ahatanak added a comment. In D96832#2569481 <https://reviews.llvm.org/D96832#2569481>, @zequanwu wrote:
> In D96832#2568257 <https://reviews.llvm.org/D96832#2568257>, @aaron.ballman > wrote: > >> It was explicitly disallowed in the initial patch: >> https://reviews.llvm.org/D12922 and the original author said "I'm still >> trying to figure out the best way to handle c++ virtual functions: this >> attribute is not very useful for someone who is looking for a way to >> reliably prevent tail-call to a virtual function." and "I made this change >> because this attribute isn't useful when the compiler cannot resolve the >> function call statically at compile time and it isn't important for the use >> case I have." Has this situation changed in the backend? > > Oh, I didn't see that. But when I tested `not_tail_called` on normal > functions, it seems like not working(https://godbolt.org/z/znr5b5, `f1` is > marked as `not_tail_called`, it still get inlined). Or, I misunderstand how > to use it properly? I'm still trying to remember the discussions we had, but I think we banned the attribute on virtual functions because you can't in general promise a call to an annotated function won't be tail called if the function is virtual. This patch doesn't prevent the call to `method` in the code below from being tail called, but I suppose users would except the attribute to prevent the tail call? struct B { virtual void method(); }; struct D : B { [[clang::not_tail_called]] void method() override; }; void test(D *d) { B *b = D; b->method(); } Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D96832/new/ https://reviews.llvm.org/D96832 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
