[PATCH] D108643: Introduce _BitInt, deprecate _ExtInt

Tue Sep 14 07:50:14 PDT 2021

aaron.ballman added a comment.

In D108643#2991995 <https://reviews.llvm.org/D108643#2991995>, @hjl.tools wrote:

>>> The choice that high bits are unspecified rather than extended is an interesting one.  Can you speak to that?  That's good for +, -, *, &, |, ^, <<, and narrowing conversions, but bad for ==, <, /, >>, and widening conversions.
>>
>> I've added @hjl.tools to the review for his opinions, as he was the primary driver for the x64 ABI proposal. HJ, can you help me out here?
>
> Please follow up x86-64 psABI proposal with any feedbacks:
>
> https://groups.google.com/g/x86-64-abi/c/XQiSj-zU3w8

We don't have feedback yet, @hjl.tools; we're asking for rationale on the behavior of unused bits in the proposed psABI for x86-64. Can you help us understand why the bits are unspecified rather than extended and whether there are potential performance concerns from this decision (before it gets solidified)? Thanks!

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D108643/new/

https://reviews.llvm.org/D108643