Re: [patch] Fix PR middle-end/53590

[Richard Guenther <richard dot guenther at gmail dot com>]

On Fri, Jun 15, 2012 at 11:13 AM, Eric Botcazou <ebotcazou@adacore.com> wrote:
>> If we don't do it, we'll get another PR saying "this works in LTO mode with
>> other versions of the Ada compiler" (which is true) so I'll proceed.
>
> Here is what I've installed after bootstrapping/regtesting on x86_64-suse-linux
> and i586-suse-linux. ?It adds the flag to 'struct function' and streams it.

Btw, I think we should enable this flag by default for all languages but Java
so that if you enable -fnon-call-exceptions for C or C++ you don't get too
many spurious exceptions from dead code.

Thanks,
Richard.

> While I was at it, I also changed the trivially-dead-insns machinery in cse.c
> and dse.c to use the same predicate as dce.c, namely !insn_nothrow_p instead
> of insn_could_throw_p. ?The former is more precise and well suited to these
> optimization passes. ?cfgexpand.c and reload1.c keep using the latter when
> they are massaging the RTL stream.
>
>
> ? ? ? ?PR middle-end/53590
> ? ? ? ?* common.opt (-fdelete-dead-exceptions): New switch.
> ? ? ? ?* doc/invoke.texi (Code Gen Options): Document it.
> ? ? ? ?* cse.c (count_reg_usage) <CALL_INSN>: Use !insn_nothrow_p in lieu of
> ? ? ? ?insn_could_throw_p predicate. ?Do not skip an insn that could throw
> ? ? ? ?if dead exceptions can be deleted.
> ? ? ? ?(insn_live_p): Likewise, do not return true in that case.
> ? ? ? ?* dce.c (can_alter_cfg): New flag.
> ? ? ? ?(deletable_insn_p): Do not return false for an insn that can throw if
> ? ? ? ?the CFG can be altered and dead exceptions can be deleted.
> ? ? ? ?(init_dce): Set can_alter_cfg to false for fast DCE, true otherwise.
> ? ? ? ?* dse.c (scan_insn): Use !insn_nothrow_p in lieu of insn_could_throw_
> ? ? ? ?predicate. Do not preserve an insn that could throw if dead exceptions
> ? ? ? ?can be deleted.
> ? ? ? ?* function.h (struct function): Add can_delete_dead_exceptions flag.
> ? ? ? ?* function.c (allocate_struct_function): Set it.
> ? ? ? ?* lto-streamer-in.c (input_struct_function_base): Stream it.
> ? ? ? ?* lto-streamer-out.c (input_struct_function_base): Likewise.
> ? ? ? ?* tree-ssa-dce.c (mark_stmt_if_obviously_necessary): Do not mark a
> ? ? ? ?statement that could throw as necessary if dead exceptions can be
> ? ? ? ?deleted.
> ada/
> ? ? ? ?* gcc-interface/misc.c (gnat_init_options_struct): Set
> ? ? ? ?opts->x_flag_delete_dead_exceptions to 1.
>
>
> --
> Eric Botcazou