Initial implementation of llvm-ld: stolen from gccld.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16305 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 419 insertions, 0 deletions

diff --git a/tools/llvm-ld/Linker.cpp b/tools/llvm-ld/Linker.cpp
new file mode 100644
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+//===- Linker.cpp - Link together LLVM objects and libraries --------------===//
+// 
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// 
+//===----------------------------------------------------------------------===//
+//
+// This file contains routines to handle linking together LLVM bytecode files,
+// and to handle annoying things like static libraries.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm-ld.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 "llvm/Support/Linker.h"
+#include "llvm/Config/config.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/FileUtilities.h"
+#include "llvm/System/Signals.h"
+#include "llvm/Support/SystemUtils.h"
+#include <algorithm>
+#include <fstream>
+#include <memory>
+#include <set>
+using namespace llvm;
+
+/// FindLib - Try to convert Filename into the name of a file that we can open,
+/// if it does not already name a file we can open, by first trying to open
+/// Filename, then libFilename.[suffix] for each of a set of several common
+/// library suffixes, in each of the directories in Paths and the directory
+/// named by the value of the environment variable LLVM_LIB_SEARCH_PATH. Returns
+/// an empty string if no matching file can be found.
+///
+std::string llvm::FindLib(const std::string &Filename,
+                          const std::vector<std::string> &Paths,
+                          bool SharedObjectOnly) {
+  // Determine if the pathname can be found as it stands.
+  if (FileOpenable(Filename))
+    return Filename;
+
+  // If that doesn't work, convert the name into a library name.
+  std::string LibName = "lib" + Filename;
+
+  // Iterate over the directories in Paths to see if we can find the library
+  // there.
+  for (unsigned Index = 0; Index != Paths.size(); ++Index) {
+    std::string Directory = Paths[Index] + "/";
+
+    if (!SharedObjectOnly && FileOpenable(Directory + LibName + ".bc"))
+      return Directory + LibName + ".bc";
+
+    if (FileOpenable(Directory + LibName + SHLIBEXT))
+      return Directory + LibName + SHLIBEXT;
+
+    if (!SharedObjectOnly && FileOpenable(Directory + LibName + ".a"))
+      return Directory + LibName + ".a";
+  }
+
+  // One last hope: Check LLVM_LIB_SEARCH_PATH.
+  char *SearchPath = getenv("LLVM_LIB_SEARCH_PATH");
+  if (SearchPath == NULL)
+    return std::string();
+
+  LibName = std::string(SearchPath) + "/" + LibName;
+  if (FileOpenable(LibName))
+    return LibName;
+
+  return std::string();
+}
+
+/// GetAllDefinedSymbols - Modifies its parameter DefinedSymbols to contain the
+/// name of each externally-visible symbol defined in M.
+///
+void llvm::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 - 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).
+///
+/// Inputs:
+///  M - The module in which to find undefined symbols.
+///
+/// Outputs:
+///  UndefinedSymbols - A set of C++ strings containing the name of all
+///                     undefined symbols.
+///
+void
+llvm::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
+}
+
+
+/// LoadObject - Read in and parse the bytecode file named by FN and return the
+/// module it contains (wrapped in an auto_ptr), or 0 and set ErrorMessage if an
+/// error occurs.
+///
+std::auto_ptr<Module> llvm::LoadObject(const std::string &FN,
+                                       std::string &ErrorMessage) {
+  std::string ParserErrorMessage;
+  Module *Result = ParseBytecodeFile(FN, &ParserErrorMessage);
+  if (Result) return std::auto_ptr<Module>(Result);
+  ErrorMessage = "Bytecode file '" + FN + "' could not be loaded";
+  if (ParserErrorMessage.size()) ErrorMessage += ": " + ParserErrorMessage;
+  return std::auto_ptr<Module>();
+}
+
+/// LinkInArchive - opens an archive library and link in all objects which
+/// provide symbols that are currently undefined.
+///
+/// Inputs:
+///  M        - The module in which to link the archives.
+///  Filename - The pathname of the archive.
+///  Verbose  - Flags whether verbose messages should be printed.
