tunefs: Don't lower WARNS

[des]

Summary

Use casts to silence the alignment warnings instead of potentially
suppressing other legitimate warnings.

MFC after: 1 week

[jhb]

@brooks, @jrtc27: I wonder if it might be nice to have a __ASSUME_ALIGNED wrapper for these cases similar to __DECONST. In particular, for CHERI it can be useful to annotate when pointer values are properly aligned so that assignment can be inlined instead of resulting in a libcall to memcpy.

[brooks]

__ASSUME_ALIGNED could work. __builtin_assume_aligned is broadly supported so I double we even need a fall back.

[des]

In D56033#1282934, @brooks wrote:

__ASSUME_ALIGNED could work. __builtin_assume_aligned is broadly supported so I double we even need a fall back.

__ASSUME_ALIGNED currently does not exist, may I commit this until it does?

[jhb]

In D56033#1284538, @des wrote:

In D56033#1282934, @brooks wrote:

__ASSUME_ALIGNED could work. __builtin_assume_aligned is broadly supported so I double we even need a fall back.

__ASSUME_ALIGNED currently does not exist, may I commit this until it does?

Yes, to be clear, I wasn't objecting at all, just wanting to raise the idea of being more explicit in the future for these cases.