On Fri, Jan 25, 2013 at 9:46 AM, Sudakshina Das
<sudakshina1...@gmail.com> wrote:
>
> On Thu, Jan 24, 2013 at 5:15 PM, Richard Biener
> <richard.guent...@gmail.com> wrote:
> >
> > On Thu, Jan 24, 2013 at 7:06 AM, Sudakshina Das
> > <sudakshina1...@gmail.com> wrote:
> > > Dear all,
> > >
> > > I am currently updating a pass that was made for gcc-4.6.*, so that it
> > > works for gcc.4.7.2.
> > >
> > > In the pass for gcc-4.6.*, a code fragment from tree-ssa-structalias.c
> > > was picked up and used.
> > > Given below is the fragment taken form create_function_info_for () .
> > > This fragment was used to create variable information for the function
> > > and it was picked up to perform a similar operation in the added pass
> > > as well.
> > >
> > > But in gcc-4.7.2 some changes are introduced in the fragment. The code
> > > given below shows the changes that have been introduced in
> > > create_function_info_for () of tree-ssa-structalias.c in gcc-4.7.2
> > > along with the original code in the comments.
> > >
> > > /* Add one representative for all further args. */
> > > if (is_varargs)
> > > {
> > > varinfo_t argvi;
> > > const char *newname;
> > > char *tempname;
> > > tree decl;
> > >
> > > asprintf (&tempname, "%s.varargs", name);
> > > newname = ggc_strdup (tempname);
> > > free (tempname);
> > >
> > > /* We need sth that can be pointed to for va_start. */
> > >
> > > /**************** CHANGED CODE in GCC-4.7.2 ***************/
> > > decl = build_fake_var_decl (ptr_type_node);
> > >
> > > /************ ORIGINAL CODE in GCC-4.6.2 *******************
> > > /* decl = create_tmp_var_raw (ptr_type_node, name);
> > > get_var_ann (decl);
> > > */
> > >
> > > argvi = new_var_info (decl, newname);
> > > argvi->offset = fi_parm_base + num_args;
> > > argvi->size = ~0;
> > > argvi->is_full_var = true;
> > > argvi->is_heap_var = true;
> > > argvi->fullsize = vi->fullsize;
> > > gcc_assert (prev_vi->offset < argvi->offset);
> > > prev_vi->next = argvi;
> > > prev_vi = argvi;
> > > }
> > >
> > > return vi;
> > >
> > >
> > > So I made the same changes in the pass where this fragment was used.
> > > But after making the changes the pass is now giving an "internal
> > > compiler error" and a "segmentation fault" at runtime.
> > >
> > > After debugging I could narrow it down to the function
> > > build_fake_var_decl() and to be specific at the memory allocation
> > > statement highlighted below.
> > >
> > >
> > > tree
> > > build_fake_var_decl (tree type)
> > > {
> > > /************************ My debugging showed that the control came
> > > here *********************/
> > > tree decl = (tree) XOBNEW (&fake_var_decl_obstack, struct
> > > tree_var_decl);
> > > /************************ But did not come here
> > > **********************************************************/
> > > memset (decl, 0, sizeof (struct tree_var_decl));
> > > TREE_SET_CODE (decl, VAR_DECL);
> > > TREE_TYPE (decl) = type;
> > > DECL_UID (decl) = allocate_decl_uid ();
> > > SET_DECL_PT_UID (decl, -1);
> > > layout_decl (decl, 0);
> > > return decl;
> > > }
> > >
> > > The builf_fake_var_decl() function is a gcc function defined in
> > > tree-ssa-structalias.c. To be able to use it in my pass, I removed the
> > > keyword static in its definition.
> > >
> > > I cannot figure out what can possibly cause this error in the XOBNEW
> > > function.
> > >
> > > Please help!!!
> >
> > Don't use build_fake_var_decl, use what 4.6 did, create_tmp_var_raw.
> >
> > Richard.
> >
> >
>
> But 4.6 used get_var_ann() also along with create_tmp_var_raw() which
> has been removed from 4.7.
I would like to clarify my above statement by saying that 4.6 used 2
functions [ie. create_tmp_var_raw() and get_var_ann()] whereas 4.7
used only one function [build_fake_var_decl()] for the same purpose.
Now in 4.7 get_var_ann() is unavailable. So is it safe to use only
create_tmp_var_raw(). In other words, was get_var_ann() a redundant
function in 4.6?
>
> > > Sudakshina Das
