[cfe-commits] r114618 - in /cfe/trunk: lib/CodeGen/TargetInfo.cpp test/CodeGen/arm-vector-arguments.c

[Sandeep Patel]

On Fri, Sep 24, 2010 at 1:52 AM, Daniel Dunbar <daniel at zuster.org> wrote:
> On Thu, Sep 23, 2010 at 3:42 PM, Eli Friedman <eli.friedman at gmail.com> wrote:
>> On Wed, Sep 22, 2010 at 6:54 PM, Daniel Dunbar <daniel at zuster.org> wrote:
>>> Author: ddunbar
>>> Date: Wed Sep 22 20:54:28 2010
>>> New Revision: 114618
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=114618&view=rev
>>> Log:
>>> IRgen/ABI/ARM: Trust the backend to pass vectors correctly for the given ABI.
>>>  - Therefore, we can lower out the NEON wrapper structs and pass the vectors
>>>   directly. This makes a huge difference in the cleanliness of the IR after
>>>   optimization.
>>>  - I will trust, but verify, via future ABITest testing (for APCS-GNU, at
>>>   least).
>>>
>>> Added:
>>>    cfe/trunk/test/CodeGen/arm-vector-arguments.c
>>> Modified:
>>>    cfe/trunk/lib/CodeGen/TargetInfo.cpp
>>>
>>> Modified: cfe/trunk/lib/CodeGen/TargetInfo.cpp
>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/TargetInfo.cpp?rev=114618&r1=114617&r2=114618&view=diff
>>> ==============================================================================
>>> --- cfe/trunk/lib/CodeGen/TargetInfo.cpp (original)
>>> +++ cfe/trunk/lib/CodeGen/TargetInfo.cpp Wed Sep 22 20:54:28 2010
>>> @@ -2272,6 +2272,17 @@
>>>   if (isRecordWithNonTrivialDestructorOrCopyConstructor(Ty))
>>>     return ABIArgInfo::getIndirect(0, /*ByVal=*/false);
>>>
>>> +  // NEON vectors are implemented as (theoretically) opaque structures wrapping
>>> +  // the underlying vector type. We trust the backend to pass the underlying
>>> +  // vectors appropriately, so we can unwrap the structs which generally will
>>> +  // lead to much cleaner IR.
>>> +  if (const Type *SeltTy = isSingleElementStruct(Ty, getContext())) {
>>> +    if (SeltTy->isVectorType())
>>> +      return ABIArgInfo::getDirect(CGT.ConvertType(QualType(SeltTy, 0)));
>>> +  }
>>
>> Err, don't you actually need to check that the target supports NEON
>> and that the vectors in question are actually NEON vectors?
>
> I don't think so, I believe they both should be passed the same way in
> both ABIs, but this gives cleaner IR. This assumes the backend honors
> the ABI correctly, of course.
>
> I don't know too much about the AAPCS ABI, however, so I could be wrong.

This is going to be wrong on AAPCS-VFP where there are specific rules
for how structures containing vectors are to be passed in vector
registers or memory.

Doing all the AAPCS-VFP rules in Clang is on my long list of stuff I'd
eventually like to get to, so if somebody else is motivated, please
jump in first if you have the cycles.

deep