zoecarver added inline comments.
================
Comment at: clang/lib/Sema/SemaDeclCXX.cpp:6502
+ // except that it has a non-trivial member *with* the trivial_abi attribute.
+ for (auto Base : D->bases()) {
+ if (auto CxxRecord = Base.getType()->getAsCXXRecordDecl())
----------------
ahatanak wrote:
> It looks like this patch changes the way `D` is passed in the following code:
>
> ```
> struct B {
> int i[4];
> B();
> B(const B &) = default;
> B(B &&);
> };
>
> struct D : B {
> D();
> D(const D &) = default;
> D(D &&) = delete;
> };
>
> void testB(B a);
> void testD(D a);
>
> void testCallB() {
> B b;
> testB(b);
> }
>
> void testCallD() {
> D d;
> testD(d);
> }
> ```
>
> `B` cannot be passed in registers because it has a non-trivial move
> constructor, whereas `D` can be passed in registers because the move
> constructor is deleted and the copy constructor is trivial.
>
> I'm not sure what the best way to handle this is, but I just wanted to point
> this out.
Hmm. Good catch. One way to fix this would be to simply create a
`HasPassableSubobject` variable and add that to the conditions below (instead
of returning false here). But, it seems that `D` isn't passed by registers
(even though, maybe it should be) on ToT: https://godbolt.org/z/4xevW5
Given that, do you think it's OK to return false here, or should I update this
patch to use the logic I just described (even though that would be a nfc)?
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D92361/new/
https://reviews.llvm.org/D92361
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