rjmccall added inline comments.
================
Comment at: clang/include/clang/AST/Stmt.h:1104
+ static_assert(sizeof(*this) <= 16,
"changing bitfields changed sizeof(Stmt)");
static_assert(sizeof(*this) % alignof(void *) == 0,
----------------
mibintc wrote:
> rjmccall wrote:
> > What's happening here is exactly what this assertion is supposed to
> > prevent. If you need more bits in one of these classes (I assume it's
> > `CXXOperatorCallExpr`), you need to either make a field in the actual class
> > or investigate more arcane mechanisms like trailing storage to reduce the
> > normal impact. The latter is probably unnecessary for
> > `CXXOperatorCallExpr`.
> @rjmccall The reason i changed the assertion is because FPOptions is now
> wider, so I had to change the assertion. See line 609 above. Is there
> something I need to do differently?
Because `Stmt` is a common base class for so much of the AST but only needs to
store a small amount of state itself, we have a complicated system for
optimizing space usage in subclasses by allocating bit-fields into `Stmt`.
Letting an individual subclass's bit-field usage run over the expected size and
therefore inflate `Stmt` for all subclasses would be counter-productive, hence
the `static_assert` and why it shouldn't be changed. You need to move the
storage of `FPOptions` into the appropriate subclass wherever it would cause
the `static_assert` to fail.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D72841/new/
https://reviews.llvm.org/D72841
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