[cfe-commits] r153723 - in /cfe/trunk: lib/CodeGen/CGDecl.cpp lib/CodeGen/ItaniumCXXABI.cpp test/CodeGenCXX/static-init.cpp

[Eli Friedman]

On Thu, Mar 29, 2012 at 9:46 PM, John McCall <rjmccall at apple.com> wrote:
> On Mar 29, 2012, at 9:41 PM, Eli Friedman wrote:
>> On Thu, Mar 29, 2012 at 9:25 PM, John McCall <rjmccall at apple.com> wrote:
>>> Author: rjmccall
>>> Date: Thu Mar 29 23:25:14 2012
>>> New Revision: 153723
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=153723&view=rev
>>> Log:
>>> When emitting a static local variable in C++, handle
>>> the case that the variable already exists.  Partly this is just
>>> protection against people making crazy declarations with custom
>>> asm labels or extern "C" names that intentionally collide with
>>> the manglings of such variables, but the main reason is that we
>>> can actually emit a static local variable twice with the
>>> requirement that it match up.  There may be other cases with
>>> (e.g.) the various nested functions, but the main exemplar is
>>> with constructor variants, where we can be forced into
>>> double-emitting the function body under certain circumstances
>>> like (currently) the presence of virtual bases.
>>>
>>> Modified:
>>>    cfe/trunk/lib/CodeGen/CGDecl.cpp
>>>    cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp
>>>    cfe/trunk/test/CodeGenCXX/static-init.cpp
>>>
>>> Modified: cfe/trunk/lib/CodeGen/CGDecl.cpp
>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGDecl.cpp?rev=153723&r1=153722&r2=153723&view=diff
>>> ==============================================================================
>>> --- cfe/trunk/lib/CodeGen/CGDecl.cpp (original)
>>> +++ cfe/trunk/lib/CodeGen/CGDecl.cpp Thu Mar 29 23:25:14 2012
>>> @@ -184,6 +184,24 @@
>>>     Name = GetStaticDeclName(*this, D, Separator);
>>>
>>>   llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(Ty);
>>> +
>>> +  // In C++, there are strange possibilities here involving the
>>> +  // double-emission of constructors and destructors.
>>> +  if (CGM.getLangOpts().CPlusPlus) {
>>> +    llvm::GlobalValue *value = CGM.getModule().getNamedValue(Name);
>>> +    if (value && isa<llvm::GlobalVariable>(value) &&
>>> +        value->getType() ==
>>> +          LTy->getPointerTo(CGM.getContext().getTargetAddressSpace(Ty)))
>>> +      return cast<llvm::GlobalVariable>(value);
>>
>> This check won't work reliably: the global's type isn't guaranteed to
>> be the same as the IR type of the variable.
>
> Is there a situation you have in mind where the type check I've got would
> be inadequate?

B::B() {
  union U { void* x; long double y; };
  static U u = { (void*)&u };
}

-Eli