[PATCH] D156136: [BPF] Clean up SelLowering

[Tamir Duberstein via Phabricator via llvm-commits]

tamird added a comment.

In D156136#4545381 <https://reviews.llvm.org/D156136#4545381>, @yonghong-song wrote:

> The error message is not what I envisioned.
>
>   $ cat t.c
>   struct t {
>      int a;
>   };
>   struct t foo(int a, int b) {
>     struct t tmp;
>     tmp.a = a + b;
>     return tmp;
>   }
>   $ clang --target=bpf -O2 -g -c t.c
>   t.c:4:10: error: functions returning through a pointer parameter are not supported
>       4 | struct t foo(int a, int b) {
>         |          ^
>   1 error generated.
>   $
>
> From source code perspective, there is no 'returning through a pointer parameter'.
> The source code shows 'returning a struct'.
> The error message can be 'functions returning a struct are not supported'.
>
> 'union' has the same issue,
>
>   $ cat t.c
>   union t {
>      int a;
>      int b;
>   };
>   union t foo(int a, int b) {
>     union t tmp;
>     tmp.a = a + b;
>     return tmp;
>   }
>   $ clang --target=bpf -O2 -g -c t.c
>   t.c:5:9: error: functions returning through a pointer parameter are not supported
>       5 | union t foo(int a, int b) {
>         |         ^
>   1 error generated.
>   $
>
> In llvm IR, 'union' is represented as 'struct' as well.
>
> If you really want, the error message can be
> `functions returning a struct/union are not supported`.

Good point; I changed this wording to match the return-struct-in-registers wording. I was trying to distinguish these messages, but there's no need, they are the same from the user's perspective.


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  https://reviews.llvm.org/D156136/new/

https://reviews.llvm.org/D156136