[PATCH] Add a separate llvm.global_ctors entry for linkonce_odr data initializers

[Reid Kleckner]

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.

http://llvm-reviews.chandlerc.com/D1475

Files:
  lib/CodeGen/CGDeclCXX.cpp
  test/CodeGenCXX/microsoft-abi-static-initializers.cpp
  test/CodeGenCXX/static-member-variable-explicit-specialization.cpp

Index: lib/CodeGen/CGDeclCXX.cpp
===================================================================
--- lib/CodeGen/CGDeclCXX.cpp
+++ lib/CodeGen/CGDeclCXX.cpp
@@ -284,6 +284,13 @@
     OrderGlobalInits Key(order, PrioritizedCXXGlobalInits.size());
     PrioritizedCXXGlobalInits.push_back(std::make_pair(Key, Fn));
     DelayedCXXInitPosition.erase(D);
+  } else if (D->getInstantiatedFromStaticDataMember()) {
+    // Initializers of static data members of class template specializations are
+    // not guaranteed to run in any order with respect to the rest of the
+    // initializers in a TU.  As a consequence, we can put them into their own
+    // llvm.global_ctors entry.  This should allow GlobalOpt to fire more often.
+    AddGlobalCtor(Fn);
+    DelayedCXXInitPosition.erase(D);
   } else {
     llvm::DenseMap<const Decl *, unsigned>::iterator I =
       DelayedCXXInitPosition.find(D);
Index: test/CodeGenCXX/microsoft-abi-static-initializers.cpp
===================================================================
--- test/CodeGenCXX/microsoft-abi-static-initializers.cpp
+++ 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();
@@ -130,7 +134,7 @@
   (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 at XZ"
 // CHECK: call i32 @atexit(void ()* @"\01??__Ffoo@?$B at H@@YAXXZ")
 // CHECK: ret void
@@ -145,7 +149,6 @@
 
 // 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 }
Index: test/CodeGenCXX/static-member-variable-explicit-specialization.cpp
===================================================================
--- test/CodeGenCXX/static-member-variable-explicit-specialization.cpp
+++ test/CodeGenCXX/static-member-variable-explicit-specialization.cpp
@@ -1,11 +1,30 @@
 // 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
 template<> int A<char>::a;
 
 // 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
+
+// CHECK: define internal void @__cxx_global_var_init()
+// CHECK: call i32 @foo()
+// CHECK: store {{.*}} @_ZN1AIsE1aE
+// CHECK: ret
 
+// CHECK: define internal void @_GLOBAL__I_a()
+// CHECK: call
+// CHECK: call
+// CHECK-NOT: call
+// CHECK: ret
-------------- next part --------------
A non-text attachment was scrubbed...
Name: D1475.1.patch
Type: text/x-patch
Size: 3338 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20130822/4f1d439f/attachment.bin>