+///
+/// Outputs:
+///  ErrorMessage - A C++ string detailing what error occurred, if any.
+///
+/// Return Value:
+///  TRUE  - An error occurred.
+///  FALSE - No errors.
+///
+static bool LinkInArchive(Module *M,
+                          const std::string &Filename,
+                          std::string &ErrorMessage,
+                          bool Verbose)
+{
+  // Find all of the symbols currently undefined in the bytecode program.
+  // If all the symbols are defined, the program is complete, and there is
+  // no reason to link in any archive files.
+  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!
+  }
+
+  // Load in the archive objects.
+  if (Verbose) std::cerr << "  Loading archive file '" << Filename << "'\n";
+  std::vector<Module*> Objects;
+  if (ReadArchiveFile(Filename, Objects, &ErrorMessage))
+    return true;
+
+  // Figure out which symbols are defined by all of the modules in the archive.
+  std::vector<std::set<std::string> > DefinedSymbols;
+  DefinedSymbols.resize(Objects.size());
+  for (unsigned i = 0; i != Objects.size(); ++i) {
+    GetAllDefinedSymbols(Objects[i], DefinedSymbols[i]);
+  }
+
+  // While we are linking in object files, loop.
+  bool Linked = true;
+  while (Linked) {     
+    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;
+
+      //
+      // If the object defines main() and the program currently has main()
+      // undefined, then automatically link in the module.  Otherwise, look to
+      // see if it defines a symbol that is currently undefined.
+      //
+      if ((M->getMainFunction() == NULL) &&
+          ((DefSymbols.find ("main")) != DefSymbols.end())) {
+        ObjectRequired = true;
+      } else {
+        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 '"
+                        << Objects[i]->getModuleIdentifier ()
+                        << "' 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;
+}
+
+/// LinkInFile - opens a bytecode file and links in all objects which
+/// provide symbols that are currently undefined.
+///
+/// Inputs:
+///  HeadModule - The module in which to link the bytecode file.
+///  Filename   - The pathname of the bytecode file.
+///  Verbose    - Flags whether verbose messages should be printed.
+///
+/// Outputs:
+///  ErrorMessage - A C++ string detailing what error occurred, if any.
+///
+/// Return Value:
+///  TRUE  - An error occurred.
+///  FALSE - No errors.
+///
+static bool LinkInFile(Module *HeadModule,
+                       const std::string &Filename,
+                       std::string &ErrorMessage,
+                       bool Verbose)
+{
+  std::auto_ptr<Module> M(LoadObject(Filename, ErrorMessage));
+  if (M.get() == 0) return true;
+  bool Result = LinkModules(HeadModule, M.get(), &ErrorMessage);
+  if (Verbose) std::cerr << "Linked in bytecode file '" << Filename << "'\n";
+  return Result;
+}
+
+/// LinkFiles - takes a module and a list of files and links them all together.
+/// It locates the file either in the current directory, as its absolute
+/// or relative pathname, or as a file somewhere in LLVM_LIB_SEARCH_PATH.
+///
+/// Inputs:
+///  progname   - The name of the program (infamous argv[0]).
+///  HeadModule - The module under which all files will be linked.
+///  Files      - A vector of C++ strings indicating the LLVM bytecode filenames
+///               to be linked.  The names can refer to a mixture of pure LLVM
+///               bytecode files and archive (ar) formatted files.
+///  Verbose    - Flags whether verbose output should be printed while linking.
+///
+/// Outputs:
+///  HeadModule - The module will have the specified LLVM bytecode files linked
+///               in.
+///
+/// Return value:
+///  FALSE - No errors.
+///  TRUE  - Some error occurred.
+///
+bool llvm::LinkFiles(const char *progname, Module *HeadModule,
+                     const std::vector<std::string> &Files, bool Verbose) {
+  // String in which to receive error messages.
+  std::string ErrorMessage;
+
+  // Full pathname of the file
+  std::string Pathname;
+
+  // Get the library search path from the environment
+  char *SearchPath = getenv("LLVM_LIB_SEARCH_PATH");
+
+  for (unsigned i = 0; i < Files.size(); ++i) {
+    // Determine where this file lives.
