Re: [ tree-ssa] PRE problem

[Daniel Berlin <dberlin at dberlin dot org>]

On Feb 20, 2004, at 12:50 PM, Daniel Berlin wrote:

> > Seems reasonable.
> >
> > The problem is we do this substitution (reverse copy propagation) 
> > *without*
> > fixing up the annotation for method_signature.3.  Specifically, if we 
> > do this
> > kind of substitution we need to fix is_dereferenced_{load,store} and
> > type_mem_tag in method_signature.3's annotation.
>
> This is not copy propagation code.
> It's verifying the safety of a rename.
> We don't actually use the generated expressions except to check their 
> versions in the part you are quoting.

We do, however, insert these expressions later if their safety has been 
verified (IE there are two uses of generate_expr_as_of_bb, but the 
changes you've made make no sense for the first, and main, use)
> So i'm not sure what problem this causes for you.
> Are we actually generating and *inserting* an illegal expression?

And if we are generating and inserting an illegal expression , please 
provide me a preprocessed testcase and i'll be happy to make sure the 
rename algorithm doesn't mark it as safe.
--Dan