Re: [PATCH] c++: End lifetime of objects in constexpr after destructor call [PR71093]

[Marek Polacek <polacek@redhat.com>]

On Mon, Dec 11, 2023 at 05:00:50PM -0500, Jason Merrill wrote:
> On 12/11/23 14:21, Marek Polacek wrote:
> > On Mon, Dec 11, 2023 at 08:17:22PM +0100, Richard Biener wrote:
> > > 
> > > 
> > > > Am 11.12.2023 um 20:12 schrieb Jason Merrill <jason@redhat.com>:
> > > > Maybe something like this?  Or shall we write out the names like CLOBBER_OBJECT_START, CLOBBER_STORAGE_END, etc?
> > > 
> > > Yeah, the abbreviations look a bit confusing so spelling it out would be better
> > 
> > What about pretty-print, should we keep
> > 
> >    pp_string (pp, "(eol)");
> > 
> > or use the new, more specific description?
> 
> I think we tend toward terseness in pretty-print, though I don't feel
> strongly about it at all.
> 
> But we should handle the other cases as well.

Nice.  I think you're going to have to adjust gcc.dg/pr87052.c because
that checks for "(eol)".

> So, how about:

Obviously I can't approve but, FWIW, it looks good.  I don't see anything
in doc/ that needs updating.  Thanks.

