On Fri, Feb 28, 2014 at 9:42 AM, H.J. Lu <[email protected]> wrote:
> On Fri, Feb 28, 2014 at 9:25 AM, H.J. Lu <[email protected]> wrote:
>> On Fri, Feb 28, 2014 at 8:11 AM, H.J. Lu <[email protected]> wrote:
>>> On Fri, Feb 28, 2014 at 2:09 AM, Richard Biener
>>> <[email protected]> wrote:
>>>> On Fri, Feb 28, 2014 at 10:09 AM, Richard Biener
>>>> <[email protected]> wrote:
>>>>> On Fri, Feb 28, 2014 at 1:52 AM, H.J. Lu <[email protected]> wrote:
>>>>>> On Mon, Feb 24, 2014 at 9:12 PM, bin.cheng <[email protected]> wrote:
>>>>>>> Hi,
>>>>>>> This patch is to fix regression reported in PR60280 by removing forward
>>>>>>> loop
>>>>>>> headers/latches in cfg cleanup if possible. Several tests are broken by
>>>>>>> this change since cfg cleanup is shared by all optimizers. Some tests
>>>>>>> has
>>>>>>> already been fixed by recent patches, I went through and fixed the
>>>>>>> others.
>>>>>>> One case needs to be clarified is "gcc.dg/tree-prof/update-loopch.c".
>>>>>>> When
>>>>>>> GCC removing a basic block, it checks profile information by calling
>>>>>>> check_bb_profile after redirecting incoming edges of the bb. This
>>>>>>> certainly
>>>>>>> results in warnings about invalid profile information and causes the
>>>>>>> case to
>>>>>>> fail. I will send a patch to skip checking profile information for a
>>>>>>> removing basic block in stage 1 if it sounds reasonable. For now I just
>>>>>>> twisted the case itself.
>>>>>>>
>>>>>>> Bootstrap and tested on x86_64 and arm_a15.
>>>>>>>
>>>>>>> Is it OK?
>>>>>>>
>>>>>>>
>>>>>>> 2014-02-25 Bin Cheng <[email protected]>
>>>>>>>
>>>>>>> PR target/60280
>>>>>>> * tree-cfgcleanup.c (tree_forwarder_block_p): Protect loop
>>>>>>> preheaders and latches only if requested. Fix latch if it
>>>>>>> is removed.
>>>>>>> * tree-ssa-dom.c (tree_ssa_dominator_optimize): Set
>>>>>>> LOOPS_HAVE_PREHEADERS.
>>>>>>>
>>>>>>
>>>>>> This change:
>>>>>>
>>>>>> if (dest->loop_father->header == dest)
>>>>>> - return false;
>>>>>> + {
>>>>>> + if (loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS)
>>>>>> + && bb->loop_father->header != dest)
>>>>>> + return false;
>>>>>> +
>>>>>> + if (loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES)
>>>>>> + && bb->loop_father->header == dest)
>>>>>> + return false;
>>>>>> + }
>>>>>> }
>>>>>>
>>>>>> miscompiled 435.gromacs in SPEC CPU 2006 on x32 with
>>>>>>
>>>>>> -O3 -funroll-loops -ffast-math -fwhole-program -flto=jobserver
>>>>>> -fuse-linker-plugin
>>>>>>
>>>>>> This patch changes loops without LOOPS_HAVE_PREHEADERS
>>>>>> nor LOOPS_HAVE_SIMPLE_LATCHES from returning false to returning
>>>>>> true. I don't have a small testcase. But this patch:
>>>>>>
>>>>>> diff --git a/gcc/tree-cfgcleanup.c b/gcc/tree-cfgcleanup.c
>>>>>> index b5c384b..2ba673c 100644
>>>>>> --- a/gcc/tree-cfgcleanup.c
>>>>>> +++ b/gcc/tree-cfgcleanup.c
>>>>>> @@ -323,6 +323,10 @@ tree_forwarder_block_p (basic_block bb, bool
>>>>>> phi_wanted)
>>>>>> if (loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES)
>>>>>> && bb->loop_father->header == dest)
>>>>>> return false;
>>>>>> +
>>>>>> + if (!loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS)
>>>>>> + && !loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES))
>>>>>> + return false;
>>>>>> }
>>>>>> }
>>>>>>
>>>>>> fixes the regression. Does it make any senses?
