[llvm-dev] [RFC] Create llvm/Support/InternalLimits.h

[Philip Reames via llvm-dev]

Seems like a reasonable idea, but we want to be careful to define which 
internal limits are in scope, and which are not.

For instance, ValueTracking has a bunch of internal scope limits for 
analysis purpose.  Moving those into some generic location would seem 
like a mistake.

Your example of alignment is a good one.

As a idea, what if we specifically restricted this to internal limits of 
the IR representation?  Or is that too narrow?  What other specific 
limits are you thinking of?

Philip

On 3/5/21 6:05 AM, David Zarzycki via llvm-dev wrote:
> Hello,
>
> There are internal limits within LLVM that are fundamental to how LLVM operates but are defined in awkward places when it comes to library layering. I'd like to propose that we fix that with a simple "InternalLimits.h" file that contains a few essential constants.
>
> For example, the maximum alignment supported by LLVM is defined by CodeGen but clang's Sema needs to know that value to enforce that users stay within bounds. That being said, clang's Sema doesn't need or want to depend on CodeGen for various good reasons.
>
> If we create llvm/Support/InternalLimits.h and define the alignment limit there, then LLVM's CodeGen and clang's Sema can both include that file without Sema creating a dependency on CodeGen.
>
> Thoughts?
> Dave
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