RE: PING: Fwd: Re: [patch] implement Cilk Plus simd loops on trunk

["Iyer, Balaji V" <balaji dot v dot iyer at intel dot com>]

> -----Original Message-----
> From: gcc-patches-owner@gcc.gnu.org [mailto:gcc-patches-
> owner@gcc.gnu.org] On Behalf Of Aldy Hernandez
> Sent: Wednesday, October 16, 2013 1:49 PM
> To: Jason Merrill
> Cc: Richard Henderson; gcc-patches; Iyer, Balaji V
> Subject: Re: PING: Fwd: Re: [patch] implement Cilk Plus simd loops on trunk
> 
> On 10/02/13 16:53, Jason Merrill wrote:
> > On 08/27/2013 04:03 PM, Aldy Hernandez wrote:
> 
> >
> >> +          else if (!TREE_TYPE (e) || !TREE_CONSTANT (e)
> >> +               || !INTEGRAL_TYPE_P (TREE_TYPE (e)))
> >> +        cp_parser_error (parser,
> >> +                 "step size must be an integer constant");
> >
> > Can't the step size be a value-dependent expression like a template
> > non-type parameter?
> 
> [Balaji, this is for the linear clause that is either linear(var) or linear(var : step)].
> 
> Jason, I'm not sure.  The standard says:
> 
> 	"The conditional-expression in a simd-linear-step shall either
> 	satisfy the requirements of an integer constant expression, or
> 	be a reference to a variable with integer type."
> 
> I take this to mean, an integral expression or a plain old variable.  Is this the
> case, Balaji?
> 
Yup.


> Jason, are you asking about the validity of something like this:
> 
> int *p;
> 
> template <int argoop>
> void foobar(int a)
> {
>    int j = 123;
> #pragma simd linear(j : argoop)
>    for (int i=0; i < a; ++i)
>      p[i] = argoop;
> }
> 
> void funky()
> {
>    foobar <69> (1000);
> }
> 
> If this is what you're asking, and the above standardeese allows it, then we have
> a problem, because the code parsing the "j" in the linear clause uses
> cp_parser_id_expression() which gets horrendously confused with the colon,
> expecting a '::'.  For that matter, even doing this causes problems:
> 

In parser structure, there is a variable that called colon_corrects_to_scope_p. Set that to false right before searching for a colon. That should fix this looking for :: issue.

> 	int j = 123, k = 456;
> 	#pragma simd linear (j : k)
> 	...
> 
> Is this what you were asking about?  If so, then perhaps something besides
> cp_parser_id_expression is in order, for the sake of the template argument or
> just a plain variable.
> 

Thanks,

Balaji V. Iyer.


> Aldy