Re: [PATCHv2] Add a couple of A?CST1:CST2 match and simplify optimizations

[Andrew MacLeod <amacleod@redhat.com>]

On 5/26/21 7:07 AM, Andrew Pinski wrote:
> On Wed, May 26, 2021 at 2:01 AM Andrew Pinski <pinskia@gmail.com> wrote:
>> On Wed, May 26, 2021 at 1:43 AM Bernd Edlinger
>> <bernd.edlinger@hotmail.de> wrote:
>>> On 5/25/21 4:22 PM, Richard Biener via Gcc-patches wrote:
>>>> On Sun, May 23, 2021 at 12:03 PM apinski--- via Gcc-patches
>>>> <gcc-patches@gcc.gnu.org> wrote:
>>>>> From: Andrew Pinski <apinski@marvell.com>
>>>>>
>>>>> Instead of some of the more manual optimizations inside phi-opt,
>>>>> it would be good idea to do a lot of the heavy lifting inside match
>>>>> and simplify instead. In the process, this moves the three simple
>>>>> A?CST1:CST2 (where CST1 or CST2 is zero) simplifications.
>>>>>
>>>>> OK? Boostrapped and tested on x86_64-linux-gnu with no regressions.
>>>>>
>>>>> Differences from V1:
>>>>> * Use bit_xor 1 instead of bit_not to fix the problem with boolean types
>>>>> which are not 1 bit precision.
>>>> OK.
>>>>
>>>> Thanks,
>>>> Richard.
>>>>
>>> Hmm, sorry, no luck.
>>>
>>> I think this caused:
>> If anything it is a bad interaction with changes between r12-1046 and
>> r12-1053; I am suspecting a bug in those changes rather than my
>> changes causing the bug.  Debugging it right now.
> (gdb) p debug_tree(name)
>   <ssa_name 0x7ffff6a5cd38
>      type <boolean_type 0x7ffff6b45b28 _Bool public unsigned QI
>          size <integer_cst 0x7ffff6b2bdc8 constant 8>
>          unit-size <integer_cst 0x7ffff6b2bde0 constant 1>
>          align:8 warn_if_not_align:0 symtab:0 alias-set -1
> canonical-type 0x7ffff6b45b28 precision:1 min <integer_cst
> 0x7ffff6b4a030 0> max <integer_cst 0x7ffff6b4a060 1>>
>
>      def_stmt _19 = ~_8;
>      version:19>
>
> So what is happening is evrp converted:
> ct_12 = ct_5 + -1;
> Into
> ct_12 = ct_5 == 1 ? 0 : 1;
> (this was done before my patch)
> And then it gets simplified to:
>    _8 = ct_5 == 1;
>    _19 = ~_8;
>    ct_12 = (int) _19;
> (after my match.pd patch)
>
> Which is correct, but the range code is not expecting new SSA names to
> be added .....
> It looks like the issue was introduced with r12-1048 (Add imports and
> strengthen the export definition in range_def and gori_map).
> I suspect there are other match.pd patterns which would also hit this
> issue where a new ssa name is introduced.
>
> I have no idea how to get this fixed because gimple-range-* is new to
> me; I tried looking into it but calling has_def_chain/get_def_chain
> inside register_dependency seems wrong, maybe Andrew MacLeod can help
> here.
> This happens even with a stage 1 gcc so it is not miscompiling.
>
> Also sorry for the breakage, I was not expecting it this time around
> as I ran bootstrap like three times and I did not expect an
> interaction with other parts of the compiler like this.
>
> Thanks,
> Andrew Pinski
>
>
>>
Yeah, not your fault, mine.  I'm sure it would have shown up very soon 
elsewhere, you were just the unlucky victim.

Sorry about that.

Andrew