> From e2e535a440a5447b45769e6630cca21d274108f1 Mon Sep 17 00:00:00 2001
> From: Jason Merrill <jason@redhat.com>
> Date: Mon, 11 Dec 2023 11:35:31 -0500
> Subject: [PATCH] tree: add to clobber_kind
> To: gcc-patches@gcc.gnu.org
> 
> In discussion of PR71093 it came up that more clobber_kind options would be
> useful within the C++ front-end.
> 
> gcc/ChangeLog:
> 
> 	* tree-core.h (enum clobber_kind): Rename CLOBBER_EOL to
> 	CLOBBER_STORAGE_END.  Add CLOBBER_STORAGE_BEGIN,
> 	CLOBBER_OBJECT_BEGIN, CLOBBER_OBJECT_END.
> 	* gimple-lower-bitint.cc
> 	* gimple-ssa-warn-access.cc
> 	* gimplify.cc
> 	* tree-inline.cc
> 	* tree-ssa-ccp.cc: Adjust for rename.
> 	* tree-pretty-print.cc: And handle new values.
> ---
>  gcc/tree-core.h               | 13 ++++++++++---
>  gcc/gimple-lower-bitint.cc    |  8 ++++----
>  gcc/gimple-ssa-warn-access.cc |  2 +-
>  gcc/gimplify.cc               |  8 ++++----
>  gcc/tree-inline.cc            |  4 ++--
>  gcc/tree-pretty-print.cc      | 19 +++++++++++++++++--
>  gcc/tree-ssa-ccp.cc           |  2 +-
>  7 files changed, 39 insertions(+), 17 deletions(-)
> 
> diff --git a/gcc/tree-core.h b/gcc/tree-core.h
> index 04c04cf2f37..58aa598f3bb 100644
> --- a/gcc/tree-core.h
> +++ b/gcc/tree-core.h
> @@ -986,12 +986,19 @@ enum annot_expr_kind {
>    annot_expr_kind_last
>  };
>  
> -/* The kind of a TREE_CLOBBER_P CONSTRUCTOR node.  */
> +/* The kind of a TREE_CLOBBER_P CONSTRUCTOR node.  Other than _UNDEF, these are
> +   in roughly sequential order.  */
>  enum clobber_kind {
>    /* Unspecified, this clobber acts as a store of an undefined value.  */
>    CLOBBER_UNDEF,
> -  /* This clobber ends the lifetime of the storage.  */
> -  CLOBBER_EOL,
> +  /* Beginning of storage duration, e.g. malloc.  */
> +  CLOBBER_STORAGE_BEGIN,
> +  /* Beginning of object lifetime, e.g. C++ constructor.  */
> +  CLOBBER_OBJECT_BEGIN,
> +  /* End of object lifetime, e.g. C++ destructor.  */
> +  CLOBBER_OBJECT_END,
> +  /* End of storage duration, e.g. free.  */
> +  CLOBBER_STORAGE_END,
>    CLOBBER_LAST
>  };
>  
> diff --git a/gcc/gimple-lower-bitint.cc b/gcc/gimple-lower-bitint.cc
> index c55c32fb40d..84f92b6e654 100644
> --- a/gcc/gimple-lower-bitint.cc
> +++ b/gcc/gimple-lower-bitint.cc
> @@ -806,7 +806,7 @@ bitint_large_huge::handle_operand (tree op, tree idx)
>  	  && m_after_stmt
>  	  && bitmap_bit_p (m_single_use_names, SSA_NAME_VERSION (op)))
>  	{
> -	  tree clobber = build_clobber (TREE_TYPE (m_vars[p]), CLOBBER_EOL);
> +	  tree clobber = build_clobber (TREE_TYPE (m_vars[p]), CLOBBER_STORAGE_END);
>  	  g = gimple_build_assign (m_vars[p], clobber);
>  	  gimple_stmt_iterator gsi = gsi_for_stmt (m_after_stmt);
>  	  gsi_insert_after (&gsi, g, GSI_SAME_STMT);
> @@ -2063,7 +2063,7 @@ bitint_large_huge::handle_operand_addr (tree op, gimple *stmt,
>        tree ret = build_fold_addr_expr (var);
>        if (!stmt_ends_bb_p (gsi_stmt (m_gsi)))
>  	{
> -	  tree clobber = build_clobber (atype, CLOBBER_EOL);
> +	  tree clobber = build_clobber (atype, CLOBBER_STORAGE_END);
>  	  g = gimple_build_assign (var, clobber);
>  	  gsi_insert_after (&m_gsi, g, GSI_SAME_STMT);
>  	}
> @@ -2100,7 +2100,7 @@ bitint_large_huge::handle_operand_addr (tree op, gimple *stmt,
>  	      ret = build_fold_addr_expr (var);
>  	      if (!stmt_ends_bb_p (gsi_stmt (m_gsi)))
>  		{
> -		  tree clobber = build_clobber (m_limb_type, CLOBBER_EOL);
> +		  tree clobber = build_clobber (m_limb_type, CLOBBER_STORAGE_END);
>  		  g = gimple_build_assign (var, clobber);
>  		  gsi_insert_after (&m_gsi, g, GSI_SAME_STMT);
>  		}
> @@ -3707,7 +3707,7 @@ bitint_large_huge::finish_arith_overflow (tree var, tree obj, tree type,
>      }
>    if (var)
>      {
> -      tree clobber = build_clobber (TREE_TYPE (var), CLOBBER_EOL);
> +      tree clobber = build_clobber (TREE_TYPE (var), CLOBBER_STORAGE_END);
>        g = gimple_build_assign (var, clobber);
>        gsi_insert_after (&m_gsi, g, GSI_SAME_STMT);
>      }
> diff --git a/gcc/gimple-ssa-warn-access.cc b/gcc/gimple-ssa-warn-access.cc
> index 1646bd1be14..f04c2530869 100644
> --- a/gcc/gimple-ssa-warn-access.cc
> +++ b/gcc/gimple-ssa-warn-access.cc
> @@ -4364,7 +4364,7 @@ void
>  pass_waccess::check_stmt (gimple *stmt)
>  {
>    if (m_check_dangling_p
> -      && gimple_clobber_p (stmt, CLOBBER_EOL))
> +      && gimple_clobber_p (stmt, CLOBBER_STORAGE_END))
>      {
>        /* Ignore clobber statements in blocks with exceptional edges.  */
>        basic_block bb = gimple_bb (stmt);
> diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc
> index 342e43a7f25..ffc1882d22a 100644
> --- a/gcc/gimplify.cc
> +++ b/gcc/gimplify.cc
