Re: [PATCH][C++] Remove 99% calls to expr*location

[Richard Guenther <rguenther at suse dot de>]

On Wed, 28 Mar 2007, Richard Guenther wrote:

> 
> This removes 99% of the calls to expr_has_location, expr_locus and
> expr_location.  Currently the cp_walk_subtrees subroutine saves and
> restores the input_location for every subtree visited (!) for the
> appearant reason
> 
> -   /* Set input_location here so we get the right instantiation context
> -      if we call instantiate_decl from inlinable_function_p.  */
> -   save_locus = input_location;
> -   if (EXPR_HAS_LOCATION (*tp))
> -     input_location = EXPR_LOCATION (*tp);
> 
> but instantiate_decl is never called from the walk tree, but only from the
> cannot_inline_tree_fn langhook.  inlinable_function_p looks like:
> 
> static bool
> inlinable_function_p (tree fn)
> {
> ...
>   inlinable = !lang_hooks.tree_inlining.cannot_inline_tree_fn (&fn);
> ...
>   else if (inline_forbidden_p (fn))
>     {
> ...
> 
> where only inline_forbidden_p does a walk_tree.  I fail to see why
> we should punish 99% of walk_tree just for this case, given that
> instantiate_decl only writes to input_location as well.
> 
> Maybe someone remebers why this was necessary?  The following patch
> get's all of expr_location stuff off the profiling radar (so no need
> for me to optimize it, which can be done, too, see the 2nd patch after
> the first one).

The locus saving was introduced by the tree-ssa merge and there by

Branch: 	tree-ssa-20020619-branch
Changes by:	rth@gcc.gnu.org	2004-04-19 17:38:43

Modified files:
	gcc            : c-common.c 
	gcc/cp         : ChangeLog.tree-ssa except.c tree.c 

Log message:
	* c-common.c (c_walk_subtrees): Save and restore input_location.
	cp/
	* except.c (check_handlers_1): Use locus stored in master for 
warning.
	* tree.c (cp_walk_subtrees): Save and restore input_location.

but I don't see the c-common.c part ever reached mainline (at least it
doesn't appear in the tree-ssa changelog) and c_walk_subtree was removed
by

2004-06-26  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>

        * c-common.c (c_safe_from_p, c_walk_subtrees): Deleted.
        * c-common.def (DECL_STMT): Remove.
        * c-common.h (DECL_STMT_DECL): Deleted.
        (COMPOUNT_LITERAL_EXPR_DECL): Use DECL_EXPR_DECL.
        (c_safe_from_p, c_walk_subtrees): Deleted.
...

-  /* Set input_location here so we get the right instantiation context
-     if we call instantiate_decl from inlinable_function_p.  */
-  save_locus = input_location;
-  if (EXPR_LOCUS (*tp))
-    input_location = *EXPR_LOCUS (*tp);

so maybe it's just an oversight the cp variant survived?

Richard.