On Fri, Jan 25, 2013 at 9:27 PM, Richard Biener
<richard.guent...@gmail.com> wrote:
> On Fri, Jan 25, 2013 at 3:57 PM, Sudakshina Das
> <sudakshina1...@gmail.com> wrote:
>> On Fri, Jan 25, 2013 at 8:02 PM, Richard Biener
>> <richard.guent...@gmail.com> wrote:
>>> On Fri, Jan 25, 2013 at 3:05 PM, Sudakshina Das
>>> <sudakshina1...@gmail.com> wrote:
>>>> 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?
>>>
>>> The whole function is very special for tree-ssa-structalias.c. I have no
>>> idea
>>> what your pass does, but unless it closely resembles tree-ssa-structalias.c
>>> and shares its internal data structures you shouldn't blindly copy over what
>>> tree-ssa-structalias.c does (well, at least not without understanding what
>>> you
>>> are doing).
>>>
>>> What do you think you are doing with the copy of that code?
>>>
>>> Richard.
>>>
>>>>
>>>>>
>>
>>
>> The copy of the above code is from function create_function_info_for()
>> in tree-ssa-structalias.c which is used to create variables for a
>> function in its tree. In the pass there is a similar function named
>> cs_create_func_info_for() used for the same purpose, except it does
>> not create variables for all the cases. In other words some portions
>> from the original function is omitted. Also the data structure
>> varinfo_t is modified a bit to suite the pass and renamed as
>> csvarinfo_t. I have copied the function from my pass below,
>> highlighting the difference from the original function using comments.
>
> Well, then you can literally copy the original function. Just make sure
> to also copy and initialize and free the obstack it uses.
>
Thank you!!!!! The initializing and freeing obstack was the problem.
So with that and after removing a few more glitches the pass is now
running!!!
>> /* Creation function node for DECL, using NAME, and return the index
>> of the variable we've created for the function. */
>> static csvarinfo_t
>> cs_create_func_info_for (tree decl, const char *name)
>> {
>> csvarinfo_t vi, prev_vi;
>> tree arg;
>> unsigned int i;
>> bool is_varargs = false;
>> unsigned int num_args = count_num_arguments (decl, &is_varargs);
>>
>> /* Create the variable info. */
>> vi = cs_new_var_info (decl, name);
>> vi->offset = 0;
>> vi->size = 1;
>> vi->fullsize = num_args + 1;
>> vi->may_have_pointers = false;
>> if (is_varargs)
>> vi->fullsize = ~0;
>> cs_insert_vi_for_tree (vi->decl, vi);
>>
>> prev_vi = vi
>>
>> /************ There were portions in original code with the
>> following comments: **************
>>
>> 1. Create a variable for things the function clobbers and one
>> for things the function uses.
>>
>> 2. And one for the static chain.
>>
>> 3. Create a variable for the return var.
>>
>>
>> *******************************************************************************************************/
>>
>> /* Set up variables for each argument. */
>> arg = DECL_ARGUMENTS (decl);
>> for (i = 1; i < num_args + 1; i++) {
>> csvarinfo_t argvi;
>> tree argdecl = decl;
>>
>> if (arg)
>> argdecl = arg;
>>
>> argvi = cs_new_var_info (argdecl, alias_get_name (argdecl));
>> argvi->offset = i;
>> argvi->size = 1;
>> argvi->is_full_var = true;
>> argvi->fullsize = vi->fullsize;
>> if (arg)
>> argvi->may_have_pointers = true;
>> gcc_assert (prev_vi->offset < argvi->offset);
>> prev_vi->next = argvi;
>> prev_vi = argvi;
>> if (arg) {
>> cs_insert_vi_for_tree (arg, argvi);
>> arg = DECL_CHAIN (arg);
>> }
>> }
>>
>> /* Add one representative for all further args. */
>> if (is_varargs) {
>> csvarinfo_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. */
>> decl = create_tmp_var_raw (ptr_type_node, name);
>> get_var_ann (decl);
>>
>> argvi = cs_new_var_info (decl, newname);
>> argvi->offset = 1 + 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;
>> }
>>
>>
>> Sudakshina Das
