Re: [PATCH] Fix compile-time hog in MPX boundary checking (PR target/84988).

[Martin Liška <mliska at suse dot cz>]

On 03/21/2018 10:39 AM, Martin Liška wrote:
> On 03/21/2018 10:36 AM, Richard Biener wrote:
> > On Tue, Mar 20, 2018 at 10:44 PM, Richard Sandiford
> > <richard.sandiford@linaro.org> wrote:
> > > Jeff Law <law@redhat.com> writes:
> > > > On 03/20/2018 01:36 PM, Martin Liška wrote:
> > > > > Hi.
> > > > >
> > > > > This is a work-around to not iterate all members of array that can be huge.
> > > > > As MPX will be removed in GCC 9.x, I hope it's acceptable. I don't want
> > > > > to come
> > > > > up with a new param for it.
> > > > >
> > > > > Survives tests&bootstrap on x86_64-linux-gnu.
> > > > >
> > > > > Martin
> > > > >
> > > > > gcc/ChangeLog:
> > > > >
> > > > > 2018-03-20  Martin Liska  <mliska@suse.cz>
> > > > >
> > > > >      PR target/84988
> > > > >      * tree-chkp.c (CHKP_ARRAY_MAX_CHECK_STEPS): Define a new macro.
> > > > >      (chkp_find_bound_slots_1): Limit number of iterations.
> > > > Or just CLOSE/WONTFIX :-)
> > > >
> > > > I've got no objections here -- we want to  minimize the effort put into
> > > > CHKP given its going to be deprecated.
> > >
> > > The problem is that this affects normal configs, not just ones with
> > > MPX enabled.
> >
> > Indeed.  It get's called via
> >
> > #0  chkp_find_bound_slots_1 (type=0x7ffff69ee9d8, have_bound=0x2ed3868, offs=0)
> >      at /space/rguenther/src/svn/early-lto-debug/gcc/tree-chkp.c:1708
> > #1  0x0000000001379a13 in chkp_find_bound_slots (type=0x7ffff69ee9d8,
> >      res=0x2ed3868)
> >      at /space/rguenther/src/svn/early-lto-debug/gcc/tree-chkp.c:1754
> > #2  0x0000000001377054 in chkp_type_bounds_count (type=0x7ffff69ee9d8)
> >      at /space/rguenther/src/svn/early-lto-debug/gcc/tree-chkp.c:1009
> > #3  0x00000000016c664f in ix86_function_arg_advance (cum_v=...,
> >      mode=E_BLKmode, type=0x7ffff69ee9d8, named=true)
> >      at /space/rguenther/src/svn/early-lto-debug/gcc/config/i386/i386.c:8621
> > 8616        {
> > 8617          /* Track if there are outgoing arguments on stack.  */
> > 8618          if (cum->caller)
> > 8619            cfun->machine->outgoing_args_on_stack = true;
> > 8620
> > 8621          cum->bnds_in_bt = chkp_type_bounds_count (type);
> > 8622        }
> > 8623    }
> > 8624
> > 8625    /* Define where to put the arguments to a function.
> >
> > but I think we know POINTER_BOUNDS_TYPE_P etc. never return
> > true if -fcheck-pointer-* or -mmpx is not enabled, right?  So we can
> > guard the above call appropriately and save some compile-time
> > for all of us?
>
> Good observation, let me enhance the patch for the PR.
>
> Martin
>
> > Richard.
> >
> > > Thanks,
> > > Richard

Hi.

I've got this, that survives bootstrap&regression tests on x86_64-linux-gnu.

May I install it?
Thanks,
Martin

>From 15f95ac5117d9e2bab96c725716e5cb2832d3589 Mon Sep 17 00:00:00 2001
From: marxin <mliska@suse.cz>
Date: Wed, 21 Mar 2018 10:51:32 +0100
Subject: [PATCH] Do not call chkp_type_bounds_count if MPX is not enabled (PR
 target/84988).

gcc/ChangeLog:

2018-03-21  Martin Liska  <mliska@suse.cz>

	PR target/84988
	* config/i386/i386.c (ix86_function_arg_advance): Do not call
	chkp_type_bounds_count if MPX is not enabled.
---
 gcc/config/i386/i386.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 5b1e962dedb..0693f8fc451 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -8618,7 +8618,8 @@ ix86_function_arg_advance (cumulative_args_t cum_v, machine_mode mode,
       if (cum->caller)
 	cfun->machine->outgoing_args_on_stack = true;
 
-      cum->bnds_in_bt = chkp_type_bounds_count (type);
+      if (type && POINTER_BOUNDS_TYPE_P (type))
+	cum->bnds_in_bt = chkp_type_bounds_count (type);
     }
 }
 
-- 
2.16.2