[llvm] r195470 - Convert linkonce* to weak* instead of strong.

[Rafael Espindola]

Author: rafael
Date: Fri Nov 22 10:14:30 2013
New Revision: 195470

URL: http://llvm.org/viewvc/llvm-project?rev=195470&view=rev
Log:
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.

Modified:
    llvm/trunk/lib/Transforms/IPO/ExtractGV.cpp
    llvm/trunk/test/Other/extract-linkonce.ll

Modified: llvm/trunk/lib/Transforms/IPO/ExtractGV.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/ExtractGV.cpp?rev=195470&r1=195469&r2=195470&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/ExtractGV.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/ExtractGV.cpp Fri Nov 22 10:14:30 2013
@@ -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();

Modified: llvm/trunk/test/Other/extract-linkonce.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Other/extract-linkonce.ll?rev=195470&r1=195469&r2=195470&view=diff
==============================================================================
--- llvm/trunk/test/Other/extract-linkonce.ll (original)
+++ llvm/trunk/test/Other/extract-linkonce.ll Fri Nov 22 10:14:30 2013
@@ -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