[PATCH] D106701: [clang] Add -falign-loops=N where N is a power of 2

[Fangrui Song via Phabricator via llvm-commits]

MaskRay added a comment.

In D106701#2902544 <https://reviews.llvm.org/D106701#2902544>, @dblaikie wrote:

> In D106701#2901656 <https://reviews.llvm.org/D106701#2901656>, @MaskRay wrote:
>
>> In D106701#2901639 <https://reviews.llvm.org/D106701#2901639>, @efriedma wrote:
>>
>>> Can we hook this up to a LLVM IR function attribute, instead of making it a codegen flag?
>>
>> The current TargetLoweringBase::PrefLoopAlignment is global. I have considered a function attribute, but it seems overkill for now.
>> (Inlining behavior is a bit unclear.)
>> The current use cases just need a global value instead of a refined per-function value.
>
> global module metadata is also an option

Using a global module metadata needs to think of the merging behavior.
The behavior isn't clear.

> (what's the motivation for adding this feature - do you have a use-case in mind?)

Use case: x86 has a `cl::opt`. RISC-V is exploring D106570 <https://reviews.llvm.org/D106570>.

> (the usual: This should probably be committed as separate patches - at least LLVM, then Clang pieces)

(Can commit the llvm/ part first.)


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