From 437dc6082910fda186545ef41338f57935ed9ccb Mon Sep 17 00:00:00 2001
From: Reid Kleckner <reid@kleckner.net>
Date: Wed, 23 Apr 2014 18:22:11 +0000
Subject: [PATCH] MS ABI: Use a different guard variable for each weak global

We were using the same guard variable and failing to initialize the
second global.

Clang is still not MS ABI compatible in this area.  Fixing that is
PR16959, which will require LLVM changes to @llvm.global_ctors.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@207008 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/MicrosoftCXXABI.cpp               | 27 +++++++++++--------
 .../microsoft-abi-static-initializers.cpp     | 13 ++++++++-
 2 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/lib/CodeGen/MicrosoftCXXABI.cpp b/lib/CodeGen/MicrosoftCXXABI.cpp
index 9832969b57..528cdf6238 100644
--- a/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -1273,10 +1273,14 @@ void MicrosoftCXXABI::EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
   llvm::ConstantInt *Zero = llvm::ConstantInt::get(GuardTy, 0);
 
   // Get the guard variable for this function if we have one already.
-  GuardInfo &GI = GuardVariableMap[D.getDeclContext()];
+  GuardInfo EmptyGuardInfo;
+  GuardInfo *GI = &EmptyGuardInfo;
+  if (isa<FunctionDecl>(D.getDeclContext())) {
+    GI = &GuardVariableMap[D.getDeclContext()];
+  }
 
   unsigned BitIndex;
-  if (D.isExternallyVisible()) {
+  if (D.isStaticLocal() && D.isExternallyVisible()) {
     // Externally visible variables have to be numbered in Sema to properly
     // handle unreachable VarDecls.
     BitIndex = getContext().getStaticLocalNumber(&D);
@@ -1284,18 +1288,18 @@ void MicrosoftCXXABI::EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
     BitIndex--;
   } else {
     // Non-externally visible variables are numbered here in CodeGen.
-    BitIndex = GI.BitIndex++;
+    BitIndex = GI->BitIndex++;
   }
 
   if (BitIndex >= 32) {
     if (D.isExternallyVisible())
       ErrorUnsupportedABI(CGF, "more than 32 guarded initializations");
     BitIndex %= 32;
-    GI.Guard = 0;
+    GI->Guard = 0;
   }
 
   // Lazily create the i32 bitfield for this function.
-  if (!GI.Guard) {
+  if (!GI->Guard) {
     // Mangle the name for the guard.
     SmallString<256> GuardName;
     {
@@ -1306,11 +1310,12 @@ void MicrosoftCXXABI::EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
 
     // Create the guard variable with a zero-initializer.  Just absorb linkage
     // and visibility from the guarded variable.
-    GI.Guard = new llvm::GlobalVariable(CGM.getModule(), GuardTy, false,
-                                     GV->getLinkage(), Zero, GuardName.str());
-    GI.Guard->setVisibility(GV->getVisibility());
+    GI->Guard =
+        new llvm::GlobalVariable(CGM.getModule(), GuardTy, false,
+                                 GV->getLinkage(), Zero, GuardName.str());
+    GI->Guard->setVisibility(GV->getVisibility());
   } else {
-    assert(GI.Guard->getLinkage() == GV->getLinkage() &&
+    assert(GI->Guard->getLinkage() == GV->getLinkage() &&
            "static local from the same function had different linkage");
   }
 
@@ -1322,7 +1327,7 @@ void MicrosoftCXXABI::EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
 
   // Test our bit from the guard variable.
   llvm::ConstantInt *Bit = llvm::ConstantInt::get(GuardTy, 1U << BitIndex);
-  llvm::LoadInst *LI = Builder.CreateLoad(GI.Guard);
+  llvm::LoadInst *LI = Builder.CreateLoad(GI->Guard);
   llvm::Value *IsInitialized =
       Builder.CreateICmpNE(Builder.CreateAnd(LI, Bit), Zero);
   llvm::BasicBlock *InitBlock = CGF.createBasicBlock("init");
@@ -1332,7 +1337,7 @@ void MicrosoftCXXABI::EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
   // Set our bit in the guard variable and emit the initializer and add a global
   // destructor if appropriate.
   CGF.EmitBlock(InitBlock);
-  Builder.CreateStore(Builder.CreateOr(LI, Bit), GI.Guard);
+  Builder.CreateStore(Builder.CreateOr(LI, Bit), GI->Guard);
   CGF.EmitCXXGlobalVarDeclInit(D, GV, PerformInit);
   Builder.CreateBr(EndBlock);
 
diff --git a/test/CodeGenCXX/microsoft-abi-static-initializers.cpp b/test/CodeGenCXX/microsoft-abi-static-initializers.cpp
index 021356e8fa..0d336cf42c 100644
--- a/test/CodeGenCXX/microsoft-abi-static-initializers.cpp
+++ b/test/CodeGenCXX/microsoft-abi-static-initializers.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -emit-llvm %s -o - -mconstructor-aliases -triple=i386-pc-win32 | FileCheck %s
+// 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 ()* }]
 // CHECK: [{ i32, void ()* } { i32 65535, void ()* @"\01??__Efoo@?$B@H@@2VA@@A@YAXXZ"
@@ -20,6 +20,17 @@ 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.
+__declspec(selectany) S selectany1;
+__declspec(selectany) S selectany2;
+// CHECK: define internal void @"\01??__Eselectany1@@YAXXZ"() [[NUW:#[0-9]+]]
+// CHECK: load i32* @"\01??_Bselectany1@@3US@@A@5"
+// CHECK: ret void
+// CHECK: define internal void @"\01??__Eselectany2@@YAXXZ"() [[NUW:#[0-9]+]]
+// CHECK: load i32* @"\01??_Bselectany2@@3US@@A@5"
+// CHECK: ret void
+
 void StaticLocal() {
   static S TheS;
 }
-- 
2.40.0