>>>>>
>>>>> I think the preheader test isn't fully correct (bb may be in an inner loop
>>>>> for example). So a more conservative variant would be
>>>>>
>>>>> Index: gcc/tree-cfgcleanup.c
>>>>> ===================================================================
>>>>> --- gcc/tree-cfgcleanup.c (revision 208169)
>>>>> +++ gcc/tree-cfgcleanup.c (working copy)
>>>>> @@ -316,13 +316,13 @@ tree_forwarder_block_p (basic_block bb,
>>>>> /* Protect loop preheaders and latches if requested. */
>>>>> if (dest->loop_father->header == dest)
>>>>> {
>>>>> - if (loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS)
>>>>> - && bb->loop_father->header != dest)
>>>>> - return false;
>>>>> -
>>>>> - if (loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES)
>>>>> - && bb->loop_father->header == dest)
>>>>> - return false;
>>>>> + if (bb->loop_father == dest->loop_father)
>>>>> + return !loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES);
>>>>> + else if (bb->loop_father == loop_outer (dest->loop_father))
>>>>> + return !loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS);
>>>>> + /* Always preserve other edges into loop headers that are
>>>>> + not simple latches or preheaders. */
>>>>> + return false;
>>>>> }
>>>>> }
>>>>>
>>>>> that makes sure we can properly update loop information. It's also
>>>>> a more conservative change at this point which should still successfully
>>>>> remove simple latches and preheaders created by loop discovery.
>>>>
>>>> I think the patch makes sense anyway and thus I'll install it once it
>>>> passed bootstrap / regtesting.
>>>>
>>>> Another fix that may make sense is to restrict it to
>>>> !loops_state_satisfies_p (LOOPS_NEED_FIXUP), though cfgcleanup
>>>> itself can end up setting that ... which we eventually should fix if it
>>>> still happens. That is, check if
>>>>
>>>> Index: gcc/tree-cfgcleanup.c
>>>> ===================================================================
>>>> --- gcc/tree-cfgcleanup.c (revision 208169)
>>>> +++ gcc/tree-cfgcleanup.c (working copy)
>>>>
>>>> @@ -729,8 +729,9 @@ cleanup_tree_cfg_noloop (void)
>>>>
>>>> timevar_pop (TV_TREE_CLEANUP_CFG);
>>>>
>>>> - if (changed && current_loops)
>>>> - loops_state_set (LOOPS_NEED_FIXUP);
>>>> + if (changed && current_loops
>>>> + && !loops_state_satisfies_p (LOOPS_NEED_FIXUP))
>>>> + verify_loop_structure ();
>>>>
>>>> return changed;
>>>> }
>>>>
>>>> trips anywhere (and apply fixes). That's of course not appropriate at
>>>> this stage.
>>>>
>>>>> Does it fix 435.gromacs?
>>>
>>> I tried revision 208222 and it doesn't fix 435.gromacs.
>>
>> Remove
>>
>> else if (bb->loop_father == loop_outer (dest->loop_father))
>> return !loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS);
>
> Should we also check other loop state, like LOOPS_HAVE_SIMPLE_LATCHES
> or LOOPS_MAY_HAVE_MULTIPLE_LATCHES here?
>
This patch:
diff --git a/gcc/tree-cfgcleanup.c b/gcc/tree-cfgcleanup.c
index 926d300..fb1c63d 100644
--- a/gcc/tree-cfgcleanup.c
+++ b/gcc/tree-cfgcleanup.c
@@ -328,7 +328,9 @@ tree_forwarder_block_p (basic_block bb, bool phi_wanted)
(LOOPS_MAY_HAVE_MULTIPLE_LATCHES));
}
else if (bb->loop_father == loop_outer (dest->loop_father))
- return !loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS);
+ return (!loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS)
+ && !loops_state_satisfies_p
+ (LOOPS_MAY_HAVE_MULTIPLE_LATCHES));
/* Always preserve other edges into loop headers that are
not simple latches or preheaders. */
return false;
works. Does it look right?
--
H.J.