> @@ -1518,7 +1518,7 @@ gimplify_bind_expr (tree *expr_p, gimple_seq *pre_p)
>  		      tmp = build_call_expr_loc (EXPR_LOCATION (*e), tmp, 2, v,
>  						 build_zero_cst (ptr_type_node));
>  		      tsi_link_after (&e, tmp, TSI_SAME_STMT);
> -		      tmp = build_clobber (TREE_TYPE (v), CLOBBER_EOL);
> +		      tmp = build_clobber (TREE_TYPE (v), CLOBBER_STORAGE_END);
>  		      tmp = fold_build2_loc (loc, MODIFY_EXPR, TREE_TYPE (v), v,
>  					     fold_convert (TREE_TYPE (v), tmp));
>  		      ++e;
> @@ -1651,7 +1651,7 @@ gimplify_bind_expr (tree *expr_p, gimple_seq *pre_p)
>  					 build_zero_cst (ptr_type_node));
>  	      gimplify_and_add (tmp, &cleanup);
>  	      gimple *clobber_stmt;
> -	      tmp = build_clobber (TREE_TYPE (v), CLOBBER_EOL);
> +	      tmp = build_clobber (TREE_TYPE (v), CLOBBER_STORAGE_END);
>  	      clobber_stmt = gimple_build_assign (v, tmp);
>  	      gimple_set_location (clobber_stmt, end_locus);
>  	      gimplify_seq_add_stmt (&cleanup, clobber_stmt);
> @@ -1665,7 +1665,7 @@ gimplify_bind_expr (tree *expr_p, gimple_seq *pre_p)
>  	      && !is_gimple_reg (t)
>  	      && flag_stack_reuse != SR_NONE)
>  	    {
> -	      tree clobber = build_clobber (TREE_TYPE (t), CLOBBER_EOL);
> +	      tree clobber = build_clobber (TREE_TYPE (t), CLOBBER_STORAGE_END);
>  	      gimple *clobber_stmt;
>  	      clobber_stmt = gimple_build_assign (t, clobber);
>  	      gimple_set_location (clobber_stmt, end_locus);
> @@ -7417,7 +7417,7 @@ gimplify_target_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p)
>  	{
>  	  if (flag_stack_reuse == SR_ALL)
>  	    {
> -	      tree clobber = build_clobber (TREE_TYPE (temp), CLOBBER_EOL);
> +	      tree clobber = build_clobber (TREE_TYPE (temp), CLOBBER_STORAGE_END);
>  	      clobber = build2 (MODIFY_EXPR, TREE_TYPE (temp), temp, clobber);
>  	      gimple_push_cleanup (temp, clobber, false, pre_p, true);
>  	    }
> diff --git a/gcc/tree-inline.cc b/gcc/tree-inline.cc
> index a4fc839a22d..cca3227fa89 100644
> --- a/gcc/tree-inline.cc
> +++ b/gcc/tree-inline.cc
> @@ -5136,7 +5136,7 @@ expand_call_inline (basic_block bb, gimple *stmt, copy_body_data *id,
>  	      && !is_gimple_reg (*varp)
>  	      && !(id->debug_map && id->debug_map->get (p)))
>  	    {
> -	      tree clobber = build_clobber (TREE_TYPE (*varp), CLOBBER_EOL);
> +	      tree clobber = build_clobber (TREE_TYPE (*varp), CLOBBER_STORAGE_END);
>  	      gimple *clobber_stmt;
>  	      clobber_stmt = gimple_build_assign (*varp, clobber);
>  	      gimple_set_location (clobber_stmt, gimple_location (stmt));
> @@ -5208,7 +5208,7 @@ expand_call_inline (basic_block bb, gimple *stmt, copy_body_data *id,
>  	  && !is_gimple_reg (id->retvar)
>  	  && !stmt_ends_bb_p (stmt))
>  	{
> -	  tree clobber = build_clobber (TREE_TYPE (id->retvar), CLOBBER_EOL);
> +	  tree clobber = build_clobber (TREE_TYPE (id->retvar), CLOBBER_STORAGE_END);
>  	  gimple *clobber_stmt;
>  	  clobber_stmt = gimple_build_assign (id->retvar, clobber);
>  	  gimple_set_location (clobber_stmt, gimple_location (old_stmt));
> diff --git a/gcc/tree-pretty-print.cc b/gcc/tree-pretty-print.cc
> index 0dabb6d1580..cab99f9dfb6 100644
> --- a/gcc/tree-pretty-print.cc
> +++ b/gcc/tree-pretty-print.cc
> @@ -2624,8 +2624,23 @@ dump_generic_node (pretty_printer *pp, tree node, int spc, dump_flags_t flags,
>  	if (TREE_CLOBBER_P (node))
>  	  {
>  	    pp_string (pp, "CLOBBER");
> -	    if (CLOBBER_KIND (node) == CLOBBER_EOL)
> -	      pp_string (pp, "(eol)");
> +	    switch (CLOBBER_KIND (node))
> +	      {
> +	      case CLOBBER_STORAGE_BEGIN:
> +		pp_string (pp, "(bos)");
> +		break;
> +	      case CLOBBER_STORAGE_END:
> +		pp_string (pp, "(eos)");
> +		break;
> +	      case CLOBBER_OBJECT_BEGIN:
> +		pp_string (pp, "(bob)");
> +		break;
> +	      case CLOBBER_OBJECT_END:
> +		pp_string (pp, "(eob)");
> +		break;
> +	      default:
> +		break;
> +	      }
>  	  }
>  	else if (TREE_CODE (TREE_TYPE (node)) == RECORD_TYPE
>  		 || TREE_CODE (TREE_TYPE (node)) == UNION_TYPE)
> diff --git a/gcc/tree-ssa-ccp.cc b/gcc/tree-ssa-ccp.cc
> index ddcbaaaa417..fab2a9b248a 100644
> --- a/gcc/tree-ssa-ccp.cc
> +++ b/gcc/tree-ssa-ccp.cc
> @@ -2525,7 +2525,7 @@ insert_clobber_before_stack_restore (tree saved_val, tree var,
>    FOR_EACH_IMM_USE_STMT (stmt, iter, saved_val)
>      if (gimple_call_builtin_p (stmt, BUILT_IN_STACK_RESTORE))
>        {
> -	clobber = build_clobber (TREE_TYPE (var), CLOBBER_EOL);
> +	clobber = build_clobber (TREE_TYPE (var), CLOBBER_STORAGE_END);
>  	clobber_stmt = gimple_build_assign (var, clobber);
>  
>  	i = gsi_for_stmt (stmt);
> -- 
> 2.39.3
> 


Marek