Null pointer check elimination

Sat Nov 12 06:54:00 GMT 2005

David Daney <ddaney@avtrex.com> writes:
> > Eventually we should manually mark certain function DECLs as
> > not-returning-null instead of my kludgy test for this one case. I don't
> > know if/when I can get to that. Perhaps somebody else can take it from
> > here.
>> Looks like all the bits in struct tree_common are used up.
>> Q: Would it make sense to add a flag to struct tree_decl_common to
> indicate !zero, set it using an attribute, (and automatically in the
> java front-end for the cases above), and then test for it in
> tree-vrp.c similar to below?

This should be done using an attribute, yes. If this is going to be
tested frequently enough, it would make sense to add a bit to struct
tree_function_decl (I don't see any reason to put it in struct
tree_decl-common) (there is currently room for one more bit in
tree_function_decl on a machine which requires 16-bit alignment, or 17
more bits on a machine which requires 32-bit alignment). Note that it
is also possible to simply store the attribute on DECL_ATTRIBUTES and
look it up using lookup_attribute.
Ian