On Thu, Jan 19, 2017 at 6:22 PM, David Malcolm <dmalc...@redhat.com> wrote:
> On Mon, 2017-01-16 at 14:42 -0700, Jeff Law wrote:
>> On 01/09/2017 07:38 PM, David Malcolm wrote:
>> > gcc/ChangeLog:
>> > * passes.c: Include "insn-addr.h".
>> > (should_skip_pass_p): Add logging. Update logic for running
>> > "expand" to be compatible with both __GIMPLE and __RTL. Guard
>> > property-provider override so it is only done for gimple
>> > passes.
>> > Don't skip dfinit.
>> > (skip_pass): New function.
>> > (execute_one_pass): Call skip_pass when skipping passes.
>> > ---
>> > gcc/passes.c | 65
>> > +++++++++++++++++++++++++++++++++++++++++++++++++++++-------
>> > 1 file changed, 58 insertions(+), 7 deletions(-)
>> >
>> > diff --git a/gcc/passes.c b/gcc/passes.c
>> > index 31262ed..6954d1e 100644
>> > --- a/gcc/passes.c
>> > +++ b/gcc/passes.c
>> > @@ -59,6 +59,7 @@ along with GCC; see the file COPYING3. If not
>> > see
>> > #include "cfgrtl.h"
>> > #include "tree-ssa-live.h" /* For remove_unused_locals. */
>> > #include "tree-cfgcleanup.h"
>> > +#include "insn-addr.h" /* for INSN_ADDRESSES_ALLOC. */
>> insn-addr? Yuk.
>>
>>
>> >
>> > using namespace gcc;
>> >
>> > @@ -2315,26 +2316,73 @@ should_skip_pass_p (opt_pass *pass)
>> > if (!cfun->pass_startwith)
>> > return false;
>> >
>> > - /* We can't skip the lowering phase yet -- ideally we'd
>> > - drive that phase fully via properties. */
>> > - if (!(cfun->curr_properties & PROP_ssa))
>> > - return false;
>> > + /* For __GIMPLE functions, we have to at least start when we
>> > leave
>> > + SSA. */
>> > + if (pass->properties_destroyed & PROP_ssa)
>> > + {
>> > + if (!quiet_flag)
>> > + fprintf (stderr, "starting anyway when leaving SSA: %s\n",
>> > pass->name);
>> > + cfun->pass_startwith = NULL;
>> > + return false;
>> > + }
>> This seems to need a comment -- it's not obvious how destroying the
>> SSA
>> property maps to a pass that can not be skipped.
>
> Added:
>
> /* For __GIMPLE functions, we have to at least start when we leave
> SSA. Hence, we need to detect the "expand" pass, and stop skipping
> when we encounter it. A cheap way to identify "expand" is it to
> detect the destruction of PROP_ssa.
> For __RTL functions, we invoke "rest_of_compilation" directly, which
> is after "expand", and hence we don't reach this conditional. */
>
>> > - /* And also run any property provider. */
>> > - if (pass->properties_provided != 0)
>> > + /* Run any property provider. */
>> > + if (pass->type == GIMPLE_PASS
>> > + && pass->properties_provided != 0)
>> > return false;
>> So comment needed here too. I read this as "if a gimple pass
>> provides a
>> property then it should not be skipped. Which means that an RTL pass
>> that provides a property can?
>
> Added:
>
> /* For GIMPLE passes, run any property provider (but continue skipping
> afterwards).
> We don't want to force running RTL passes that are property providers:
> "expand" is covered above, and the only pass other than "expand" that
> provides a property is "into_cfglayout" (PROP_cfglayout), which does
> too much for a dumped __RTL function. */
>
> ...the problem being that into_cfglayout's execute vfunc calls
> cfg_layout_initialize, which does a lot more that just
> cfg_layout_rtl_register_cfg_hooks (the skip hack does just the latter).
>
>> > + /* Don't skip df init; later RTL passes need it. */
>> > + if (strstr (pass->name, "dfinit") != NULL)
>> > + return false;
>> Which seems like a failing in RTL passes saying they need DF init.
