From 880e8c0ad41345f353b819c51092baa8f05e1950 Mon Sep 17 00:00:00 2001
From: Lang Hames <lhames@gmail.com>
Date: Mon, 4 Mar 2013 22:40:44 +0000
Subject: [PATCH] Check isDiscardableIfUnused, rather than hasLocalLinkage,
 when bumping GlobalValue linkage up to ExternalLinkage in the ExtractGV pass.
 This prevents linkonce and linkonce_odr symbols from being DCE'd.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176459 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/IPO/ExtractGV.cpp |  6 +++---
 test/Other/extract-linkonce.ll   | 23 +++++++++++++++++++++++
 2 files changed, 26 insertions(+), 3 deletions(-)
 create mode 100644 test/Other/extract-linkonce.ll

diff --git a/lib/Transforms/IPO/ExtractGV.cpp b/lib/Transforms/IPO/ExtractGV.cpp
index 8a6bfc6d885..fa3d72ddcf1 100644
--- a/lib/Transforms/IPO/ExtractGV.cpp
+++ b/lib/Transforms/IPO/ExtractGV.cpp
@@ -60,7 +60,7 @@ namespace {
             continue;
         }
 
-        bool Local = I->hasLocalLinkage();
+        bool Local = I->isDiscardableIfUnused();
         if (Local)
           I->setVisibility(GlobalValue::HiddenVisibility);
 
@@ -80,7 +80,7 @@ namespace {
             continue;
         }
 
-        bool Local = I->hasLocalLinkage();
+        bool Local = I->isDiscardableIfUnused();
         if (Local)
           I->setVisibility(GlobalValue::HiddenVisibility);
 
@@ -97,7 +97,7 @@ namespace {
         Module::alias_iterator CurI = I;
         ++I;
 
-        if (CurI->hasLocalLinkage()) {
+        if (CurI->isDiscardableIfUnused()) {
           CurI->setVisibility(GlobalValue::HiddenVisibility);
           CurI->setLinkage(GlobalValue::ExternalLinkage);
         }
diff --git a/test/Other/extract-linkonce.ll b/test/Other/extract-linkonce.ll
new file mode 100644
index 00000000000..31fbf3ac463
--- /dev/null
+++ b/test/Other/extract-linkonce.ll
@@ -0,0 +1,23 @@
+; 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.
+
+; CHECK:      @bar = external hidden global i32
+; CHECK:      define hidden i32* @foo() {
+; CHECK-NEXT:  ret i32* @bar
+; CHECK-NEXT: }
+
+; DELETE: @bar = hidden global i32 42
+; DELETE: declare hidden i32* @foo()
+
+@bar = linkonce global i32 42
+
+define linkonce i32* @foo() {
+  ret i32* @bar
+}
+
+define void @g() {
+  call i32* @foo()
+  ret void
+}