RFC: Update Intel386, x86-64 and IA MCU psABIs for passing/returning empty struct
H.J. Lu via cfe-commits
cfe-commits at lists.llvm.org
Tue Feb 23 06:57:48 PST 2016
On Mon, Feb 22, 2016 at 4:50 AM, Michael Matz <matz at suse.de> wrote:
> On Sat, 20 Feb 2016, Richard Smith wrote:
>> > An empty type is a type where it and all of its subobjects
>> > (recursively) are of class, structure, union, or array type.
>> > doesn't cover "trivially-copyable".
>> That's correct. Whether a type is trivially copyable is unrelated to
>> whether it is empty.
> I would still feel more comfortable to include the restriction to
> trivially copyable types, not in the part of definition of empty type, of
> course, but as part of the restrictions of when a type can be passed in no
> registers. Basically to clarify the intent in the psABI if there's any
> doubt. I.e. like so:
> An empty type is a type where it and all of its subobjects (recursively)
> are of class, structure, union, or array type. No memory slot nor
> register should be used to pass or return an object of empty type that's
> trivially copyable.
> (With possibly a self-sufficient definition of trivially copyable, that's
> language agnostic)
Do you have an example in which an empty type defined above isn't
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