On Tue, 8 Feb 2022, Jakub Jelinek wrote:
> Hi!
>
> As mentioned in the PR, since PR96690 r11-2834 we call rtl_for_decl_init
> which can call expand_expr already during early_dwarf. The comment and PR
> explains it that the intent is to ensure the referenced vars and functions
> are properly mangled because free_lang_data doesn't cover everything, like
> template parameters etc. It doesn't work well though, because expand_expr
free_lang_data mangling also only runs when generating LTO bytecode...
> can set DECL_RTLs e.g. on referenced vars and keep them there, and they can
> be created e.g. with different MEM_ALIGN compared to what they would be
> created with if they were emitted later.
> So, the following patch stops calling rtl_for_decl_init and instead
> for cases for which rtl_for_decl_init does anything at all walks the
> initializer and ensures referenced vars or functions are mangled.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2022-02-08 Jakub Jelinek <ja...@redhat.com>
>
> PR debug/104407
> * dwarf2out.cc (mangle_referenced_decls): New function.
> (tree_add_const_value_attribute): Don't call rtl_for_decl_init if
> early_dwarf. Instead walk the initializer and try to mangle vars or
> functions referenced from it.
>
> * g++.dg/debug/dwarf2/pr104407.C: New test.
>
> --- gcc/dwarf2out.cc.jj 2022-02-04 14:36:54.966605844 +0100
> +++ gcc/dwarf2out.cc 2022-02-07 12:28:13.000520666 +0100
> @@ -20881,6 +20881,19 @@ add_location_or_const_value_attribute (d
> return tree_add_const_value_attribute_for_decl (die, decl);
> }
>
> +/* Mangle referenced decls. */
> +static tree
> +mangle_referenced_decls (tree *tp, int *walk_subtrees, void *)
> +{
> + if (! EXPR_P (*tp) && ! CONSTANT_CLASS_P (*tp))
> + *walk_subtrees = 0;
> +
> + if (VAR_OR_FUNCTION_DECL_P (*tp))
> + assign_assembler_name_if_needed (*tp);
> +
> + return NULL_TREE;
> +}
> +
> /* Attach a DW_AT_const_value attribute to DIE. The value of the
> attribute is the const value T. */
>
> @@ -20889,7 +20902,6 @@ tree_add_const_value_attribute (dw_die_r
> {
> tree init;
> tree type = TREE_TYPE (t);
> - rtx rtl;
>
> if (!t || !TREE_TYPE (t) || TREE_TYPE (t) == error_mark_node)
> return false;
> @@ -20910,11 +20922,26 @@ tree_add_const_value_attribute (dw_die_r
> return true;
> }
> }
> - /* Generate the RTL even if early_dwarf to force mangling of all refered to
> - symbols. */
> - rtl = rtl_for_decl_init (init, type);
> - if (rtl && !early_dwarf)
> - return add_const_value_attribute (die, TYPE_MODE (type), rtl);
> + if (!early_dwarf)
> + {
> + rtx rtl = rtl_for_decl_init (init, type);
> + if (rtl && !early_dwarf)
the !early_dwarf is redundant
Otherwise looks good to me, please give Jason the opportunity to comment
though.
Thanks,
Richard.
> + return add_const_value_attribute (die, TYPE_MODE (type), rtl);
> + }
> + else
> + {
> + /* For early_dwarf force mangling of all referenced symbols. */
> + tree initializer = init;
> + STRIP_NOPS (initializer);
> + /* rtl_for_decl_init punts on other aggregates, and complex values. */
> + if (AGGREGATE_TYPE_P (type)
> + || (TREE_CODE (initializer) == VIEW_CONVERT_EXPR
> + && AGGREGATE_TYPE_P (TREE_TYPE (TREE_OPERAND (initializer, 0))))
> + || TREE_CODE (type) == COMPLEX_TYPE)
> + ;
> + else if (initializer_constant_valid_p (initializer, type))
> + walk_tree (&initializer, mangle_referenced_decls, NULL, NULL);
> + }
> /* If the host and target are sane, try harder. */
> if (CHAR_BIT == 8 && BITS_PER_UNIT == 8
> && initializer_constant_valid_p (init, type))
> --- gcc/testsuite/g++.dg/debug/dwarf2/pr104407.C.jj 2022-02-07
> 10:45:51.945041031 +0100
> +++ gcc/testsuite/g++.dg/debug/dwarf2/pr104407.C 2022-02-07
> 10:45:09.834635340 +0100
> @@ -0,0 +1,12 @@
> +// PR debug/104407
> +// { dg-do compile { target c++17 } }
> +// { dg-options "-O1 -fcompare-debug" }
> +
> +struct A { int i; long j; int k : 2; char l; } a;
> +
> +auto [ aa, bb, cc, dd ] = a;
> +
> +namespace N
> +{
> + auto & [ m, n, o, ppp ] = a;
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)
