[cfe-dev] Checking if function have been emitted

[Piotr Padlewski via cfe-dev]

2017-01-03 16:42 GMT+01:00 John McCall <rjmccall at apple.com>:

>
> On Jan 3, 2017, at 7:23 AM, Piotr Padlewski <piotr.padlewski at gmail.com>
> wrote:
>
> Maybe there is something I am missing, but I though vtables are being
> generated at the end of translation unit.
> If there is nothing clang emits after vtable (maybe except inline virtual
> functions if they are reffered by vtable), then if there is a direct call
> to inline function, the function has to be emitted before
> vtables.
>
>
> This is a fixed-point(-ish) problem: emitting a v-table can require more
> virtual functions which can require more v-tables.  So we just add stuff to
> queues and drain all the queues in a loop.
>
> I would like to emit available_externally vtable only if all inline
> virtual functions has been emitted.
> It seems that I find function like virtual default destructor, that should
> be emitted before vtables (because there is implicit destructor call), but
> isDeclaration() return true for it.
>
>
> You cannot rely on exact order like this in the normal emission code.
> IRGen does not and will not guarantee it.
>
> You could make a separate pass after the lazy-emission loop.
>
> John.
>
> Thanks John, that would make sense. By 'separate pass' you mean do it in
CodeGenModule::Release?

Piotr


>
> Test case like:
>
> struct A {
>   virtual void foo();
>   virtual ~A() {};
> };
>
> void test() {
>   A a; // This will force emit of A's destructor.
> }
>
>
>
>
> 2017-01-03 3:55 GMT+01:00 Mehdi Amini <mehdi.amini at apple.com>:
>
>>
>> > On Dec 30, 2016, at 10:38 AM, Piotr Padlewski via cfe-dev <
>> cfe-dev at lists.llvm.org> wrote:
>> >
>> > Hi,
>> > I would like to check if there is inline virtual function that was not
>> emitted.
>> >
>> > I tried to do something like this based on
>> CodeGenModule::GetOrCreateLLVMFunction:
>> >
>> >       StringRef Name = CGM.getMangledName(VFunction);
>> >       auto *Entry = CGM.GetGlobalValue(Name);
>> >
>> >       // If function doesn't exist or doesn't have a definition.
>> >       if (!Entry || Entry->isDeclaration())
>> >         return true;
>> >
>> > But Entry->isDeclaration() returns True for functions that I would
>> expect to be emited.
>> > What is the proper way of checking that?
>>
>> isDeclaration() only returns true for a function that does not have a
>> body / hasn’t been materialized yet. Do you observe that it is not the case
>> in practice? Or are you trying to look if a function will be emitted by
>> clang but hasn’t already?
>>
>> —
>> Mehdi
>>
>>
>
>
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