Re: maybe_fold_stmt (was: [gomp4] #pragma omp target* fixes)

[Thomas Schwinge <thomas at codesourcery dot com>]

Hi!

Ping.

On Fri, 13 Dec 2013 11:13:03 +0100, I wrote:
> On Thu, 5 Sep 2013 18:11:05 +0200, Jakub Jelinek <jakub@redhat.com> wrote:
> > 4) the reference testcase showed a problem with fold_stmt calls
> > we do very early, during gimplification, because for TREE_READONLY
> > vars with DECL_INITIAL fold_stmt can replace the uses of the var with
> > its initializer, but as the gimplifier isn't aware of it, we wouldn't remap
> > that, or worse there could be explicit remapping of it via array section,
> > but one that the compiler doesn't see, and if that is smaller than
> > the whole array size, that would result in runtime error.  So, after
> > some talk with richi on IRC, I've decided to just not fold_stmt
> > inside of target constructs during gimplification and defer it until
> > omplower.
> 
> > 	* gimplify.c (gimplify_call_expr): Don't call fold_stmt
> > 	inside of #pragma omp target construct.
> > 	(gimplify_modify_expr): Likewise.
> > 	* omp-low.c
> > 	(lower_omp): Call fold_stmt on all stmts inside of
> > 	#pragma omp target construct.
> 
> > --- gcc/gimplify.c.jj	2013-09-05 09:19:03.000000000 +0200
> > +++ gcc/gimplify.c	2013-09-05 14:45:48.632720617 +0200
> > @@ -2704,7 +2704,14 @@ gimplify_call_expr (tree *expr_p, gimple
> >        notice_special_calls (call);
> >        gimplify_seq_add_stmt (pre_p, call);
> >        gsi = gsi_last (*pre_p);
> > -      fold_stmt (&gsi);
> > +      /* Don't fold stmts inside of target construct.  We'll do it
> > +	 during omplower pass instead.  */
> > +      struct gimplify_omp_ctx *ctx;
> > +      for (ctx = gimplify_omp_ctxp; ctx; ctx = ctx->outer_context)
> > +	if (ctx->region_type == ORT_TARGET)
> > +	  break;
> > +      if (ctx == NULL)
> > +	fold_stmt (&gsi);
> >        *expr_p = NULL_TREE;
> >      }
> >    else
> > @@ -4961,7 +4968,14 @@ gimplify_modify_expr (tree *expr_p, gimp
> >  
> >    gimplify_seq_add_stmt (pre_p, assign);
> >    gsi = gsi_last (*pre_p);
> > -  fold_stmt (&gsi);
> > +  /* Don't fold stmts inside of target construct.  We'll do it
> > +     during omplower pass instead.  */
> > +  struct gimplify_omp_ctx *ctx;
> > +  for (ctx = gimplify_omp_ctxp; ctx; ctx = ctx->outer_context)
> > +    if (ctx->region_type == ORT_TARGET)
> > +      break;
> > +  if (ctx == NULL)
> > +    fold_stmt (&gsi);
> >  
> >    if (want_value)
> >      {
> > --- gcc/omp-low.c.jj	2013-09-05 09:19:03.000000000 +0200
> > +++ gcc/omp-low.c	2013-09-05 17:11:14.693638660 +0200
> > @@ -9673,6 +9685,12 @@ lower_omp (gimple_seq *body, omp_context
> >    gimple_stmt_iterator gsi;
> >    for (gsi = gsi_start (*body); !gsi_end_p (gsi); gsi_next (&gsi))
> >      lower_omp_1 (&gsi, ctx);
> > +  /* Inside target region we haven't called fold_stmt during gimplification,
> > +     because it can break code by adding decl references that weren't in the
> > +     source.  Call fold_stmt now.  */
> > +  if (target_nesting_level)
> > +    for (gsi = gsi_start (*body); !gsi_end_p (gsi); gsi_next (&gsi))
> > +      fold_stmt (&gsi);
> >    input_location = saved_location;
> >  }
> 
> OK to commit to trunk the following patch?
> 
> commit 6ff10eb51ea39a25e53e0369626559be208bb16e
> Author: Thomas Schwinge <thomas@codesourcery.com>
