[llvm-dev] target ABI: call parameters handling

Ulrich Weigand via llvm-dev llvm-dev at lists.llvm.org
Thu Oct 7 10:39:54 PDT 2021

"Reid Kleckner" <rnk at google.com> wrote on 06.10.2021 19:00:44:
> On Wed, Oct 6, 2021 at 9:15 AM Ulrich Weigand <Ulrich.Weigand at de.ibm.com>
>> As I commented in another mail, unfortunately this is not true.
>> To ensure correct codegen in all cases, we need to know *which*
>> extension the callee expects: zero- or sign-extension.  The
>> backend cannot know this without being told by the frontend.

> Maybe this is just a wording thing, but I do believe my statement is
> true: the backend is absolutely free to guess if it wants to, and
> requiring attributes doesn't guarantee correctness. It may just move
> the bug to the frontend. I acknowledge that there are risks to
> guessing. I just think it is important to consider alternative
> designs and weigh the pros and cons.

I guess it's indeed just wording, and we agree on the substance.

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