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Re: [PATCH, pretty-ipa] Fix wave ICE in SRA
Hi,
On Thu, 7 May 2009, Richard Guenther wrote:
> > Âif (TREE_CODE (exp) == COMPONENT_REF)
> > Â Âsize_tree = TYPE_SIZE (TREE_TYPE (TREE_OPERAND (exp, 1)));
> > Âelse if ...and so on...
> >
> > is wrong, it's DECL_SIZE (TREE_OPERAND (exp, 1)).
>
> They should be exchangable in the context of an access.
As pointed out, you always should use DECL_SIZE if available. IMO.
...
May I say that this whole thing looks rather disturbing, mismatching
random mixes of different TYPE_ or DECL_SIZEs on the same assignment can't
be a good sign of a proper intermediate representation. Except for very
good reasons, maybe bitfields, but a simple copy from a base variable ...
IMO that variable shouldn't have had a DECL_SIZE that includes alignment ...
I would understand that TYPE_SIZE includes it (and only for the reason
that constructing arrays of such elements then implicitely includes the
alignment when going from one to the next member).
> At least
> ... = x.a;
> and
>
> p = &x.a;
> ... = *p;
>
> already have different sizes and that better should not matter(?).
Well, if typeof(*p) has larger alignment (and hence TYPE_SIZE) than
typeof(x.a) you have a problem when the end of x.a lies exactly on a page
border for instance, and you want to copy too many bytes. Weren't there
even bugreports about exactly such situation?
(Of course *p shouldn't have larger alignment from the start to not
introduce unaligned accesses, but in that case they also will have the
same TYPE_SIZEs again, so I stay by my nervousness about mismatching
TYPE/DECL_SIZEs)
Ciao,
Michael.