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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195470 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/IPO/ExtractGV.cpp b/lib/Transforms/IPO/ExtractGV.cpp
index fa3d72ddcf163f12f86dcdd4c4f510402ec14960..07b05ee38a133c988edae2614afa9e569e961407 100644 (file)
--- a/lib/Transforms/IPO/ExtractGV.cpp
+++ b/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();

diff --git a/test/Other/extract-linkonce.ll b/test/Other/extract-linkonce.ll
index 31fbf3ac46327f4fec04f644ac669da78e06009d..4c6b6b76a4abf10f43c1b885eb5ace45c8110b83 100644 (file)
--- a/test/Other/extract-linkonce.ll
+++ b/test/Other/extract-linkonce.ll
@@ -1,15 +1,16 @@
 ; RUN: llvm-extract -func foo -S < %s | FileCheck %s
 ; RUN: llvm-extract -delete -func foo -S < %s | FileCheck --check-prefix=DELETE %s
 
-; Test that we don't convert weak_odr to external definitions.
+; Test that linkonce definitions are mapped to weak so that they are not
+; dropped.
 
-; CHECK:      @bar = external hidden global i32
-; CHECK:      define hidden i32* @foo() {
+; CHECK:      @bar = external global i32
+; CHECK:      define weak i32* @foo() {
 ; CHECK-NEXT:  ret i32* @bar
 ; CHECK-NEXT: }
 
-; DELETE: @bar = hidden global i32 42
-; DELETE: declare hidden i32* @foo()
+; DELETE: @bar = weak global i32 42
+; DELETE: declare i32* @foo()
 
 @bar = linkonce global i32 42