Re: [PATCH v2] c++: Fix further protected_set_expr_location related -fcompare-debug issues [PR94441]

[Jason Merrill <jason@redhat.com>]

On 4/3/20 4:12 PM, Jakub Jelinek wrote:
> On Fri, Apr 03, 2020 at 03:02:58PM -0400, Jason Merrill via Gcc-patches wrote:
>>> Or do we want a further wrapper, perhaps C++ FE only, that would do this
>>> protected_set_expr_location_if_unset (stmt, locus)?
>>
>> That sounds good to me.
> 
> So like this if it passes bootstrap/regtest?

OK.

> 2020-04-03  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR debug/94441
> 	* tree-iterator.h (expr_single): Declare.
> 	* tree-iterator.c (expr_single): New function.
> 	* tree.h (protected_set_expr_location_if_unset): Declare.
> 	* tree.c (protected_set_expr_location): Use expr_single.
> 	(protected_set_expr_location_if_unset): New function.
> 
> 	* parser.c (cp_parser_omp_for_loop): Use
> 	protected_set_expr_location_if_unset.
> 	* cp-gimplify.c (genericize_if_stmt, genericize_cp_loop): Likewise.
> 
> 	* g++.dg/opt/pr94441.C: New test.
> 
> --- gcc/tree-iterator.h.jj	2020-04-02 12:53:41.556232418 +0200
> +++ gcc/tree-iterator.h	2020-04-03 21:07:01.335933695 +0200
> @@ -119,5 +119,6 @@ extern void append_to_statement_list (tr
>   extern void append_to_statement_list_force (tree, tree *);
>   extern tree expr_first (tree);
>   extern tree expr_last (tree);
> +extern tree expr_single (tree);
>   
>   #endif /* GCC_TREE_ITERATOR_H  */
> --- gcc/tree-iterator.c.jj	2020-04-02 12:53:41.555232434 +0200
> +++ gcc/tree-iterator.c	2020-04-03 21:07:01.335933695 +0200
> @@ -354,4 +354,45 @@ expr_last (tree expr)
>     return expr;
>   }
>   
> +/* If EXPR is a STATEMENT_LIST containing just DEBUG_BEGIN_STMTs and
> +   a single other stmt, return that other stmt (recursively).
> +   If it is a STATEMENT_LIST containing no non-DEBUG_BEGIN_STMTs or
> +   multiple, return NULL_TREE.
> +   Otherwise return EXPR.  */
> +
> +tree
> +expr_single (tree expr)
> +{
> +  if (expr == NULL_TREE)
> +    return expr;
> +
> +  if (TREE_CODE (expr) == STATEMENT_LIST)
> +    {
> +      /* With -gstatement-frontiers we could have a STATEMENT_LIST with
> +	 DEBUG_BEGIN_STMT(s) and only a single other stmt, which with
> +	 -g wouldn't be present and we'd have that single other stmt
> +	 directly instead.  */
> +      struct tree_statement_list_node *n = STATEMENT_LIST_HEAD (expr);
> +      if (!n)
> +	return NULL_TREE;
> +      while (TREE_CODE (n->stmt) == DEBUG_BEGIN_STMT)
> +	{
> +	  n = n->next;
> +	  if (!n)
> +	    return NULL_TREE;
> +	}
> +      expr = n->stmt;
> +      do
> +	{
> +	  n = n->next;
> +	  if (!n)
> +	    return expr_single (expr);
> +	}
> +      while (TREE_CODE (n->stmt) == DEBUG_BEGIN_STMT);
> +      return NULL_TREE;
> +    }
> +
> +  return expr;
> +}
> +
>   #include "gt-tree-iterator.h"
> --- gcc/tree.h.jj	2020-01-31 19:18:02.643900799 +0100
> +++ gcc/tree.h	2020-04-03 21:09:26.134805791 +0200
> @@ -1203,6 +1203,7 @@ get_expr_source_range (tree expr)
>   }
>   
>   extern void protected_set_expr_location (tree, location_t);
> +extern void protected_set_expr_location_if_unset (tree, location_t);
>   
>   extern tree maybe_wrap_with_location (tree, location_t);
>   
> --- gcc/tree.c.jj	2020-04-03 15:41:34.442645256 +0200
> +++ gcc/tree.c	2020-04-03 21:08:57.422227740 +0200
