.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/Linker.h"
#include "llvm/Module.h"
#include "llvm/PassManager.h"
#include "llvm/Bytecode/Reader.h"
#include "llvm/Bytecode/WriteBytecodePass.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/Scalar.h"
#include "Support/CommandLine.h"
#include "Support/Signals.h"
#include <fstream>
#include <memory>
#include <set>
#include <algorithm>
#include <sys/types.h> // For FileExists
#include <sys/stat.h>
namespace {
cl::list<std::string>
InputFilenames(cl::Positional, cl::desc("<input bytecode files>"),
cl::OneOrMore);
cl::opt<std::string>
OutputFilename("o", cl::desc("Override output filename"), cl::init("a.out"),
cl::value_desc("filename"));
cl::opt<bool>
Verbose("v", cl::desc("Print information about actions taken"));
cl::list<std::string>
LibPaths("L", cl::desc("Specify a library search path"), cl::Prefix,
cl::value_desc("directory"));
cl::list<std::string>
Libraries("l", cl::desc("Specify libraries to link to"), cl::Prefix,
cl::value_desc("library prefix"));
cl::opt<bool>
Strip("s", cl::desc("Strip symbol info from executable"));
cl::opt<bool>
NoInternalize("disable-internalize",
cl::desc("Do not mark all symbols as internal"));
cl::opt<bool>
LinkAsLibrary("link-as-library", cl::desc("Link the .bc files together as a"
" library, not an executable"));
// Compatibility options that are ignored, but support by LD
cl::opt<std::string>
CO3("soname", cl::Hidden, cl::desc("Compatibility option: ignored"));
cl::opt<std::string>
CO4("version-script", cl::Hidden, cl::desc("Compatibility option: ignored"));
cl::opt<bool>
CO5("eh-frame-hdr", cl::Hidden, cl::desc("Compatibility option: ignored"));
cl::opt<bool>
CO6("r", cl::Hidden, cl::desc("Compatibility option: ignored"));
}
// FileExists - Return true if the specified string is an openable file...
static inline bool FileExists(const std::string &FN) {
struct stat StatBuf;
return stat(FN.c_str(), &StatBuf) != -1;
}
// LoadObject - Read the specified "object file", which should not search the
// library path to find it.
static inline std::auto_ptr<Module> LoadObject(std::string FN,
std::string &OutErrorMessage) {
if (Verbose) std::cerr << "Loading '" << FN << "'\n";
if (!FileExists(FN)) {
// Attempt to load from the LLVM_LIB_SEARCH_PATH directory... if we would
// otherwise fail. This is used to locate objects like crtend.o.
//
char *SearchPath = getenv("LLVM_LIB_SEARCH_PATH");
if (SearchPath && FileExists(std::string(SearchPath)+"/"+FN))
FN = std::string(SearchPath)+"/"+FN;
else {
OutErrorMessage = "could not find input file '" + FN + "'!";
return std::auto_ptr<Module>();
}
}
std::string ErrorMessage;
Module *Result = ParseBytecodeFile(FN, &ErrorMessage);
if (Result) return std::auto_ptr<Module>(Result);
OutErrorMessage = "Bytecode file '" + FN + "' corrupt!";
if (ErrorMessage.size()) OutErrorMessage += ": " + ErrorMessage;
return std::auto_ptr<Module>();
}
static Module *LoadSingleLibraryObject(const std::string &Filename) {
std::string ErrorMessage;
std::auto_ptr<Module> M = LoadObject(Filename, ErrorMessage);
if (M.get() == 0 && Verbose) {
std::cerr << "Error loading '" + Filename + "'";
if (!ErrorMessage.empty()) std::cerr << ": " << ErrorMessage;
std::cerr << "\n";
}
return M.release();
}
// IsArchive - Returns true iff FILENAME appears to be the name of an ar
// archive file. It determines this by checking the magic string at the
// beginning of the file.