> Date:   Mon Oct 21 16:37:41 2013 +0200
> 
>     Refactor common code into new maybe_fold_stmt function.
>     
>     	gcc/
>     	* gimplify.c (gimplify_call_expr, gimplify_modify_expr): Move
>     	common code...
>     	(maybe_fold_stmt): ... into this new function.
>     	* omp-low.c (lower_omp): Update comment.
> 
> diff --git gcc/gimplify.c gcc/gimplify.c
> index 1ca847a..7203456 100644
> --- gcc/gimplify.c
> +++ gcc/gimplify.c
> @@ -2184,6 +2184,23 @@ gimplify_arg (tree *arg_p, gimple_seq *pre_p, location_t call_location)
>    return gimplify_expr (arg_p, pre_p, NULL, test, fb);
>  }
>  
> +/* Don't fold STMT inside ORT_TARGET, because it can break code by adding decl
> +   references that weren't in the source.  We'll do it during omplower pass
> +   instead.  */
> +
> +static bool
> +maybe_fold_stmt (gimple_stmt_iterator *gsi)
> +{
> +  bool changed = false;
> +  struct gimplify_omp_ctx *ctx;
> +  for (ctx = gimplify_omp_ctxp; ctx; ctx = ctx->outer_context)
> +    if (ctx->region_type == ORT_TARGET)
> +      break;
> +  if (ctx == NULL)
> +    changed = fold_stmt (gsi);
> +  return changed;
> +}
> +
>  /* Gimplify the CALL_EXPR node *EXPR_P into the GIMPLE sequence PRE_P.
>     WANT_VALUE is true if the result of the call is desired.  */
>  
> @@ -2417,14 +2434,7 @@ gimplify_call_expr (tree *expr_p, gimple_seq *pre_p, bool want_value)
>        notice_special_calls (call);
>        gimplify_seq_add_stmt (pre_p, call);
>        gsi = gsi_last (*pre_p);
> -      /* Don't fold stmts inside of target construct.  We'll do it
> -	 during omplower pass instead.  */
> -      struct gimplify_omp_ctx *ctx;
> -      for (ctx = gimplify_omp_ctxp; ctx; ctx = ctx->outer_context)
> -	if (ctx->region_type == ORT_TARGET)
> -	  break;
> -      if (ctx == NULL)
> -	fold_stmt (&gsi);
> +      maybe_fold_stmt (&gsi);
>        *expr_p = NULL_TREE;
>      }
>    else
> @@ -4572,14 +4582,7 @@ gimplify_modify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
>  
>    gimplify_seq_add_stmt (pre_p, assign);
>    gsi = gsi_last (*pre_p);
> -  /* Don't fold stmts inside of target construct.  We'll do it
> -     during omplower pass instead.  */
> -  struct gimplify_omp_ctx *ctx;
> -  for (ctx = gimplify_omp_ctxp; ctx; ctx = ctx->outer_context)
> -    if (ctx->region_type == ORT_TARGET)
> -      break;
> -  if (ctx == NULL)
> -    fold_stmt (&gsi);
> +  maybe_fold_stmt (&gsi);
>  
>    if (want_value)
>      {
> diff --git gcc/omp-low.c gcc/omp-low.c
> index 05fca40..1222df6 100644
> --- gcc/omp-low.c
> +++ gcc/omp-low.c
> @@ -10110,9 +10110,8 @@ lower_omp (gimple_seq *body, omp_context *ctx)
>    gimple_stmt_iterator gsi;
>    for (gsi = gsi_start (*body); !gsi_end_p (gsi); gsi_next (&gsi))
>      lower_omp_1 (&gsi, ctx);
> -  /* Inside target region we haven't called fold_stmt during gimplification,
> -     because it can break code by adding decl references that weren't in the
> -     source.  Call fold_stmt now.  */
> +  /* During gimplification, we haven't called fold_stmt inside ORT_TARGET
> +     (gimplify.c:maybe_fold_stmt); call it now.  */
>    if (target_nesting_level)
>      for (gsi = gsi_start (*body); !gsi_end_p (gsi); gsi_next (&gsi))
>        fold_stmt (&gsi);


GrÃÃe,
 Thomas

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