> @@ -5148,33 +5148,23 @@ protected_set_expr_location (tree t, loc
>       SET_EXPR_LOCATION (t, loc);
>     else if (t && TREE_CODE (t) == STATEMENT_LIST)
>       {
> -      /* With -gstatement-frontiers we could have a STATEMENT_LIST with
> -	 DEBUG_BEGIN_STMT(s) and only a single other stmt, which with
> -	 -g wouldn't be present and we'd have that single other stmt
> -	 directly instead.  */
> -      struct tree_statement_list_node *n = STATEMENT_LIST_HEAD (t);
> -      if (!n)
> -	return;
> -      while (TREE_CODE (n->stmt) == DEBUG_BEGIN_STMT)
> -	{
> -	  n = n->next;
> -	  if (!n)
> -	    return;
> -	}
> -      tree t2 = n->stmt;
> -      do
> -	{
> -	  n = n->next;
> -	  if (!n)
> -	    {
> -	      protected_set_expr_location (t2, loc);
> -	      return;
> -	    }
> -	}
> -      while (TREE_CODE (n->stmt) == DEBUG_BEGIN_STMT);
> +      t = expr_single (t);
> +      if (t && CAN_HAVE_LOCATION_P (t))
> +	SET_EXPR_LOCATION (t, loc);
>       }
>   }
>   
> +/* Like PROTECTED_SET_EXPR_LOCATION, but only do that if T has
> +   UNKNOWN_LOCATION.  */
> +
> +void
> +protected_set_expr_location_if_unset (tree t, location_t loc)
> +{
> +  t = expr_single (t);
> +  if (t && !EXPR_HAS_LOCATION (t))
> +    protected_set_expr_location (t, loc);
> +}
> +
>   /* Data used when collecting DECLs and TYPEs for language data removal.  */
>   
>   class free_lang_data_d
> --- gcc/cp/parser.c.jj	2020-04-02 12:53:41.542232631 +0200
> +++ gcc/cp/parser.c	2020-04-03 21:11:39.675843324 +0200
> @@ -39149,8 +39149,7 @@ cp_parser_omp_for_loop (cp_parser *parse
>   	    incr = cp_parser_omp_for_incr (parser, real_decl);
>   	  else
>   	    incr = cp_parser_expression (parser);
> -	  if (!EXPR_HAS_LOCATION (incr))
> -	    protected_set_expr_location (incr, input_location);
> +	  protected_set_expr_location_if_unset (incr, input_location);
>   	}
>   
>       parse_close_paren:
> --- gcc/cp/cp-gimplify.c.jj	2020-04-02 12:53:41.530232814 +0200
> +++ gcc/cp/cp-gimplify.c	2020-04-03 21:10:51.707548245 +0200
> @@ -226,8 +226,7 @@ genericize_if_stmt (tree *stmt_p)
>       stmt = else_;
>     else
>       stmt = build3 (COND_EXPR, void_type_node, cond, then_, else_);
> -  if (!EXPR_HAS_LOCATION (stmt))
> -    protected_set_expr_location (stmt, locus);
> +  protected_set_expr_location_if_unset (stmt, locus);
>     *stmt_p = stmt;
>   }
>   
> @@ -248,8 +247,7 @@ genericize_cp_loop (tree *stmt_p, locati
>     tree stmt_list = NULL;
>     tree debug_begin = NULL;
>   
> -  if (EXPR_LOCATION (incr) == UNKNOWN_LOCATION)
> -    protected_set_expr_location (incr, start_locus);
> +  protected_set_expr_location_if_unset (incr, start_locus);
>   
>     cp_walk_tree (&cond, cp_genericize_r, data, NULL);
>     cp_walk_tree (&incr, cp_genericize_r, data, NULL);
> --- gcc/testsuite/g++.dg/opt/pr94441.C.jj	2020-04-03 21:07:01.346933532 +0200
> +++ gcc/testsuite/g++.dg/opt/pr94441.C	2020-04-03 21:07:01.346933532 +0200
> @@ -0,0 +1,16 @@
> +// PR debug/94441
> +// { dg-do compile }
> +// { dg-options "-O3 -fno-forward-propagate --param=max-cse-insns=0 -flive-range-shrinkage -std=c++17 -fcompare-debug" }
> +
> +template <class,class> struct Same;
> +template <class T> struct Same<T,T> {};
> +
> +auto f()
> +{
> +  if constexpr (sizeof(int)==3)
> +    return 42;
> +  else
> +    return 42L;
> +}
> +
> +Same<decltype(f()), long> s;
> 
> 	Jakub
>