Re: RFC: Preserving order of functions and top-level asms via cgraph

[Marcin Dalecki <martin at dalecki dot de>]

On 2005-04-11, at 14:43, Giovanni Bajo wrote:

> Marcin Dalecki <martin@dalecki.de> wrote:
>
> > On i386 you will find:
> >
> > # Disable unit-at-a-time mode, it makes gcc use a lot more stack
> > # due to the lack of sharing of stacklots.
> > CFLAGS += $(call cc-option,-fno-unit-at-a-time)
>
> This is no longer true in 4.0, because of this patch:
>
> 2004-09-03  Richard Henderson  <rth@redhat.com>
>
>         PR middle-end/9997
>         * cfgexpand.c (LOCAL_ALIGNMENT): Provide default.
>         (STACK_ALIGNMENT_NEEDED, FRAME_GROWS_DOWNWARD): Likewise.
>         (struct stack_var, EOC, stack_vars, stack_vars_alloc,
> stack_vars_num,
>         stack_vars_sorted, stack_vars_conflict, 
> stack_vars_conflict_alloc,
>         frame_phase, get_decl_align_unit, add_stack_var, 
> triangular_index,
>         resize_stack_vars_conflict, add_stack_var_conflict,
>         stack_var_conflict_p, add_alias_set_conflicts, 
> stack_var_size_cmp,
>         union_stack_vars, partition_stack_vars, 
> dump_stack_var_partition,
>         expand_one_stack_var_at, expand_stack_vars, 
> expand_one_stack_var,
>         expand_one_static_var, expand_one_hard_reg_var,
>         expand_one_register_var, expand_one_error_var,
> defer_stack_allocation,
>         expand_one_var, expand_used_vars_for_block, clear_tree_used): 
> New.
>         (expand_used_vars): Rewrite.
>         * Makefile.in (cfgexpand.o): Update dependencies.
>
> We now coalesce stack slots again and better than what GCC ever did.

OK thanks for confirming my suspicion that this was just an confused
micro-optimization.