Add code to GlobalVariable.h so that global variables marked as

externally_initialized return false for hasDefiniteInitializer and
hasUniqueInitializer.

rdar://12580965.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174345 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 44 insertions, 2 deletions

diff --git a/include/llvm/IR/GlobalVariable.h b/include/llvm/IR/GlobalVariable.h
index bf1e891..112a846 100644
--- a/include/llvm/IR/GlobalVariable.h
+++ b/include/llvm/IR/GlobalVariable.h
@@ -110,7 +110,10 @@ public:
     return hasInitializer() &&
       // The initializer of a global variable with weak linkage may change at
       // link time.
-      !mayBeOverridden();
+      !mayBeOverridden() &&
+      // The initializer of a global variable with the externally_initialized
+      // marker may change at runtime before cxx initializers are evaluated.
+      !isExternallyInitialized();
   }
 
   /// hasUniqueInitializer - Whether the global variable has an initializer, and
@@ -123,7 +126,11 @@ public:
       // instead. It is wrong to modify the initializer of a global variable
       // with *_odr linkage because then different instances of the global may
       // have different initializers, breaking the One Definition Rule.
-      !isWeakForLinker();
+      !isWeakForLinker() &&
+      // It is not safe to modify initializers of global variables with the
+      // external_initializer marker since the value may be changed at runtime
+      // before cxx initializers are evaluated.
+      !isExternallyInitialized();
   }
 
   /// getInitializer - Return the initializer for this global variable.  It is
diff --git a/test/Transforms/GlobalOpt/externally-initialized-global-ctr.ll b/test/Transforms/GlobalOpt/externally-initialized-global-ctr.ll
new file mode 100644
index 0000000..f447fe6
--- /dev/null
+++ b/test/Transforms/GlobalOpt/externally-initialized-global-ctr.ll
@@ -0,0 +1,35 @@
+; RUN: opt < %s -globalopt -S | FileCheck %s
+; rdar://12580965.
+; ObjC++ test case.
+
+%struct.ButtonInitData = type { i8* }
+
+@_ZL14buttonInitData = internal global [1 x %struct.ButtonInitData] zeroinitializer, align 4
+
+@"\01L_OBJC_METH_VAR_NAME_40" = internal global [7 x i8] c"print:\00", section "__TEXT,__objc_methname,cstring_literals", align 1
+@"\01L_OBJC_SELECTOR_REFERENCES_41" = internal externally_initialized  global i8* getelementptr inbounds ([7 x i8]* @"\01L_OBJC_METH_VAR_NAME_40", i32 0, i32 0), section "__DATA, __objc_selrefs, literal_pointers, no_dead_strip"
+
+@llvm.global_ctors = appending global [1 x { i32, void ()* }] [{ i32, void ()* } { i32 65535, void ()* @_GLOBAL__I_a }]
+@llvm.used = appending global [2 x i8*] [i8* getelementptr inbounds ([7 x i8]* @"\01L_OBJC_METH_VAR_NAME_40", i32 0, i32 0),  i8* bitcast (i8** @"\01L_OBJC_SELECTOR_REFERENCES_41" to i8*)]
+
+define internal void @__cxx_global_var_init() section "__TEXT,__StaticInit,regular,pure_instructions" {
+  %1 = load i8** @"\01L_OBJC_SELECTOR_REFERENCES_41", !invariant.load !2009
+  store i8* %1, i8** getelementptr inbounds ([1 x %struct.ButtonInitData]* @_ZL14buttonInitData, i32 0, i32 0, i32 0), align 4
+  ret void
+}
+
+define internal void @_GLOBAL__I_a() section "__TEXT,__StaticInit,regular,pure_instructions" {
+  call void @__cxx_global_var_init()
+  ret void
+}
+
+declare void @test(i8*)
+
+define void @print() {
+; CHECK: %1 = load i8** getelementptr inbounds ([1 x %struct.ButtonInitData]* @_ZL14buttonInitData, i32 0, i32 0, i32 0), align 4
+  %1 = load i8** getelementptr inbounds ([1 x %struct.ButtonInitData]* @_ZL14buttonInitData, i32 0, i32 0, i32 0), align 4
+  call void @test(i8* %1)
+  ret void
+}
+
+!2009 = metadata !{}
\ No newline at end of file