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Re: Fix PR 33870

On Wed, 14 Nov 2007, Diego Novillo wrote:

> Richard Guenther wrote:
> > Bootstrap and regtest on x86_64-unknown-linux-gnu in progress, I intend
> > to commit this if that (as expected) finishes successfully.
> No, let me study this first.

We can also add one additional optimization and sanity check.  In
add_virtual_operand instead of dispatching to add_vars_for_offset for
every SFT in the NMT just do so for those that have
SFT_BASE_FOR_COMPONENTS_P set.  All others can (should) be only directly
dereferenced which means offset has to be zero.  If not, we should
visit them during one of the add_vars_for_offset calls.  This avoids
redundant calls to append_vuse/vdef (so it's merely a compile-time

         /* For SFTs we have to consider all subvariables of the parent 
             if it is a potential points-to location.  */
          if (TREE_CODE (al) == STRUCT_FIELD_TAG
              && TREE_CODE (var) == NAME_MEMORY_TAG)
              if (SFT_BASE_FOR_COMPONENTS_P (al))
                none_added &= !add_vars_for_offset (al, offset, size,
                                                    flags & opf_def);
              else if (offset == 0)
                  /* If this is a SFT that cannot be used as a base for
                     component references, we only need to consider them
                     if offset is zero.  Otherwise if it is aliased via
                     a component ref we will visit it during processing
                     of a SFT_BASE_FOR_COMPONENTS_P pointed-to SFT.
                     In this case just add this SFT as a possible direct
                     dereference target.  */
                  if (flags & opf_def)
                    append_vdef (al);
                    append_vuse (al);
                  none_added = false;

I guess we don't want to do this as part of the initial patch, but I'll
check the compile-time effects if the above works out.


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