[cfe-commits] [llvm-commits] [PATCH] ARM ABI: handle varargs with vector types.

[manman ren]

Committed as r166040.
Thanks Eli for reviewing.

Manman

On Oct 16, 2012, at 11:53 AM, Eli Friedman <eli.friedman at gmail.com> wrote:

> On Tue, Oct 16, 2012 at 11:42 AM, Manman Ren <mren at apple.com> wrote:
>> 
>> On Oct 16, 2012, at 11:32 AM, Eli Friedman wrote:
>> 
>>> On Tue, Oct 16, 2012 at 11:10 AM, manman ren <mren at apple.com> wrote:
>>>> 
>>>> On Oct 15, 2012, at 5:59 PM, Eli Friedman <eli.friedman at gmail.com> wrote:
>>>> 
>>>>> On Mon, Oct 15, 2012 at 5:38 PM, Manman Ren <mren at apple.com> wrote:
>>>>>> 
>>>>>> On Oct 15, 2012, at 5:34 PM, Eli Friedman wrote:
>>>>>> 
>>>>>>> On Mon, Oct 15, 2012 at 5:26 PM, Manman Ren <mren at apple.com> wrote:
>>>>>>>> 
>>>>>>>> On Oct 15, 2012, at 5:11 PM, Eli Friedman wrote:
>>>>>>>> 
>>>>>>>>> On Mon, Oct 15, 2012 at 4:46 PM, manman ren <mren at apple.com> wrote:
>>>>>>>>>> 
>>>>>>>>>> The initial patch was updated and separated to two patches (attached).
>>>>>>>>>> 
>>>>>>>>>> The first patch will fix passing legal vector types as varargs:
>>>>>>>>>> We make sure the vector is correctly aligned before casting it to the vector type.
>>>>>>>>> 
>>>>>>>>> +  uint64_t Size = CGF.getContext().getTypeSize(Ty) / 8;
>>>>>>>>> +  uint64_t TyAlign = CGF.getContext().getTypeAlign(Ty) / 8;
>>>>>>>>> +
>>>>>>>>> +  // The ABI alignment for vectors is 8 for AAPCS and 4 for APCS.
>>>>>>>>> +  if (Ty->getAs<VectorType>() && Size >= 8) {
>>>>>>>>> +    if (getABIKind() == ARMABIInfo::AAPCS_VFP ||
>>>>>>>>> +        getABIKind() == ARMABIInfo::AAPCS)
>>>>>>>>> +      TyAlign = 8;
>>>>>>>>> +    else
>>>>>>>>> +      TyAlign = 4;
>>>>>>>>> +  }
>>>>>>>>> 
>>>>>>>>> We should be using the same rules here we do for argument passing.  In
>>>>>>>>> particular, for APCS, the argument-passing type alignment is
>>>>>>>>> unconditionally 4.  (This can have effects for structs marked with
>>>>>>>>> "__attribute__((aligned(16)))", etc.)
>>>>>>>> Is there an interface to query the argument-passing alignment?
>>>>>>> 
>>>>>>> Nothing cares about it other than the calling convention code, so
>>>>>>> there isn't a general API.  It's basically just "match whatever
>>>>>>> ARMABIInfo::classifyArgumentType does".
>>>>>> 
>>>>>> I don't see code in ARMABIInfo::classifyArgumentType that checks the argument-passing alignment.
>>>>>> The code in the patch is trying to match what the calling convention does in the backend:
>>>>> 
>>>>> Yes, it's a bit tricky because of the implicit contract between clang
>>>>> and the ARM backend... you basically have to combine the frontend and
>>>>> backend rules to figure out how the result is actually represented on
>>>>> the stack.  When you do that, it comes out to always 4 for APCS, and I
>>>>> think it comes out to min(max(naturalAlign, 4), 8) for AAPCS.
>>>> 
>>>> I think you are right, the patch is updated, please review again :]
>>> 
>>> +  if (Ty->getAs<VectorType>()) {
>>> 
>>> Why restrict the check to vector types?  (This check can have effects
>>> for other types, e.g. structs containing vectors.)
>> I want to make sure this patch only touches varargs with vector types.
>> For other types, we can handle those in a separate patch with additional testing cases.
> 
> Okay.
> 
> -Eli