Re: [PATCH, C++] Wrap OpenACC wait in EXPR_STMT

[Chung-Lin Tang <cltang at codesourcery dot com>]

On 2015/12/3 4:59 PM, Thomas Schwinge wrote:
> Hi!
> 
> On Thu, 03 Dec 2015 09:51:31 +0100, I wrote:
>> On Mon, 23 Nov 2015 21:15:00 +0800, Chung-Lin Tang <cltang@codesourcery.com> wrote:
>>> The OpenACC wait directive is represented as a call to the runtime
>>> function "GOACC_wait" instead of a tree code.  I am seeing when
>>> '#pragma acc wait' is using inside a template function, the CALL_EXPR
>>> to GOACC_wait is being silently ignored/removed during tsubst_expr().
>>
>> Uh.
>>
>>> I think the correct way to organize this is that the call should be inside
>>> an EXPR_STMT, so here's a patch to do that; basically remove the
>>> add_stmt() call from the shared c_finish_oacc_wait() code, and add
>>> add_stmt()/finish_expr_stmt() in the corresponding C/C++ parts.
>>>
>>> Tested with no regressions on trunk, okay to commit?
>>
>>> --- c-family/c-omp.c	(revision 230703)
>>> +++ c-family/c-omp.c	(working copy)
>>> @@ -63,7 +63,6 @@ c_finish_oacc_wait (location_t loc, tree parms, tr
>>>      }
>>>  
>>>    stmt = build_call_expr_loc_vec (loc, stmt, args);
>>> -  add_stmt (stmt);
>>>  
>>>    vec_free (args);
>> |  
>> |    return stmt;
>> |  }
>>
>> I see in gcc/c/c-omp.c that several other c_finish_omp_* functions that
>> build builtin calls instead of tree nodes, do similar things like
>> c_finish_oacc_wait; I'd like to understand why it's -- presumably -- not
>> a problem for these: c_finish_omp_barrier, c_finish_omp_taskwait,
>> c_finish_omp_taskyield, c_finish_omp_flush?  (Jakub?)
> 
> Oh wait, it looks like the C++ front end is not actually using the
> functions defined in the C/C++-shared gcc/c-family/c-omp.c, but has its
> own implementations in gcc/cp/semantics.c, without "c_" prefixes?  In
> addition to finish_expr_stmt calls, I see it's also using
> finish_call_expr instead of build_call_expr_loc/build_call_expr_loc_vec.
> So I guess we'll want to model this the same way for OpenACC support
> functions, and then (later) we should clean this up, to move the
> C-specific code from gcc/c-family/c-omp.c into the C front end?  (Jakub?)

I see most OpenACC/OpenMP constructs are represented by special statement codes,
so they should be a different case. I so far only see the OpenACC wait directive
being represented as a CALL_EXPR (maybe there are others, haven't exhaustively searched).

Chung-Lin