Re: [patch] Fix PR rtl-optimization/54870

[Eric Botcazou <ebotcazou at adacore dot com>]

> Where is mark_addressable called?  It's wrong (and generally impossible) to
> do that late.

In expr.c:emit_block_move_hints.  It's one of the calls added to support the 
enhanced DSE last year, there are others in calls.c for example.

> If you only have memcpy then escaped will be empty.  fixing escaped is
> not the right solution (it may work for some reason in this case though).
> The rtl code has to approximate ref_maybe_used_by_call_p in a conservative
> way which it doesn't seem to do correctly (I don't remember a RTL alias.c
> interface that would match this, or ref_maybe_used_by_stmt_p - maybe
> we should add one?)

I'm OK with the new bitmap + decls_to_pointers idea.  Keep in mind that the 
info needs to be updated after update_alias_info_with_stack_vars, because for

MEM[(c_char * {ref-all})&i] = MEM[(c_char * {ref-all})&A.17];

you don't know until expand whether this will a memcpy or a move by pieces and 
the info is needed for the enhanced DSE to work properly.

-- 
Eric Botcazou