commit 438900938c3ac9d7fac2dd5d2c85ca4b9b2e35f7
author Rafael Espindola <rafael.espindola@gmail.com> Thu Oct 03 18:29:09 2013 +0000
committer Rafael Espindola <rafael.espindola@gmail.com> Thu Oct 03 18:29:09 2013 +0000
tree ee292d94cfa7c8661cc4cd598f32e66289df9aeb
parent 1df59ef1aa271a4e33cf8973e14bcaf55c585231

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

lib/Transforms/IPO/Internalize.cpp

diff --git a/lib/Transforms/IPO/Internalize.cpp b/lib/Transforms/IPO/Internalize.cpp
index f2feacc..f20a7bd 100644
--- a/lib/Transforms/IPO/Internalize.cpp
+++ b/lib/Transforms/IPO/Internalize.cpp
@@ -44,13 +44,20 @@
         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 @@
   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 @@
 }
 
 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 @@
   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 @@
   // 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 @@
   // 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 @@
   // 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 @@
   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);
 }