[PATCH] D76526: Add an algorithm for performing "optimal" layout of a struct.

[John McCall via Phabricator via llvm-commits]

rjmccall added a comment.

In D76526#2689767 <https://reviews.llvm.org/D76526#2689767>, @dblaikie wrote:

> In D76526#2689041 <https://reviews.llvm.org/D76526#2689041>, @lxfind wrote:
>
>> In D76526#2688002 <https://reviews.llvm.org/D76526#2688002>, @dblaikie wrote:
>>
>>> Out of curiosity, what's the motivating use case for the fixed offset fields in this tool?
>>
>> There is a need for this in coroutines. In the coroutine frame layout, the first few fields are fixed according to C++ standard.
>
> Ah, makes sense - is that only for prefixes, or can that result in arbitrary non-initial-sequence fixed offset fields too?

It does support filling holes between fixed fields, yes.  This is actually currently used in coroutines with over-aligned promises that require padding.  (Apparently we are currently putting the padding in the wrong place, but that doesn't deeply matter, since in either case there's padding we can fill.)


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https://reviews.llvm.org/D76526