>
> There isn't a "PROP_df"; should there be?
> Or is this hack accepable?
>
>> > +/* Skip the given pass, for handling passes before "startwith"
>> > + in __GIMPLE and__RTL-marked functions.
>> > + In theory, this ought to be a no-op, but some of the RTL passes
>> > + need additional processing here. */
>> > +
>> > +static void
>> > +skip_pass (opt_pass *pass)
>> ...
>> This all feels like a failing in how we handle state in the RTL
>> world.
>> And I suspect it's prone to error. Imagine if I'm hacking on
>> something
>> in the RTL world and my code depends on something else being set up.
>> I
>> really ought to have a way within my pass to indicate what I depend
>> on.
>> Having it hidden away in passes.c makes it easy to miss/forget.
>
> Indeed, it's a hack. I preferred the vfunc idea, but Richi prefers
> to keep it all in one place.
>
>> > +{
>> > + /* Pass "reload" sets the global "reload_completed", and many
>> > + things depend on this (e.g. instructions in .md files). */
>> > + if (strcmp (pass->name, "reload") == 0)
>> > + reload_completed = 1;
>> Seems like this ought to be a property provided by LRA/reload.
>
> If we have a __RTL function with a "startwith" of a pass after reload,
> we don't want to run "reload" when iterating through the pass list to
> reach the start pass, since presumably it could change the insns. So
> if LRA/reload provide a property, say PROP_reload_completed, we'd still
> need a way to *not* run reload, whilst setting the reload_completed
> global. So I don't think that a property necessarily buys us much
> here (it'd still be a hack either way...).
>
> Or is your observation more about having a way to identify the pass
> without doing a strcmp?
>
>> > +
>> > + /* The INSN_ADDRESSES vec is normally set up by
>> > + shorten_branches; set it up for the benefit of passes that
>> > + run after this. */
>> > + if (strcmp (pass->name, "shorten") == 0)
>> > + INSN_ADDRESSES_ALLOC (get_max_uid ());
>> Similarly ought to be provided by shorten-branches
>
> Similar to the reload_completed discussion above.
>
>
>> > +
>> > + /* Update the cfg hooks as appropriate. */
>> > + if (strcmp (pass->name, "into_cfglayout") == 0)
>> > + {
>> > + cfg_layout_rtl_register_cfg_hooks ();
>> > + cfun->curr_properties |= PROP_cfglayout;
>> > + }
>> > + if (strcmp (pass->name, "outof_cfglayout") == 0)
>> > + {
>> > + rtl_register_cfg_hooks ();
>> > + cfun->curr_properties &= ~PROP_cfglayout;
>> > + }
>> > +}
>> This feels somewhat different, but still a hack.
>>
>> I don't have strong suggestions on how to approach this, but what
>> we've
>> got here feels like a hack and one prone to bitrot.
>
> Given that Richi seems to prefer the "contain it all in once place"
> to the virtual function idea, there's not much more I can offer to fix it.
>
> Updated version of the patch attached (just adding the missing comments)
>
> Is this version OK?
Ok.
Richard.
> Changed in v2:
> - added some comments to should_skip_pass_p
>
> gcc/ChangeLog:
> * passes.c: Include "insn-addr.h".
> (should_skip_pass_p): Add logging. Update logic for running
> "expand" to be compatible with both __GIMPLE and __RTL. Guard
> property-provider override so it is only done for gimple passes.
> Don't skip dfinit.
> (skip_pass): New function.
> (execute_one_pass): Call skip_pass when skipping passes.
