Re: [patch] [gsoc] [gimplefe] GIMPLE FE Project

[Richard Biener <richard dot guenther at gmail dot com>]

On Thu, Oct 6, 2016 at 1:28 AM, Joseph Myers <joseph@codesourcery.com> wrote:
> On Fri, 26 Aug 2016, Prasad Ghangal wrote:
>
>> >> Thanks for your feedback. I had missed removing some unwanted code
>> >> while code cleanup. I have updated the patch.
>> >> I am not sure if we should move all gimple parsing related functions
>> >> to the new file (?)
>> >
>> > I think it might be good to make the parts of the C parser you use more
>> > obvious (you'd need to export functions like c_parser_next_token_is).
>> >
>> > The easiest way to "force" that is to put all of the gimple parsing into
>> > a separate file.
>> >
>> > Note I am not so much concerned about this at the moment, the parts to
>> > improve would be avoiding more of the C-isms like convert_lvalue_to_rvalue,
>> > handling of SIZEOF_EXPR and other stuff that looks redundant (you've
>> > probably copied this from the C parsing routines and refactored it).
>> > Also the GIMPLE parser shouldn't do any warnings (just spotted
>> > a call to warn_for_memset).
>> >
>> PFA updated patch (successfully bootstrapped and tested on
>> x86_64-pc-linux-gnu). I have removed unnecessary code. On side I am
>> also trying to move gimple parser related functions to new file. But
>> for it we also have to move structs like c_token, c_parser. Won't it
>> disturb the c-parser code structure ?

Thanks Joseph for the review.  Prasad - do you have time in the next few weeks
to continue working on this?  I'm currently trying to move what is on the github
branch to a branch on git://gcc.gnu.org/git/gcc.git to make it mergeable
(looks like the github repo isn't a clone of the gcc git mirror on github?).

Thanks,
Richard.

> I think the GIMPLE parsing should go in a separate file (meaning exporting
> relevant types and function declarations in a new c-parser.h).
>
>> diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
>> index a5358ed..3c4d2cc 100644
>> --- a/gcc/c-family/c.opt
>> +++ b/gcc/c-family/c.opt
>> @@ -200,6 +200,10 @@ F
>>  Driver C ObjC C++ ObjC++ Joined Separate MissingArgError(missing path after %qs)
>>  -F <dir>     Add <dir> to the end of the main framework include path.
>>
>> +fgimple
>> +C Var(flag_gimple) Init(0)
>> +Enable parsing GIMPLE
>
> You should get a test failure here from the missing "." at the end of the
> help text.
>
> Of course the option also needs documenting in invoke.texi.
>
>> @@ -1659,6 +1695,9 @@ c_parser_declaration_or_fndef (c_parser *parser, bool fndef_ok,
>>    tree all_prefix_attrs;
>>    bool diagnosed_no_specs = false;
>>    location_t here = c_parser_peek_token (parser)->location;
>> +  bool gimple_body_p = false;
>> +  opt_pass *pass = NULL;
>> +  bool startwith_p = false;
>
> The comment above the function needs updating to document the new syntax.
>
>> +static void
>> +c_parser_gimple_expression (c_parser *parser, gimple_seq *seq)
>> +{
>> +  struct c_expr lhs, rhs;
>> +  gimple *assign = NULL;
>> +  enum tree_code subcode = NOP_EXPR;
>> +  location_t loc;
>> +  tree arg = NULL_TREE;
>> +  auto_vec<tree> vargs;
>> +
>> +  lhs = c_parser_gimple_unary_expression (parser);
>> +  rhs.value = error_mark_node;
>> +
>> +  if (c_parser_next_token_is (parser, CPP_EQ))
>> +    {
>> +      c_parser_consume_token (parser);
>> +    }
>
> Redundant braces around a single statement.  Also, this looks wrong, in
> that it seems like you'd accept a random '=' token at this point
> regardless of what follows and whether '=' makes sense in this context.
> You need to have proper cases: if '=' parse what makes sense after '=',
> otherwise parse what makes sense without '=', so that invalid syntax is
> not accepted.
>
>> +  if (c_parser_next_token_is (parser, CPP_AND) ||
>> +      c_parser_next_token_is (parser, CPP_MULT) ||
>> +      c_parser_next_token_is (parser, CPP_PLUS) ||
>> +      c_parser_next_token_is (parser, CPP_MINUS) ||
>> +      c_parser_next_token_is (parser, CPP_COMPL) ||
>> +      c_parser_next_token_is (parser, CPP_NOT))
>
> Operators go at the start of a continuation line, not at the end of the
> line.
>
>> +      if (!c_parser_require (parser, CPP_OPEN_PAREN, "expected %<(%>"))
>> +     {
>> +       return;
>> +     }
>
> Please generally review the patch for redundant braces and remove them.
>
>> +  /* ssa token string.  */
>> +  const char *ssa_token = IDENTIFIER_POINTER (c_parser_peek_token (parser)->value);
>> +  token = new char [strlen (ssa_token)];
>> +  strcpy (token, ssa_token);
>
> That looks like a buffer overrun.  To copy a string ssa_token, you need
> strlen (ssa_token) + 1 bytes of space.
>
>> +  /* seperate var name and version.  */
>
> Uppercase letters at start of comments, throughout the patch (and it
> should be "Separate", with 'a' not 'e').
>
> --
> Joseph S. Myers
> joseph@codesourcery.com