From 64f2f910bd48c123a6b5945ebe90b018f7bea4d5 Mon Sep 17 00:00:00 2001
From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Sat, 20 Jul 2013 23:33:15 +0000
Subject: [PATCH] Don't crash when llvm.compiler.used becomes empty.

GlobalOpt simplifies llvm.compiler.used by removing any members that are also
in the more strict llvm.used. Handle the special case where llvm.compiler.used
becomes empty.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186778 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/IPO/GlobalOpt.cpp           |  5 +++++
 test/Transforms/GlobalOpt/compiler-used.ll | 16 ++++++++++++++++
 2 files changed, 21 insertions(+)
 create mode 100644 test/Transforms/GlobalOpt/compiler-used.ll

diff --git a/lib/Transforms/IPO/GlobalOpt.cpp b/lib/Transforms/IPO/GlobalOpt.cpp
index 669162cb3d8..183a599bc12 100644
--- a/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/lib/Transforms/IPO/GlobalOpt.cpp
@@ -3070,6 +3070,11 @@ static int compareNames(const void *A, const void *B) {
 
 static void setUsedInitializer(GlobalVariable &V,
                                SmallPtrSet<GlobalValue *, 8> Init) {
+  if (Init.empty()) {
+    V.eraseFromParent();
+    return;
+  }
+
   SmallVector<llvm::Constant *, 8> UsedArray;
   PointerType *Int8PtrTy = Type::getInt8PtrTy(V.getContext());
 
diff --git a/test/Transforms/GlobalOpt/compiler-used.ll b/test/Transforms/GlobalOpt/compiler-used.ll
new file mode 100644
index 00000000000..a710d272edc
--- /dev/null
+++ b/test/Transforms/GlobalOpt/compiler-used.ll
@@ -0,0 +1,16 @@
+; RUN: opt < %s -globalopt -S | FileCheck %s
+
+; Test that when all members of llvm.compiler.used are found to be redundant
+; we delete it instead of crashing.
+
+define void @foo() {
+  ret void
+}
+
+@llvm.used = appending global [1 x i8*] [i8* bitcast (void ()* @foo to i8*)], section "llvm.metadata"
+
+@llvm.compiler.used = appending global [1 x i8*] [i8* bitcast (void ()* @foo to i8*)], section "llvm.metadata"
+
+; CHECK-NOT: @llvm.compiler.used
+; CHECK: @llvm.used = appending global [1 x i8*] [i8* bitcast (void ()* @foo to i8*)], section "llvm.metadata"
+; CHECK-NOT: @llvm.compiler.used