static bool IsArchive(const std::string &filename) {
std::string ArchiveMagic("!<arch>\012");
char buf[1 + ArchiveMagic.size()];
std::ifstream f(filename.c_str());
f.read(buf, ArchiveMagic.size());
buf[ArchiveMagic.size()] = '\0';
return ArchiveMagic == buf;
}
// LoadLibraryExactName - This looks for a file with a known name and tries to
// load it, similarly to LoadLibraryFromDirectory().
static inline bool LoadLibraryExactName(const std::string &FileName,
std::vector<Module*> &Objects, bool &isArchive) {
if (Verbose) std::cerr << " Considering '" << FileName << "'\n";
if (FileExists(FileName)) {
if (IsArchive(FileName)) {
std::string ErrorMessage;
if (Verbose) std::cerr << " Loading '" << FileName << "'\n";
if (!ReadArchiveFile(FileName, Objects, &ErrorMessage)) {
isArchive = true;
return false; // Success!
}
if (Verbose) {
std::cerr << " Error loading archive '" + FileName + "'";
if (!ErrorMessage.empty()) std::cerr << ": " << ErrorMessage;
std::cerr << "\n";
}
} else {
if (Module *M = LoadSingleLibraryObject(FileName)) {
isArchive = false;
Objects.push_back(M);
return false;
}
}
}
return true;
}
// LoadLibrary - Try to load a library named LIBNAME that contains
// LLVM bytecode. If SEARCH is true, then search for a file named
// libLIBNAME.{a,so,bc} in the current library search path. Otherwise,
// assume LIBNAME is the real name of the library file. This method puts
// the loaded modules into the Objects list, and sets isArchive to true if
// a .a file was loaded. It returns true if no library is found or if an
// error occurs; otherwise it returns false.
//
static inline bool LoadLibrary(const std::string &LibName,
std::vector<Module*> &Objects, bool &isArchive,
bool search, std::string &ErrorMessage) {
if (search) {
// First, try the current directory. Then, iterate over the
// directories in LibPaths, looking for a suitable match for LibName
// in each one.
for (unsigned NextLibPathIdx = 0; NextLibPathIdx != LibPaths.size();
++NextLibPathIdx) {
std::string Directory = LibPaths[NextLibPathIdx] + "/";
if (!LoadLibraryExactName(Directory + "lib" + LibName + ".a",
Objects, isArchive))
return false;
if (!LoadLibraryExactName(Directory + "lib" + LibName + ".so",
Objects, isArchive))
return false;
if (!LoadLibraryExactName(Directory + "lib" + LibName + ".bc",
Objects, isArchive))
return false;
}
} else {
// If they said no searching, then assume LibName is the real name.
if (!LoadLibraryExactName(LibName, Objects, isArchive))
return false;
}
ErrorMessage = "error linking library '-l" + LibName+ "': library not found!";
return true;
}
static void GetAllDefinedSymbols(Module *M,
std::set<std::string> &DefinedSymbols) {
for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
if (I->hasName() && !I->isExternal() && !I->hasInternalLinkage())
DefinedSymbols.insert(I->getName());
for (Module::giterator I = M->gbegin(), E = M->gend(); I != E; ++I)
if (I->hasName() && !I->isExternal() && !I->hasInternalLinkage())
DefinedSymbols.insert(I->getName());
}
// GetAllUndefinedSymbols - This calculates the set of undefined symbols that
// still exist in an LLVM module. This is a bit tricky because there may be two
// symbols with the same name, but different LLVM types that will be resolved to
// each other, but aren't currently (thus we need to treat it as resolved).
