Add a separate llvm.global_ctors entry for linkonce_odr data initializers
Summary:
These typically come from static data members of class template
specializations. This accomplishes two things:
1. May expose GlobalOpt optimizations for Itanium C++ ABI code.
2. Works toward fixing double initialization in the Microsoft C++ ABI.
CC: cfe-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D1475
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@189051 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGDeclCXX.cpp b/lib/CodeGen/CGDeclCXX.cpp
index d61755c..ff06448 100644
--- a/lib/CodeGen/CGDeclCXX.cpp
+++ b/lib/CodeGen/CGDeclCXX.cpp
@@ -278,6 +278,19 @@
OrderGlobalInits Key(order, PrioritizedCXXGlobalInits.size());
PrioritizedCXXGlobalInits.push_back(std::make_pair(Key, Fn));
DelayedCXXInitPosition.erase(D);
+ } else if (D->getInstantiatedFromStaticDataMember()) {
+ // C++ [basic.start.init]p2:
+ // Defnitions of explicitly specialized class template static data members
+ // have ordered initialization. Other class template static data members
+ // (i.e., implicitly or explicitly instantiated specializations) have
+ // unordered initialization.
+ //
+ // As a consequence, we can put them into their own llvm.global_ctors entry.
+ // This should allow GlobalOpt to fire more often, and allow us to implement
+ // the Microsoft C++ ABI, which uses COMDAT elimination to avoid double
+ // initializaiton.
+ AddGlobalCtor(Fn);
+ DelayedCXXInitPosition.erase(D);
} else {
llvm::DenseMap<const Decl *, unsigned>::iterator I =
DelayedCXXInitPosition.find(D);
diff --git a/test/CodeGenCXX/microsoft-abi-static-initializers.cpp b/test/CodeGenCXX/microsoft-abi-static-initializers.cpp
index 35e343b..56536b1 100644
--- a/test/CodeGenCXX/microsoft-abi-static-initializers.cpp
+++ b/test/CodeGenCXX/microsoft-abi-static-initializers.cpp
@@ -1,5 +1,9 @@
// RUN: %clang_cc1 -emit-llvm %s -o - -cxx-abi microsoft -triple=i386-pc-win32 | FileCheck %s
+// CHECK: @llvm.global_ctors = appending global [2 x { i32, void ()* }]
+// CHECK: [{ i32, void ()* } { i32 65535, void ()* [[INIT_foo:@.*global_var.*]] },
+// CHECK: { i32, void ()* } { i32 65535, void ()* @_GLOBAL__I_a }]
+
struct S {
S() {}
~S() {}
@@ -33,7 +37,7 @@
(void)B<int>::foo; // (void) - force usage
}
-// CHECK: define internal void [[INIT_foo:@.*global_var.*]] [[NUW]]
+// CHECK: define internal void [[INIT_foo]]() [[NUW]]
// CHECK: %{{[.0-9A-Z_a-z]+}} = call x86_thiscallcc %class.A* @"\01??0A@@QAE@XZ"
// CHECK: call i32 @atexit(void ()* [[FOO_DTOR:@"__dtor_.*foo@.*]])
// CHECK: ret void
@@ -48,7 +52,6 @@
// CHECK: define internal void @_GLOBAL__I_a() [[NUW]] {
// CHECK: call void [[INIT_s]]
-// CHECK: call void [[INIT_foo]]
// CHECK: ret void
// CHECK: attributes [[NUW]] = { nounwind }
diff --git a/test/CodeGenCXX/static-member-variable-explicit-specialization.cpp b/test/CodeGenCXX/static-member-variable-explicit-specialization.cpp
index 94fd9aa..e499efd 100644
--- a/test/CodeGenCXX/static-member-variable-explicit-specialization.cpp
+++ b/test/CodeGenCXX/static-member-variable-explicit-specialization.cpp
@@ -1,5 +1,6 @@
// RUN: %clang_cc1 %s -triple=x86_64-apple-darwin10 -emit-llvm -o - | FileCheck %s
// CHECK: ; ModuleID
+
template<typename> struct A { static int a; };
// CHECK-NOT: @_ZN1AIcE1aE
@@ -8,4 +9,28 @@
// CHECK: @_ZN1AIbE1aE = global i32 10
template<> int A<bool>::a = 10;
+// CHECK: @llvm.global_ctors = appending global [2 x { i32, void ()* }]
+// CHECK: [{ i32, void ()* } { i32 65535, void ()* @__cxx_global_var_init },
+// CHECK: { i32, void ()* } { i32 65535, void ()* @_GLOBAL__I_a }]
+extern "C" int foo();
+template<> int A<short>::a = foo(); // Separate global_ctor entry
+int b = foo(); // Goes in _GLOBAL__I_a
+int c = foo(); // Goes in _GLOBAL__I_a
+
+// An explicit specialization is ordered, and goes in __GLOBAL_I_a.
+template<> struct A<int> { static int a; };
+int A<int>::a = foo();
+
+// CHECK: define internal void @__cxx_global_var_init()
+// CHECK: call i32 @foo()
+// CHECK: store {{.*}} @_ZN1AIsE1aE
+// CHECK: ret
+
+// CHECK: define internal void @_GLOBAL__I_a()
+// We call unique stubs for every ordered dynamic initializer in the TU.
+// CHECK: call
+// CHECK: call
+// CHECK: call
+// CHECK-NOT: call
+// CHECK: ret