+    if (FileOpenable(Files[i])) {
+      Pathname = Files[i];
+    } else {
+      if (SearchPath == NULL) {
+        std::cerr << progname << ": Cannot find linker input file '"
+                  << Files[i] << "'\n";
+        std::cerr << progname
+                  << ": Warning: Your LLVM_LIB_SEARCH_PATH is unset.\n";
+        return true;
+      }
+
+      Pathname = std::string(SearchPath)+"/"+Files[i];
+      if (!FileOpenable(Pathname)) {
+        std::cerr << progname << ": Cannot find linker input file '"
+                  << Files[i] << "'\n";
+        return true;
+      }
+    }
+
+    // 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(Pathname)) {
+      if (Verbose)
+        std::cerr << "Trying to link archive '" << Pathname << "'\n";
+
+      if (LinkInArchive(HeadModule, Pathname, ErrorMessage, Verbose)) {
+        std::cerr << progname << ": Error linking in archive '" << Pathname 
+                  << "': " << ErrorMessage << "\n";
+        return true;
+      }
+    } else if (IsBytecode(Pathname)) {
+      if (Verbose)
+        std::cerr << "Trying to link bytecode file '" << Pathname << "'\n";
+
+      if (LinkInFile(HeadModule, Pathname, ErrorMessage, Verbose)) {
+        std::cerr << progname << ": Error linking in bytecode file '"
+                  << Pathname << "': " << ErrorMessage << "\n";
+        return true;
+      }
+    }
+  }
+
+  return false;
+}
+
+/// LinkLibraries - takes the specified library files and links them into the
+/// main bytecode object file.
+///
+/// Inputs:
+///  progname   - The name of the program (infamous argv[0]).
+///  HeadModule - The module into which all necessary libraries will be linked.
+///  Libraries  - The list of libraries to link into the module.
+///  LibPaths   - The list of library paths in which to find libraries.
+///  Verbose    - Flags whether verbose messages should be printed.
+///  Native     - Flags whether native code is being generated.
+///
+/// Outputs:
+///  HeadModule - The module will have all necessary libraries linked in.
+///
+/// Return value:
+///  FALSE - No error.
+///  TRUE  - Error.
+///
+void llvm::LinkLibraries(const char *progname, Module *HeadModule,
+                         const std::vector<std::string> &Libraries,
+                         const std::vector<std::string> &LibPaths,
+                         bool Verbose, bool Native) {
+  // String in which to receive error messages.
+  std::string ErrorMessage;
+
+  for (unsigned i = 0; i < Libraries.size(); ++i) {
+    // Determine where this library lives.
+    std::string Pathname = FindLib(Libraries[i], LibPaths);
+    if (Pathname.empty()) {
+      // If the pathname does not exist, then continue to the next one if
+      // we're doing a native link and give an error if we're doing a bytecode
+      // link.
+      if (!Native) {
+        std::cerr << progname << ": WARNING: Cannot find library -l"
+                  << Libraries[i] << "\n";
+        continue;
+      }
+    }
+
+    // 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(Pathname)) {
+      if (Verbose)
+        std::cerr << "Trying to link archive '" << Pathname << "' (-l"
+                  << Libraries[i] << ")\n";
+
+      if (LinkInArchive(HeadModule, Pathname, ErrorMessage, Verbose)) {
+        std::cerr << progname << ": " << ErrorMessage
+                  << ": Error linking in archive '" << Pathname << "' (-l"
+                  << Libraries[i] << ")\n";
+        exit(1);
+      }
+    } else if (IsBytecode(Pathname)) {
+      if (Verbose)
+        std::cerr << "Trying to link bytecode file '" << Pathname
+                  << "' (-l" << Libraries[i] << ")\n";
+
+      if (LinkInFile(HeadModule, Pathname, ErrorMessage, Verbose)) {
+        std::cerr << progname << ": " << ErrorMessage
+                  << ": error linking in bytecode file '" << Pathname << "' (-l"
+                  << Libraries[i] << ")\n";
+        exit(1);
+      }
+    }
+  }
+}