//
static void GetAllUndefinedSymbols(Module *M,
std::set<std::string> &UndefinedSymbols) {
std::set<std::string> DefinedSymbols;
UndefinedSymbols.clear(); // Start out empty
for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
if (I->hasName()) {
if (I->isExternal())
UndefinedSymbols.insert(I->getName());
else if (!I->hasInternalLinkage())
DefinedSymbols.insert(I->getName());
}
for (Module::giterator I = M->gbegin(), E = M->gend(); I != E; ++I)
if (I->hasName()) {
if (I->isExternal())
UndefinedSymbols.insert(I->getName());
else if (!I->hasInternalLinkage())
DefinedSymbols.insert(I->getName());
}
// Prune out any defined symbols from the undefined symbols set...
for (std::set<std::string>::iterator I = UndefinedSymbols.begin();
I != UndefinedSymbols.end(); )
if (DefinedSymbols.count(*I))
UndefinedSymbols.erase(I++); // This symbol really is defined!
else
++I; // Keep this symbol in the undefined symbols list
}
static bool LinkLibrary(Module *M, const std::string &LibName,
bool search, std::string &ErrorMessage) {
std::set<std::string> UndefinedSymbols;
GetAllUndefinedSymbols(M, UndefinedSymbols);
if (UndefinedSymbols.empty()) {
if (Verbose) std::cerr << " No symbols undefined, don't link library!\n";
return false; // No need to link anything in!
}
std::vector<Module*> Objects;
bool isArchive;
if (LoadLibrary(LibName, Objects, isArchive, search, ErrorMessage))
return true;
// Figure out which symbols are defined by all of the modules in the .a file
std::vector<std::set<std::string> > DefinedSymbols;
DefinedSymbols.resize(Objects.size());
for (unsigned i = 0; i != Objects.size(); ++i)
GetAllDefinedSymbols(Objects[i], DefinedSymbols[i]);
bool Linked = true;
while (Linked) { // While we are linking in object files, loop.
Linked = false;
for (unsigned i = 0; i != Objects.size(); ++i) {
// Consider whether we need to link in this module... we only need to
// link it in if it defines some symbol which is so far undefined.
//
const std::set<std::string> &DefSymbols = DefinedSymbols[i];
bool ObjectRequired = false;
for (std::set<std::string>::iterator I = UndefinedSymbols.begin(),
E = UndefinedSymbols.end(); I != E; ++I)
if (DefSymbols.count(*I)) {
if (Verbose)
std::cerr << " Found object providing symbol '" << *I << "'...\n";
ObjectRequired = true;
break;
}
// We DO need to link this object into the program...
if (ObjectRequired) {
if (LinkModules(M, Objects[i], &ErrorMessage))
return true; // Couldn't link in the right object file...
// Since we have linked in this object, delete it from the list of
// objects to consider in this archive file.
std::swap(Objects[i], Objects.back());
std::swap(DefinedSymbols[i], DefinedSymbols.back());
Objects.pop_back();
DefinedSymbols.pop_back();
--i; // Do not skip an entry
// The undefined symbols set should have shrunk.
GetAllUndefinedSymbols(M, UndefinedSymbols);
Linked = true; // We have linked something in!
}
}
}
return false;
}
static int PrintAndReturn(const char *progname, const std::string &Message,
const std::string &Extra = "") {
std::cerr << progname << Extra << ": " << Message << "\n";
return 1;
}
int main(int argc, char **argv) {
cl::ParseCommandLineOptions(argc, argv, " llvm linker for GCC\n");
std::string ErrorMessage;
std::auto_ptr<Module> Composite(LoadObject(InputFilenames[0], ErrorMessage));
if (Composite.get() == 0)
return PrintAndReturn(argv[0], ErrorMessage);
// We always look first in the current directory when searching for libraries.
