[GSoC] replacing op in c_expr

[Prathamesh Kulkarni]

On Mon, Aug 4, 2014 at 2:13 PM, Richard Biener
<richard.guenther@gmail.com> wrote:
> On Sun, Aug 3, 2014 at 6:58 PM, Prathamesh Kulkarni
> <bilbotheelffriend@gmail.com> wrote:
>> On Tue, Jul 29, 2014 at 4:29 PM, Richard Biener
>> <richard.guenther@gmail.com> wrote:
>>> On Mon, Jul 28, 2014 at 10:02 PM, Prathamesh Kulkarni
>>> <bilbotheelffriend@gmail.com> wrote:
>>>> I am having few issues replacing op in c_expr.
>>>> I thought of following possibilities:
>>>>
>>>> a) create a new vec<cpp_token> vector new_code.
>>>> for each token in code
>>>>   {
>>>>     if token.type is not CPP_NAME
>>>>       new_code.safe_push (token);
>>>>     else
>>>>      {
>>>>         cpp_token new_token =
>>>>             ??? create new token of type CPP_NAME
>>>>                   with contents as name of operator ???
>>>>      }
>>>>   }
>>>>
>>>> I tried to go this way, but am stuck with creating a new token type.
>>>> i started by:
>>>> cpp_token new_token = token;  // get same attrs as token.
>>>> CPP_HASHNODE (new_token.val.node.node)->ident.str = name of operator.
>>>> CPP_HASHNODE (new_token.val.node.node)->ident.len = len of operator name.
>>>> name of operator is obtained from opers[i] in parse_for.
>>>>
>>>> however this does not work because I guess
>>>>  new_token = token, shallow copies
>>>> the token (default assignment operator, i didn't find an overloaded version).
>>>>
>>>> b) create new struct c_expr_elem and use
>>>> vec<c_expr_elem> code, instead of vec<cpp_token> code;
>>>>
>>>> sth like:
>>>> struct c_expr_elem
>>>> {
>>>>    enum c_expr_elem_type { ID, TOKEN };
>>>>    enum c_expr_elem_type type;
>>>>
>>>>    union {
>>>>      cpp_token token;
>>>>      const char *id;
>>>>    };
>>>> };
>>>>
>>>> while replacing op, compare token with op, and if it matches,
>>>> create a new c_expr_elem with type = ID, and id = name of operator.
>>>> This shall probably work, but shall require many changes to other parts
>>>> since we change c_expr::code.
>>>>
>>>> I would like to hear any other suggestions.
>>>
>>> Together with the vector of tokens recorded at parse_c_expr time
>>> record a vector of token mappings (op -> plus, op2 -> ...) and do
>>> the replacement at code-generation time where we also special-case
>>> captures.
>>>
>>> Yeah, it's a but unfortunate that c_expr parsing is done the way it
>>> is done....
>> Thanks. I guess we would require a multi-map for this since there can
>> be many operators
>> (op -> [plus, minus], op2 -> [negate]) ?
>
> Well, it would be enough to attach the mapping to c_expr()s after the
> AST lowering when there is at most one?  Because obviously
> code-generation cannot know which to replace.
>
>> Unfortunately, I somehow seem to have missed your response and ended up with a
>> hackish way of doing it, although it works. I will soon change that to
>> use token mappings.
>>
>> I mostly followed b), except i made it sub-class of cpp_token, so the
>> other code using c_expr::code
>> (outline_c_expr, c_expr::gen_transform) did not require changes except
>> for special-casing op.
>
> Indeed not too ugly.  Still at the point where you replace in the for()
> processing
>
> -             operand *result_op = replace_id (s->result, user_id, opers[i]);
> +
> +             operand *result_op;
> +             if (is_a<c_expr *> (s->result))
> +               result_op = replace_op_in_c_expr (s->result, user_id, opers[i]);
> +             else
> +               result_op = replace_id (s->result, user_id, opers[i]);
> +
> +
>
> it should be "easy" to attach a replacemet vector/map to the c_expr
> and use that duing code-generation.
>
> Note that sub-expressions can also be c_exprs, thus
>
> (match-and-simplify
>    (....)
>    (plus { ... } @2))
>
> I don't think your patch covers that.  That is, you should add
> c_expr handing to replace_id instead.
Thanks, this patch covers that case.
For now, I have still kept the old way, since the change was one-liner.
I will change it after I am done with conditional convert

* genmatch.c (c_expr::elem): New struct.
     (c_expr::code): Change type to vec<c_expr::elem>.
     (replace_op_in_c_expr): New function.
     (replace_id): Call replace_op_in_c_expr.
     (c_expr::gen_transform): Adjust to changes in c_expr.
     (outline_c_expr): Likewise.
     (parse_c_expr): Likewise.
     (parse_for): Call replace_op_in_c_expr.

Thanks,
Prathamesh
>
> Richard.
>
>> * genmatch.c (c_expr::elem): New struct.
>>      (c_expr::code): Change type to vec<c_expr::elem>.
>>      (replace_op_in_c_expr): New function.
>>      (c_expr::gen_transform): Adjust to changes in c_expr.
>>      (outline_c_expr): Likewise.
>>      (parse_c_expr): Likewise.
>>      (parse_for): Call replace_op_in_c_expr.
>>
>> Thanks,
>> Prathamesh
>>
>>>
>>> Richard.
>>>
>>>> Thanks,
>>>> Prathamesh.
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