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).

llvm-svn: 191922

3 files changed, 18 insertions, 1 deletions

diff --git a/llvm/tools/gold/gold-plugin.cpp b/llvm/tools/gold/gold-plugin.cpp
index bd11d1b5556..119631cfa7e 100644
--- a/llvm/tools/gold/gold-plugin.cpp
+++ b/llvm/tools/gold/gold-plugin.cpp
@@ -197,7 +197,7 @@ ld_plugin_status onload(ld_plugin_tv *tv) {
       case LDPT_ADD_SYMBOLS:
         add_symbols = tv->tv_u.tv_add_symbols;
         break;
-      case LDPT_GET_SYMBOLS:
+      case LDPT_GET_SYMBOLS_V2:
         get_symbols = tv->tv_u.tv_get_symbols;
         break;
       case LDPT_ADD_INPUT_FILE:
@@ -386,6 +386,11 @@ static ld_plugin_status all_symbols_read_hook(void) {
 
         if (options::generate_api_file)
           api_file << I->syms[i].name << "\n";
+      } else if (I->syms[i].resolution == LDPR_PREVAILING_DEF_IRONLY_EXP) {
+        lto_codegen_add_dso_symbol(code_gen, I->syms[i].name);
+
+        if (options::generate_api_file)
+          api_file << I->syms[i].name << " dso only\n";
       }
     }
   }
diff --git a/llvm/tools/llvm-lto/llvm-lto.cpp b/llvm/tools/llvm-lto/llvm-lto.cpp
index 3ecd13f5c71..1d03fa62a87 100644
--- a/llvm/tools/llvm-lto/llvm-lto.cpp
+++ b/llvm/tools/llvm-lto/llvm-lto.cpp
@@ -50,6 +50,10 @@ ExportedSymbols("exported-symbol",
   cl::desc("Symbol to export from the resulting object file"),
   cl::ZeroOrMore);
 
+static cl::list<std::string>
+DSOSymbols("dso-symbol",
+  cl::desc("Symbol to put in the symtab in the resulting dso"),
+  cl::ZeroOrMore);
 
 int main(int argc, char **argv) {
   // Print a stack trace if we signal out.
@@ -117,6 +121,10 @@ int main(int argc, char **argv) {
   for (unsigned i = 0; i < ExportedSymbols.size(); ++i)
     CodeGen.addMustPreserveSymbol(ExportedSymbols[i].c_str());
 
+  // Add all the dso symbols to the table of symbols to expose.
+  for (unsigned i = 0; i < DSOSymbols.size(); ++i)
+    CodeGen.addDSOSymbol(DSOSymbols[i].c_str());
+
   if (!OutputFilename.empty()) {
     size_t len = 0;
     std::string ErrorInfo;
diff --git a/llvm/tools/lto/lto.cpp b/llvm/tools/lto/lto.cpp
index 7bfddcd9ec4..a3acd4c9506 100644
--- a/llvm/tools/lto/lto.cpp
+++ b/llvm/tools/lto/lto.cpp
@@ -260,6 +260,10 @@ void lto_codegen_add_must_preserve_symbol(lto_code_gen_t cg,
   cg->addMustPreserveSymbol(symbol);
 }
 
+void lto_codegen_add_dso_symbol(lto_code_gen_t cg, const char *symbol) {
+  cg->addDSOSymbol(symbol);
+}
+
 /// lto_codegen_write_merged_modules - Writes a new file at the specified path
 /// that contains the merged contents of all modules added so far. Returns true
 /// on error (check lto_get_error_message() for details).