LibPaths.insert(LibPaths.begin(), ".");
// If the user specied an extra search path in their environment, respect it.
if (char *SearchPath = getenv("LLVM_LIB_SEARCH_PATH"))
LibPaths.push_back(SearchPath);
for (unsigned i = 1; i < InputFilenames.size(); ++i) {
// A user may specify an ar archive without -l, perhaps because it
// is not installed as a library. Detect that and link the library.
if (IsArchive(InputFilenames[i])) {
if (Verbose) std::cerr << "Linking archive '" << InputFilenames[i]
<< "'\n";
if (LinkLibrary(Composite.get(), InputFilenames[i], false, ErrorMessage))
return PrintAndReturn(argv[0], ErrorMessage,
": error linking in '" + InputFilenames[i] + "'");
continue;
}
std::auto_ptr<Module> M(LoadObject(InputFilenames[i], ErrorMessage));
if (M.get() == 0)
return PrintAndReturn(argv[0], ErrorMessage);
if (Verbose) std::cerr << "Linking in '" << InputFilenames[i] << "'\n";
if (LinkModules(Composite.get(), M.get(), &ErrorMessage))
return PrintAndReturn(argv[0], ErrorMessage,
": error linking in '" + InputFilenames[i] + "'");
}
// Remove any consecutive duplicates of the same library...
Libraries.erase(std::unique(Libraries.begin(), Libraries.end()),
Libraries.end());
// Link in all of the libraries next...
for (unsigned i = 0; i != Libraries.size(); ++i) {
if (Verbose) std::cerr << "Linking in library: -l" << Libraries[i] << "\n";
if (LinkLibrary(Composite.get(), Libraries[i], true, ErrorMessage))
return PrintAndReturn(argv[0], ErrorMessage);
}
// In addition to just linking the input from GCC, we also want to spiff it up
// a little bit. Do this now.
//
PassManager Passes;
// Add an appropriate TargetData instance for this module...
Passes.add(new TargetData("gccas", Composite.get()));
// Linking modules together can lead to duplicated global constants, only keep
// one copy of each constant...
//
Passes.add(createConstantMergePass());
// If the -s command line option was specified, strip the symbols out of the
// resulting program to make it smaller. -s is a GCC option that we are
// supporting.
//
if (Strip)
Passes.add(createSymbolStrippingPass());
// Often if the programmer does not specify proper prototypes for the
// functions they are calling, they end up calling a vararg version of the
// function that does not get a body filled in (the real function has typed
// arguments). This pass merges the two functions.
//
Passes.add(createFunctionResolvingPass());
if (!NoInternalize) {
// Now that composite has been compiled, scan through the module, looking
// for a main function. If main is defined, mark all other functions
// internal.
//
Passes.add(createInternalizePass());
}
// Remove unused arguments from functions...
//
Passes.add(createDeadArgEliminationPass());
// The FuncResolve pass may leave cruft around if functions were prototyped
// differently than they were defined. Remove this cruft.
//
Passes.add(createInstructionCombiningPass());
// Delete basic blocks, which optimization passes may have killed...
//
Passes.add(createCFGSimplificationPass());
// Now that we have optimized the program, discard unreachable functions...
//
Passes.add(createGlobalDCEPass());
// Add the pass that writes bytecode to the output file...
std::string RealBytecodeOutput = OutputFilename;
if (!LinkAsLibrary) RealBytecodeOutput += ".bc";
std::ofstream Out(RealBytecodeOutput.c_str());
if (!Out.good())
return PrintAndReturn(argv[0], "error opening '" + RealBytecodeOutput +
"' for writing!");
Passes.add(new WriteBytecodePass(&Out)); // Write bytecode to file...
// Make sure that the Out file gets unlink'd from the disk if we get a SIGINT
RemoveFileOnSignal(RealBytecodeOutput);
// Run our queue of passes all at once now, efficiently.
Passes.run(*Composite.get());
Out.close();
if (!LinkAsLibrary) {
// Output the script to start the program...
std::ofstream Out2(OutputFilename.c_str());
if (!Out2.good())
return PrintAndReturn(argv[0], "error opening '" + OutputFilename +
"' for writing!");
Out2 << "#!/bin/sh\nlli -q -abort-on-exception $0.bc $*\n";
Out2.close();
// Make the script executable...
chmod(OutputFilename.c_str(), 0755);
}
return 0;
}
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