[PATCH] D100257: [VPlan] Add VPUserID to distinguish between recipes and others.

[Gil Rapaport via Phabricator via llvm-commits]

gilr added inline comments.


================
Comment at: llvm/lib/Transforms/Vectorize/VPlanValue.h:276
 
+static_assert(sizeof(VPUser) <= 48, "size of VPUser changed");
+
----------------
fhahn wrote:
> a.elovikov wrote:
> > 1) Why is that important? Do we rely on it or is it simply to prevent uncontrolled growth?
> > 2) Why do we expect it to be the same on 32/64-bit platforms? Don't we have any pointers inside the object? I'd expect the vtable itself would make it different...
> > Why is that important? Do we rely on it or is it simply to prevent uncontrolled growth?
> 
> It's just to prevent accidental growth, but it is not strictly necessary (and we don't have static asserts for other sizes yet), but it is a common pattern, e.g. in various key classes in Clang to prevent unnoticed size growth.
> 
> > Why do we expect it to be the same on 32/64-bit platforms?
> 
> I think `48` should be the upper bound on 64 bit platforms (unless there are differences caused by different 64 bit operating systems) and on 32-bit platforms it should be less than or equal.
This seems a bit premature. Perhaps better to have this discussion separate of this patch.


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  https://reviews.llvm.org/D100257/new/

https://reviews.llvm.org/D100257