Fix linking of shared libraries.

In shared libraries the plugin can see non-weak declarations that are still
undefined.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226031 91177308-0d34-0410-b5e6-96231b3b80d8

test/tools/gold/emit-llvm.ll

@@ -24,6 +24,8 @@ target triple = "x86_64-unknown-linux-gnu"
 @g7 = extern_weak global i32
 ; CHECK-DAG: @g7 = extern_weak global i32
 
+@g8 = external global i32
+
 ; CHECK: define internal void @f1()
 ; OPT-NOT: @f1
 define hidden void @f1() {
@@ -69,13 +71,19 @@ define i32* @f7() {
   ret i32* @g7
 }
 
+define i32* @f8() {
+  ret i32* @g8
+}
+
 ; API: f1 PREVAILING_DEF_IRONLY
 ; API: f2 PREVAILING_DEF_IRONLY
 ; API: f3 PREVAILING_DEF_IRONLY_EXP
 ; API: f4 PREVAILING_DEF_IRONLY_EXP
 ; API: f5 PREVAILING_DEF_IRONLY_EXP
 ; API: f6 PREVAILING_DEF_IRONLY_EXP
 ; API: f7 PREVAILING_DEF_IRONLY_EXP
+; API: f8 PREVAILING_DEF_IRONLY_EXP
 ; API: g7 UNDEF
+; API: g8 UNDEF
 ; API: g5 PREVAILING_DEF_IRONLY_EXP
 ; API: g6 PREVAILING_DEF_IRONLY_EXP

tools/gold/gold-plugin.cpp

@@ -633,7 +633,7 @@ getModuleForFile(LLVMContext &Context, claimed_file &F, raw_fd_ostream *ApiFile,
       break;
 
     case LDPR_UNDEF:
-      if (!GV->hasExternalWeakLinkage()) {
+      if (!GV->isDeclarationForLinker()) {
         assert(GV->hasComdat());
         Drop.insert(GV);
       }