[PATCH] D152140: [Clang] Limit FunctionTypeExtraBitfields::NumExceptionType to 16 bits.

Mon Jun 5 07:05:14 PDT 2023

erichkeane added inline comments.

================
Comment at: clang/include/clang/AST/Type.h:3956
     /// [implimits] 8 bits would be enough here.
-    unsigned NumExceptionType = 0;
+    unsigned NumExceptionType : 16;
+
----------------
sdesmalen wrote:
> erichkeane wrote:
> > tbaeder wrote:
> > > Isn't using a `uint16_t` preferred over a bitfield?
> > Ah, thats a great point, yes, I think that is probably better here!  I like the assert on setting it (particularly because we're shrinking it!), but that idea makes this patch much smaller.
> The reason for making this a bitfield rather than uint16_t is because D127762 extends the struct with another (bit)field:
> 
>     /// Any AArch64 SME ACLE type attributes that need to be propagated
>     /// on declarations and function pointers.
>     unsigned AArch64SMEAttributes : 6;
> 
> I thought having this all be bitfields made more sense, but I'm happy to change it to a uint16_t if that is preferred.
> 
> > that idea makes this patch much smaller
> I suspect that the assert is still required to ensure that the value stored fits the value? Using `uint16_t` doesn't change that, or did I miss something? :)
We don't need them all to be bitfields, they'll take up the same amount of space with out it, and save us a bit of oddity.

I like the assert still as well, but since this size is set in 1 place, an assert there would be fine as well.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D152140/new/

https://reviews.llvm.org/D152140