From 7b556ead93561522b88d926230db1bba26a9f62e Mon Sep 17 00:00:00 2001
From: Hans Wennborg <hans@hanshq.net>
Date: Wed, 10 Sep 2014 19:28:48 +0000
Subject: [PATCH] MS ABI: Emit dynamic initializers for selectany globals in
 comdat-associative sections (PR20889)

This prevents initializers for comdat-folded globals from running multiple times.

Differential Revision: http://reviews.llvm.org/D5281

llvm-svn: 217534
---
 clang/lib/CodeGen/CGDeclCXX.cpp               |  5 ++++
 .../microsoft-abi-static-initializers.cpp     | 26 ++++++++++++++-----
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/clang/lib/CodeGen/CGDeclCXX.cpp b/clang/lib/CodeGen/CGDeclCXX.cpp
index af5919c157fd..79a055869274 100644
--- a/clang/lib/CodeGen/CGDeclCXX.cpp
+++ b/clang/lib/CodeGen/CGDeclCXX.cpp
@@ -332,6 +332,11 @@ CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D,
     // COMDAT key is required for correctness.
     AddGlobalCtor(Fn, 65535, Addr);
     DelayedCXXInitPosition.erase(D);
+  } else if (D->hasAttr<SelectAnyAttr>()) {
+    // SelectAny globals will be comdat-folded. Put the initializer into a COMDAT
+    // group associated with the global, so the initializers get folded too.
+    AddGlobalCtor(Fn, 65535, Addr);
+    DelayedCXXInitPosition.erase(D);
   } else {
     llvm::DenseMap<const Decl *, unsigned>::iterator I =
       DelayedCXXInitPosition.find(D);
diff --git a/clang/test/CodeGenCXX/microsoft-abi-static-initializers.cpp b/clang/test/CodeGenCXX/microsoft-abi-static-initializers.cpp
index 5f74c54c1c45..f255ef02a121 100644
--- a/clang/test/CodeGenCXX/microsoft-abi-static-initializers.cpp
+++ b/clang/test/CodeGenCXX/microsoft-abi-static-initializers.cpp
@@ -1,9 +1,12 @@
 // RUN: %clang_cc1 -fms-extensions -emit-llvm %s -o - -mconstructor-aliases -triple=i386-pc-win32 | FileCheck %s
 
-// CHECK: @llvm.global_ctors = appending global [2 x { i32, void ()*, i8* }]
-// CHECK: [{ i32, void ()*, i8* } { i32 65535, void ()* @"\01??__Efoo@?$B@H@@2VA@@A@YAXXZ",
-// CHECK:       i8* bitcast (%class.A* @"\01?foo@?$B@H@@2VA@@A" to i8*) },
-// CHECK:  { i32, void ()*, i8* } { i32 65535, void ()* @_GLOBAL__sub_I_microsoft_abi_static_initializers.cpp, i8* null }]
+// CHECK: @llvm.global_ctors = appending global [5 x { i32, void ()*, i8* }] [
+// CHECK: { i32, void ()*, i8* } { i32 65535, void ()* @"\01??__Eselectany1@@YAXXZ", i8* getelementptr inbounds (%struct.S* @"\01?selectany1@@3US@@A", i32 0, i32 0) },
+// CHECK: { i32, void ()*, i8* } { i32 65535, void ()* @"\01??__Eselectany2@@YAXXZ", i8* getelementptr inbounds (%struct.S* @"\01?selectany2@@3US@@A", i32 0, i32 0) },
+// CHECK: { i32, void ()*, i8* } { i32 65535, void ()* @"\01??__Es@?$ExportedTemplate@H@@2US@@A@YAXXZ", i8* getelementptr inbounds (%struct.S* @"\01?s@?$ExportedTemplate@H@@2US@@A", i32 0, i32 0) },
+// CHECK: { i32, void ()*, i8* } { i32 65535, void ()* @"\01??__Efoo@?$B@H@@2VA@@A@YAXXZ", i8* bitcast (%class.A* @"\01?foo@?$B@H@@2VA@@A" to i8*) },
+// CHECK: { i32, void ()*, i8* } { i32 65535, void ()* @_GLOBAL__sub_I_microsoft_abi_static_initializers.cpp, i8* null }
+// CHECK: ]
 
 struct S {
   S();
@@ -21,8 +24,8 @@ S s;
 // CHECK: call x86_thiscallcc void @"\01??1S@@QAE@XZ"
 // CHECK: ret void
 
-// These globals should use distinct guard variables, and not different bits of
-// the same global.
+// These globals should have initializers comdat associative with the global.
+// See @llvm.global_ctors above.
 __declspec(selectany) S selectany1;
 __declspec(selectany) S selectany2;
 // CHECK: define linkonce_odr void @"\01??__Eselectany1@@YAXXZ"()
@@ -34,9 +37,20 @@ __declspec(selectany) S selectany2;
 // CHECK: call x86_thiscallcc %struct.S* @"\01??0S@@QAE@XZ"
 // CHECK: ret void
 
+// The implicitly instantiated static data member should have initializer
+// comdat associative with the global.
+template <typename T> struct __declspec(dllexport) ExportedTemplate {
+  static S s;
+};
+template <typename T> S ExportedTemplate<T>::s;
+void useExportedTemplate(ExportedTemplate<int> x) {
+  (void)x.s;
+}
+
 void StaticLocal() {
   static S TheS;
 }
+
 // CHECK-LABEL: define void @"\01?StaticLocal@@YAXXZ"()
 // CHECK: load i32* @"\01?$S1@?0??StaticLocal@@YAXXZ@4IA"
 // CHECK: store i32 {{.*}}, i32* @"\01?$S1@?0??StaticLocal@@YAXXZ@4IA"