Optimize linkonce_odr unnamed_addr functions during LTO.

Generalize the API so we can distinguish symbols that are needed just for a DSO
symbol table from those that are used from some native .o.

The symbols that are only wanted for the dso symbol table can be dropped if
llvm can prove every other dso has a copy (linkonce_odr) and the address is not
important (unnamed_addr).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191922 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 39 insertions, 11 deletions

diff --git a/lib/Transforms/IPO/IPO.cpp b/lib/Transforms/IPO/IPO.cpp
index 5d563d8bbf..5f26bac2c8 100644
--- a/lib/Transforms/IPO/IPO.cpp
+++ b/lib/Transforms/IPO/IPO.cpp
@@ -98,7 +98,7 @@ void LLVMAddInternalizePass(LLVMPassManagerRef PM, unsigned AllButMain) {
   std::vector<const char *> Export;
   if (AllButMain)
     Export.push_back("main");
-  unwrap(PM)->add(createInternalizePass(Export));
+  unwrap(PM)->add(createInternalizePass(Export, None));
 }
 
 void LLVMAddStripDeadPrototypesPass(LLVMPassManagerRef PM) {
diff --git a/lib/Transforms/IPO/Internalize.cpp b/lib/Transforms/IPO/Internalize.cpp
index f2feacc0b6..f20a7bd92f 100644
--- a/lib/Transforms/IPO/Internalize.cpp
+++ b/lib/Transforms/IPO/Internalize.cpp
@@ -44,13 +44,20 @@ APIList("internalize-public-api-list", cl::value_desc("list"),
         cl::desc("A list of symbol names to preserve"),
         cl::CommaSeparated);
 
+static cl::list<std::string>
+DSOList("internalize-dso-list", cl::value_desc("list"),
+        cl::desc("A list of symbol names need for a dso symbol table"),
+        cl::CommaSeparated);
+
 namespace {
   class InternalizePass : public ModulePass {
     std::set<std::string> ExternalNames;
+    std::set<std::string> DSONames;
   public:
     static char ID; // Pass identification, replacement for typeid
     explicit InternalizePass();
-    explicit InternalizePass(ArrayRef<const char *> ExportList);
+    explicit InternalizePass(ArrayRef<const char *> ExportList,
+                             ArrayRef<const char *> DSOList);
     void LoadFile(const char *Filename);
     virtual bool runOnModule(Module &M);
 
@@ -71,15 +78,21 @@ InternalizePass::InternalizePass()
   if (!APIFile.empty())           // If a filename is specified, use it.
     LoadFile(APIFile.c_str());
   ExternalNames.insert(APIList.begin(), APIList.end());
+  DSONames.insert(DSOList.begin(), DSOList.end());
 }
 
-InternalizePass::InternalizePass(ArrayRef<const char *> ExportList)
+InternalizePass::InternalizePass(ArrayRef<const char *> ExportList,
+                                 ArrayRef<const char *> DSOList)
   : ModulePass(ID){
   initializeInternalizePassPass(*PassRegistry::getPassRegistry());
   for(ArrayRef<const char *>::const_iterator itr = ExportList.begin();
         itr != ExportList.end(); itr++) {
     ExternalNames.insert(*itr);
   }
+  for(ArrayRef<const char *>::const_iterator itr = DSOList.begin();
+        itr != DSOList.end(); itr++) {
+    DSONames.insert(*itr);
+  }
 }
 
 void InternalizePass::LoadFile(const char *Filename) {
@@ -99,7 +112,8 @@ void InternalizePass::LoadFile(const char *Filename) {
 }
 
 static bool shouldInternalize(const GlobalValue &GV,
-                              const std::set<std::string> &ExternalNames) {
+                              const std::set<std::string> &ExternalNames,
+                              const std::set<std::string> &DSONames) {
   // Function must be defined here
   if (GV.isDeclaration())
     return false;
@@ -116,7 +130,20 @@ static bool shouldInternalize(const GlobalValue &GV,
   if (ExternalNames.count(GV.getName()))
     return false;
 
-  return true;
+  // Not needed for the symbol table?
+  if (!DSONames.count(GV.getName()))
+    return true;
+
+  // Not a linkonce. Someone can depend on it being on the symbol table.
+  if (!GV.hasLinkOnceLinkage())
+    return false;
+
+  // The address is not important, we can hide it.
+  if (GV.hasUnnamedAddr())
+    return true;
+
+  // FIXME: Check if the address is used.
+  return false;
 }
 
 bool InternalizePass::runOnModule(Module &M) {
@@ -145,7 +172,7 @@ bool InternalizePass::runOnModule(Module &M) {
   // Mark all functions not in the api as internal.
   // FIXME: maybe use private linkage?
   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
-    if (!shouldInternalize(*I, ExternalNames))
+    if (!shouldInternalize(*I, ExternalNames, DSONames))
       continue;
 
     I->setLinkage(GlobalValue::InternalLinkage);
@@ -182,7 +209,7 @@ bool InternalizePass::runOnModule(Module &M) {
   // FIXME: maybe use private linkage?
   for (Module::global_iterator I = M.global_begin(), E = M.global_end();
        I != E; ++I) {
-    if (!shouldInternalize(*I, ExternalNames))
+    if (!shouldInternalize(*I, ExternalNames, DSONames))
       continue;
 
     I->setLinkage(GlobalValue::InternalLinkage);
@@ -194,7 +221,7 @@ bool InternalizePass::runOnModule(Module &M) {
   // Mark all aliases that are not in the api as internal as well.
   for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
        I != E; ++I) {
-    if (!shouldInternalize(*I, ExternalNames))
+    if (!shouldInternalize(*I, ExternalNames, DSONames))
       continue;
 
     I->setLinkage(GlobalValue::InternalLinkage);
@@ -210,6 +237,7 @@ ModulePass *llvm::createInternalizePass() {
   return new InternalizePass();
 }
 
-ModulePass *llvm::createInternalizePass(ArrayRef<const char *> ExportList) {
-  return new InternalizePass(ExportList);
+ModulePass *llvm::createInternalizePass(ArrayRef<const char *> ExportList,
+                                        ArrayRef<const char *> DSOList) {
+  return new InternalizePass(ExportList, DSOList);
 }
diff --git a/lib/Transforms/IPO/PassManagerBuilder.cpp b/lib/Transforms/IPO/PassManagerBuilder.cpp
index 2008c5d65e..b9660fab78 100644
--- a/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -277,7 +277,7 @@ void PassManagerBuilder::populateLTOPassManager(PassManagerBase &PM,
   // for a main function.  If main is defined, mark all other functions
   // internal.
   if (Internalize)
-    PM.add(createInternalizePass("main"));
+    PM.add(createInternalizePass("main", None));
 
   // Propagate constants at call sites into the functions they call.  This
   // opens opportunities for globalopt (and inlining) by substituting function