[PATCH] D125130: [CodeGen] Clarify the semantics of ADDCARRY/SUBCARRY

Sat May 7 13:20:08 PDT 2022

kazu added a comment.

In D125130#3497763 <https://reviews.llvm.org/D125130#3497763>, @efriedma wrote:

> I don't think most people are going to be familiar with "active high"/"active low" terminology.  At least, I had to look it up.

OK.  I've replaced them with "if and only if" phrases.

> I think it makes sense to:
>
> 1. Explicitly mention the relationship with UADDO/USUBO.
> 2. Explicitly call out that for subtraction, the native carry flag is the inverse of what USUBO produces.

I am not sure if the latest revision addresses your comment about UADD/USUBO.  If not, I'd like to drop the last paragraph about [US]{ADD,SUB}O and check in the rest.  I think it's important to check in the precise definition first.  We can always add supplemental information later.  Thanks!

Repository:
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  https://reviews.llvm.org/D125130/new/

https://reviews.llvm.org/D125130