llvm dev - Oct 2012 - [LLVMdev] vselect on ARM/NEON

Hello,

We've run into a couple of cases where we'd like to use select on vector
types, but vselect handling is absent from the ARM backend.
Would there be any potential harm by marking VSELECT as Expand on ARM 
targets with NEON?
Adding this seems to fix the following PR's:

http://llvm.org/bugs/show_bug.cgi?id=13831
http://llvm.org/bugs/show_bug.cgi?id=13961

Thanks!

Pete

Seems reasonable to me. Plain 'SELECT' is already marked expand for
vector types. I bet that just didn't get updates when VSELECT was
introduced.

-Jim

On Oct 11, 2012, at 10:25 AM, Peter Couperus <peter.couperus at st.com>
wrote:
> Hello,
> 
> We've run into a couple of cases where we'd like to use select on
vector types, but vselect handling is absent from the ARM backend.
> Would there be any potential harm by marking VSELECT as Expand on ARM
targets with NEON?
> Adding this seems to fix the following PR's:
> 
> http://llvm.org/bugs/show_bug.cgi?id=13831
> http://llvm.org/bugs/show_bug.cgi?id=13961
> 
> Thanks!
> 
> Pete
> 
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

If you mark VSELECT as 'expand' then it will be expanded to a sequence
of AND/OR/XOR, which is pretty efficient (found in LegalizeVectorOps.cpp
ExpandVSELECT).


On Oct 11, 2012, at 11:05 AM, Jim Grosbach <grosbach at apple.com> wrote:
> Seems reasonable to me. Plain 'SELECT' is already marked expand for
vector types. I bet that just didn't get updates when VSELECT was
introduced.
> 
> -Jim
> 
> On Oct 11, 2012, at 10:25 AM, Peter Couperus <peter.couperus at
st.com> wrote:
> 
>> Hello,
>> 
>> We've run into a couple of cases where we'd like to use select
on vector types, but vselect handling is absent from the ARM backend.
>> Would there be any potential harm by marking VSELECT as Expand on ARM
targets with NEON?
>> Adding this seems to fix the following PR's:
>> 
>> http://llvm.org/bugs/show_bug.cgi?id=13831
>> http://llvm.org/bugs/show_bug.cgi?id=13961
>> 
>> Thanks!
>> 
>> Pete
>> 
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> 
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev