Re: [PATCH] rs6000: Remove builtin mask check from builtin_decl [PR102347]

[Bill Schmidt <wschmidt@linux.ibm.com>]

Hi Kewen,

On 9/28/21 9:34 PM, Kewen.Lin wrote:
> Hi Bill,
>
> Thanks for your prompt comments!
>
> on 2021/9/29 上午3:24, Bill Schmidt wrote:
>> Hi Kewen,
>>
>> Although I agree that what we do now is tragically bad (and will be fixed in the builtin rewrite), this seems a little too cavalier to remove all checking during initialization without adding any checking somewhere else. :-)  We still need to check for invalid usage when the builtin is expanded, and I don't think the old code does this at all.
>>
> If I read the code right, there are some following places to check the invalid usage or not.
>   1) for folding, rs6000_gimple_fold_builtin -> rs6000_builtin_is_supported_p -> check mask
>                   -> defer to expand if invalid.
>   2) for expanding, obtain func_valid_p, error in rs6000_invalid_builtin.
>
> Both places seem to exist before the builtin rewrite, am I missing something?
>
> btw, I remembered I used one built gcc with my fix to compile one test case which is supposed to fail
> due to its invalid usage builtin at option -flto, it failed (errored) as expected but at LTRANS phase
> since it's the time to do expansion for no-fat-objs scenario.

OK.  If you are comfortable that this will be caught when the builtin is actually not valid, then I'll
withdraw my objection.  Can you test it?  I know that we've been trying to fix these cases piecemeal
in the old support, and as Peter says it's important to backport this, we need the solution.  I just
want to be sure we're not breaking something, and test coverage in this area is pretty terrible.

Thanks!
Bill

>
>> Unless you are planning to do a backport, I think the proper way forward here is to just wait for the new builtin support to land.  In the new code, we initialize all built-ins up front, and check properly at expansion time whether the builtin is enabled in the environment that obtains during expand.
> Good to know that!  Nice!  btw, for this issue itself, the current implementation (without rewriting)
> also initializes the built-ins in the table since MMA built-ins guarded in TARGET_EXTRA_BUILTINS,
> the root cause is the rs6000_builtin_mask can't set up (be switched) expectedly since the checking
> time is too early right when the built-in function_decl being created.
>
> BR,
> Kewen
>
>> My two cents,
>> Bill
>>
>> On 9/28/21 3:13 AM, Kewen.Lin wrote:
>>> Hi,
>>>
>>> As the discussion in PR102347, currently builtin_decl is invoked so
>>> early, it's when making up the function_decl for builtin functions,
>>> at that time the rs6000_builtin_mask could be wrong for those
>>> builtins sitting in #pragma/attribute target functions, though it
>>> will be updated properly later when LTO processes all nodes.
>>>
>>> This patch is to align with the practice i386 port adopts, also
>>> align with r10-7462 by relaxing builtin mask checking in some places.
>>>
>>> Bootstrapped and regress-tested on powerpc64le-linux-gnu P9 and
>>> powerpc64-linux-gnu P8.
>>>
>>> Is it ok for trunk?
>>>
>>> BR,
>>> Kewen
>>> -----
>>> gcc/ChangeLog:
>>>
>>> 	PR target/102347
>>> 	* config/rs6000/rs6000-call.c (rs6000_builtin_decl): Remove builtin
>>> 	mask check.
>>>
>>> gcc/testsuite/ChangeLog:
>>>
>>> 	PR target/102347
>>> 	* gcc.target/powerpc/pr102347.c: New test.
>>>
>>> ---
>>>  gcc/config/rs6000/rs6000-call.c             | 14 ++++----------
>>>  gcc/testsuite/gcc.target/powerpc/pr102347.c | 15 +++++++++++++++
>>>  2 files changed, 19 insertions(+), 10 deletions(-)
>>>  create mode 100644 gcc/testsuite/gcc.target/powerpc/pr102347.c
>>>
>>> diff --git a/gcc/config/rs6000/rs6000-call.c b/gcc/config/rs6000/rs6000-call.c
>>> index fd7f24da818..15e0e09c07d 100644
>>> --- a/gcc/config/rs6000/rs6000-call.c
>>> +++ b/gcc/config/rs6000/rs6000-call.c
>>> @@ -13775,23 +13775,17 @@ rs6000_init_builtins (void)
>>>      }
>>>  }
>>>
>>> -/* Returns the rs6000 builtin decl for CODE.  */
>>> +/* Returns the rs6000 builtin decl for CODE.  Note that we don't check
>>> +   the builtin mask here since there could be some #pragma/attribute
>>> +   target functions and the rs6000_builtin_mask could be wrong when
>>> +   this checking happens, though it will be updated properly later.  */
>>>
>>>  tree
>>>  rs6000_builtin_decl (unsigned code, bool initialize_p ATTRIBUTE_UNUSED)
>>>  {
>>> -  HOST_WIDE_INT fnmask;
>>> -
>>>    if (code >= RS6000_BUILTIN_COUNT)
>>>      return error_mark_node;
>>>
>>> -  fnmask = rs6000_builtin_info[code].mask;
>>> -  if ((fnmask & rs6000_builtin_mask) != fnmask)
>>> -    {
>>> -      rs6000_invalid_builtin ((enum rs6000_builtins)code);
>>> -      return error_mark_node;
>>> -    }
>>> -
>>>    return rs6000_builtin_decls[code];
>>>  }
>>>
>>> diff --git a/gcc/testsuite/gcc.target/powerpc/pr102347.c b/gcc/testsuite/gcc.target/powerpc/pr102347.c
>>> new file mode 100644
>>> index 00000000000..05c439a8dac
>>> --- /dev/null
>>> +++ b/gcc/testsuite/gcc.target/powerpc/pr102347.c
>>> @@ -0,0 +1,15 @@
>>> +/* { dg-do link } */
>>> +/* { dg-require-effective-target power10_ok } */
>>> +/* { dg-require-effective-target lto } */
>>> +/* { dg-options "-flto -mdejagnu-cpu=power9" } */
>>> +
>>> +/* Verify there are no error messages in LTO mode.  */
>>> +
>>> +#pragma GCC target "cpu=power10"
>>> +int main ()
>>> +{
>>> +  float *b;
>>> +  __vector_quad c;
>>> +  __builtin_mma_disassemble_acc (b, &c);
>>> +  return 0;
>>> +}
>>> --
>>> 2.27.0
>>>
>