Merging r339317:

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r339317 | theraven | 2018-08-09 10:02:42 +0200 (Thu, 09 Aug 2018) | 15 lines

Correctly initialise global blocks on Windows.

Summary:
Windows does not allow globals to be initialised to point to globals in
another DLL.  Exported globals may be referenced only from code.  Work
around this by creating an initialiser that runs in early library
initialisation and sets the isa pointer.

Reviewers: rjmccall

Reviewed By: rjmccall

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D50436
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llvm-svn: 339339

1 files changed, 26 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CGBlocks.cpp b/clang/lib/CodeGen/CGBlocks.cpp
index 8269b5b229a..906b98bfbaf 100644
--- a/clang/lib/CodeGen/CGBlocks.cpp
+++ b/clang/lib/CodeGen/CGBlocks.cpp
@@ -1213,9 +1213,13 @@ static llvm::Constant *buildGlobalBlock(CodeGenModule &CGM,
   auto fields = builder.beginStruct();
 
   bool IsOpenCL = CGM.getLangOpts().OpenCL;
+  bool IsWindows = CGM.getTarget().getTriple().isOSWindows();
   if (!IsOpenCL) {
     // isa
-    fields.add(CGM.getNSConcreteGlobalBlock());
+    if (IsWindows)
+      fields.addNullPointer(CGM.Int8PtrPtrTy);
+    else
+      fields.add(CGM.getNSConcreteGlobalBlock());
 
     // __flags
     BlockFlags flags = BLOCK_IS_GLOBAL | BLOCK_HAS_SIGNATURE;
@@ -1250,7 +1254,27 @@ static llvm::Constant *buildGlobalBlock(CodeGenModule &CGM,
 
   llvm::Constant *literal = fields.finishAndCreateGlobal(
       "__block_literal_global", blockInfo.BlockAlign,
-      /*constant*/ true, llvm::GlobalVariable::InternalLinkage, AddrSpace);
+      /*constant*/ !IsWindows, llvm::GlobalVariable::InternalLinkage, AddrSpace);
+
+  // Windows does not allow globals to be initialised to point to globals in
+  // different DLLs.  Any such variables must run code to initialise them.
+  if (IsWindows) {
+    auto *Init = llvm::Function::Create(llvm::FunctionType::get(CGM.VoidTy,
+          {}), llvm::GlobalValue::InternalLinkage, ".block_isa_init",
+        &CGM.getModule());
+    llvm::IRBuilder<> b(llvm::BasicBlock::Create(CGM.getLLVMContext(), "entry",
+          Init));
+    b.CreateAlignedStore(CGM.getNSConcreteGlobalBlock(),
+        b.CreateStructGEP(literal, 0), CGM.getPointerAlign().getQuantity());
+    b.CreateRetVoid();
+    // We can't use the normal LLVM global initialisation array, because we
+    // need to specify that this runs early in library initialisation.
+    auto *InitVar = new llvm::GlobalVariable(CGM.getModule(), Init->getType(),
+        /*isConstant*/true, llvm::GlobalValue::InternalLinkage,
+        Init, ".block_isa_init_ptr");
+    InitVar->setSection(".CRT$XCLa");
+    CGM.addUsedGlobal(InitVar);
+  }
 
   // Return a constant of the appropriately-casted type.
   llvm::Type *RequiredType =