Replace DepLibs bitcode record with metadata

It keeps the same Module interface as the existing/old deplibs feature, but populates the library list from the metadata after reading the bitcode/LL into the Module.
Keeping the same module interface will allow us to keep the existing uses (e.g. in the gold plugin) as they are.
Internally it still uses the LibraryList variable, but uses it basically as a cache backed by the metadata.

BUG=

Review URL: https://codereview.chromium.org/11615013

1 files changed, 54 insertions, 9 deletions

diff --git a/lib/VMCore/Module.cpp b/lib/VMCore/Module.cpp
index e6e7d99afb..206445ee13 100644
--- a/lib/VMCore/Module.cpp
+++ b/lib/VMCore/Module.cpp
@@ -56,6 +56,7 @@ Module::~Module() {
   GlobalList.clear();
   FunctionList.clear();
   AliasList.clear();
+  LibraryList.clear(); // @LOCALMOD
   NamedMDList.clear();
   delete ValSymTab;
   delete static_cast<StringMap<NamedMDNode *> *>(NamedMDSymTab);
@@ -451,12 +452,59 @@ void Module::dropAllReferences() {
     I->dropAllReferences();
 }
 
-
 // @LOCALMOD-BEGIN
-// TODO(pdox):
-// If possible, use actual bitcode records instead of NamedMetadata.
-// This is contingent upon whether we can get these changes upstreamed
-// immediately, to avoid creating incompatibilities in the bitcode format.
+void Module::convertMetadataToLibraryList() {
+  LibraryList.clear();
+  // Get the DepLib node
+  NamedMDNode *Node = getNamedMetadata("DepLibs");
+  if (!Node)
+    return;
+  for (unsigned i = 0; i < Node->getNumOperands(); i++) {
+    MDString* Mds = dyn_cast_or_null<MDString>(
+        Node->getOperand(i)->getOperand(0));
+    assert(Mds && "Bad NamedMetadata operand");
+    LibraryList.push_back(Mds->getString());
+  }
+  // Clear the metadata so the linker won't try to merge it
+  Node->dropAllReferences();
+}
+
+void Module::convertLibraryListToMetadata() const {
+  if (LibraryList.size() == 0)
+    return;
+  // Get the DepLib node
+  NamedMDNode *Node = getNamedMetadata("DepLibs");
+  assert(Node && "DepLibs metadata node missing");
+  // Erase all existing operands
+  Node->dropAllReferences();
+  // Add all libraries from the library list
+  for (Module::lib_iterator I = lib_begin(), E = lib_end(); I != E; ++I) {
+    MDString *value = MDString::get(getContext(), *I);
+    Node->addOperand(MDNode::get(getContext(),
+                                 makeArrayRef(static_cast<Value*>(value))));
+  }
+}
+
+void Module::addLibrary(StringRef Lib) {
+  for (Module::lib_iterator I = lib_begin(), E = lib_end(); I != E; ++I)
+    if (*I == Lib)
+      return;
+  LibraryList.push_back(Lib);
+  // If the module previously had no deplibs, it may not have the metadata node.
+  // Ensure it exists now, so that we don't have to create it in
+  // convertLibraryListToMetadata (which is const)
+  getOrInsertNamedMetadata("DepLibs");
+}
+
+void Module::removeLibrary(StringRef Lib) {
+  LibraryListType::iterator I = LibraryList.begin();
+  LibraryListType::iterator E = LibraryList.end();
+  for (;I != E; ++I)
+    if (*I == Lib) {
+      LibraryList.erase(I);
+      return;
+    }
+}
 
 static std::string
 ModuleMetaGet(const Module *module, StringRef MetaName) {
@@ -559,12 +607,11 @@ Module::dumpMeta(raw_ostream &OS) const {
   }
   OS << "\n";
   OS << "SOName: " << getSOName() << "\n";
-  /* Commented out until we put lib_iterator back
   for (Module::lib_iterator L = lib_begin(),
                             E = lib_end();
        L != E; ++L) {
     OS << "NeedsLibrary: " << (*L) << "\n";
-    }*/
+  }
   std::vector<NeededRecord> NList;
   getNeededRecords(&NList);
   for (unsigned i = 0; i < NList.size(); ++i) {
@@ -622,12 +669,10 @@ static void getNeededRecordFor(const Module *M,
 // Place the complete list of needed records in NeededOut.
 void Module::getNeededRecords(std::vector<NeededRecord> *NeededOut) const {
   // Iterate through the libraries needed, grabbing each NeededRecord.
-  /* commented out until we pub lib_iterator back
   for (lib_iterator I = lib_begin(), E = lib_end(); I != E; ++I) {
     NeededRecord NR;
     getNeededRecordFor(this, *I, &NR);
     NeededOut->push_back(NR);
   }
-  */
 }
 // @LOCALMOD-END