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

[Daniel Dunbar]

On Mon, Sep 27, 2010 at 11:58 AM, Sandeep Patel <deeppatel1987 at gmail.com> wrote:
> 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.

I can't remember if I have made this offer publicly before, but as a
general rule if someone donates to me a fast machine which otherwise
has Clang support, I will implement the ABI for it. You can't have it
back though. :)

 - Daniel

> deep
>