Convert linkonce* to weak* instead of strong.

Also refactor the logic into a helper function. This is an important improvement
on mingw where the linker complains about mixed weak and strong symbols.
Converting to weak ensures that the symbol is not dropped, but keeps in a
comdat, making the linker happy.

llvm-svn: 195470

1 files changed, 37 insertions, 17 deletions

diff --git a/llvm/lib/Transforms/IPO/ExtractGV.cpp b/llvm/lib/Transforms/IPO/ExtractGV.cpp
index fa3d72ddcf1..07b05ee38a1 100644
--- a/llvm/lib/Transforms/IPO/ExtractGV.cpp
+++ b/llvm/lib/Transforms/IPO/ExtractGV.cpp
@@ -21,6 +21,38 @@
 #include <algorithm>
 using namespace llvm;
 
+/// Make sure GV is visible from both modules. Delete is true if it is
+/// being deleted from this module.
+/// This also makes sure GV cannot be dropped so that references from
+/// the split module remain valid.
+static void makeVisible(GlobalValue &GV, bool Delete) {
+  bool Local = GV.hasLocalLinkage();
+  if (Local)
+    GV.setVisibility(GlobalValue::HiddenVisibility);
+
+  if (Local || Delete) {
+    GV.setLinkage(GlobalValue::ExternalLinkage);
+    return;
+  }
+
+  if (!GV.hasLinkOnceLinkage()) {
+    assert(!GV.isDiscardableIfUnused());
+    return;
+  }
+
+  // Map linkonce* to weak* so that llvm doesn't drop this GV.
+  switch(GV.getLinkage()) {
+  default:
+    llvm_unreachable("Unexpected linkage");
+  case GlobalValue::LinkOnceAnyLinkage:
+    GV.setLinkage(GlobalValue::WeakAnyLinkage);
+    return;
+  case GlobalValue::LinkOnceODRLinkage:
+    GV.setLinkage(GlobalValue::WeakODRLinkage);
+    return;
+  }
+}
+
 namespace {
   /// @brief A pass to extract specific functions and their dependencies.
   class GVExtractorPass : public ModulePass {
@@ -60,12 +92,7 @@ namespace {
             continue;
         }
 
-        bool Local = I->isDiscardableIfUnused();
-        if (Local)
-          I->setVisibility(GlobalValue::HiddenVisibility);
-
-        if (Local || Delete)
-          I->setLinkage(GlobalValue::ExternalLinkage);
+	makeVisible(*I, Delete);
 
         if (Delete)
           I->setInitializer(0);
@@ -80,12 +107,7 @@ namespace {
             continue;
         }
 
-        bool Local = I->isDiscardableIfUnused();
-        if (Local)
-          I->setVisibility(GlobalValue::HiddenVisibility);
-
-        if (Local || Delete)
-          I->setLinkage(GlobalValue::ExternalLinkage);
+	makeVisible(*I, Delete);
 
         if (Delete)
           I->deleteBody();
@@ -97,12 +119,10 @@ namespace {
         Module::alias_iterator CurI = I;
         ++I;
 
-        if (CurI->isDiscardableIfUnused()) {
-          CurI->setVisibility(GlobalValue::HiddenVisibility);
-          CurI->setLinkage(GlobalValue::ExternalLinkage);
-        }
+	bool Delete = deleteStuff == (bool)Named.count(CurI);
+	makeVisible(*I, Delete);
 
-        if (deleteStuff == (bool)Named.count(CurI)) {
+        if (Delete) {
           Type *Ty =  CurI->getType()->getElementType();
 
           CurI->removeFromParent();