> ---
> gcc/passes.c | 74
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++------
> 1 file changed, 67 insertions(+), 7 deletions(-)
>
> diff --git a/gcc/passes.c b/gcc/passes.c
> index 31262ed..9886693 100644
> --- a/gcc/passes.c
> +++ b/gcc/passes.c
> @@ -59,6 +59,7 @@ along with GCC; see the file COPYING3. If not see
> #include "cfgrtl.h"
> #include "tree-ssa-live.h" /* For remove_unused_locals. */
> #include "tree-cfgcleanup.h"
> +#include "insn-addr.h" /* for INSN_ADDRESSES_ALLOC. */
>
> using namespace gcc;
>
> @@ -2315,26 +2316,82 @@ should_skip_pass_p (opt_pass *pass)
> if (!cfun->pass_startwith)
> return false;
>
> - /* We can't skip the lowering phase yet -- ideally we'd
> - drive that phase fully via properties. */
> - if (!(cfun->curr_properties & PROP_ssa))
> - return false;
> + /* For __GIMPLE functions, we have to at least start when we leave
> + SSA. Hence, we need to detect the "expand" pass, and stop skipping
> + when we encounter it. A cheap way to identify "expand" is it to
> + detect the destruction of PROP_ssa.
> + For __RTL functions, we invoke "rest_of_compilation" directly, which
> + is after "expand", and hence we don't reach this conditional. */
> + if (pass->properties_destroyed & PROP_ssa)
> + {
> + if (!quiet_flag)
> + fprintf (stderr, "starting anyway when leaving SSA: %s\n",
> pass->name);
> + cfun->pass_startwith = NULL;
> + return false;
> + }
>
> if (determine_pass_name_match (pass->name, cfun->pass_startwith))
> {
> + if (!quiet_flag)
> + fprintf (stderr, "found starting pass: %s\n", pass->name);
> cfun->pass_startwith = NULL;
> return false;
> }
>
> - /* And also run any property provider. */
> - if (pass->properties_provided != 0)
> + /* For GIMPLE passes, run any property provider (but continue skipping
> + afterwards).
> + We don't want to force running RTL passes that are property providers:
> + "expand" is covered above, and the only pass other than "expand" that
> + provides a property is "into_cfglayout" (PROP_cfglayout), which does
> + too much for a dumped __RTL function. */
> + if (pass->type == GIMPLE_PASS
> + && pass->properties_provided != 0)
> return false;
>
> + /* Don't skip df init; later RTL passes need it. */
> + if (strstr (pass->name, "dfinit") != NULL)
> + return false;
> +
> + if (!quiet_flag)
> + fprintf (stderr, "skipping pass: %s\n", pass->name);
> +
> /* If we get here, then we have a "startwith" that we haven't seen yet;
> skip the pass. */
> return true;
> }
>
> +/* Skip the given pass, for handling passes before "startwith"
> + in __GIMPLE and__RTL-marked functions.
> + In theory, this ought to be a no-op, but some of the RTL passes
> + need additional processing here. */
> +
> +static void
> +skip_pass (opt_pass *pass)
> +{
> + /* Pass "reload" sets the global "reload_completed", and many
> + things depend on this (e.g. instructions in .md files). */
> + if (strcmp (pass->name, "reload") == 0)
> + reload_completed = 1;
> +
> + /* The INSN_ADDRESSES vec is normally set up by
> + shorten_branches; set it up for the benefit of passes that
> + run after this. */
> + if (strcmp (pass->name, "shorten") == 0)
> + INSN_ADDRESSES_ALLOC (get_max_uid ());
> +
> + /* Update the cfg hooks as appropriate. */
> + if (strcmp (pass->name, "into_cfglayout") == 0)
> + {
> + cfg_layout_rtl_register_cfg_hooks ();
> + cfun->curr_properties |= PROP_cfglayout;
> + }
> + if (strcmp (pass->name, "outof_cfglayout") == 0)
> + {
> + rtl_register_cfg_hooks ();
> + cfun->curr_properties &= ~PROP_cfglayout;
> + }
> +}
> +
> /* Execute PASS. */
>
> bool
> @@ -2375,7 +2432,10 @@ execute_one_pass (opt_pass *pass)
> }
>
> if (should_skip_pass_p (pass))
> - return true;
> + {
> + skip_pass (pass);
> + return true;
> + }
>
> /* Pass execution event trigger: useful to identify passes being
> executed. */
> --
> 1.8.5.3
>
