[llvm-commits] [llvm] r99549 - /llvm/trunk/lib/Target/ARM/ARMSubtarget.cpp

[Evan Cheng]

On Mar 25, 2010, at 4:13 PM, Jim Grosbach wrote:

> 
> On Mar 25, 2010, at 3:43 PM, Evan Cheng wrote:
> 
>> 
>> On Mar 25, 2010, at 1:57 PM, Jim Grosbach wrote:
>> 
>>> I'll look at the x86 stuff and see if there's a better approach that'll work here. Thanks for the pointer. I agree having the conditional like this is a bit "eww."
>>> 
>>> That said, I went with this for two reasons: it's consistent with what we already do for the NEON-for-scalar-math flag, and we only want to disable the instructions for specific CPUs (cortex-a8 for now), not whole architecture variants, and as far as I know, the CPUString flag is the only place we have that information.
>> 
>> You can specify features for individual cpu's. I think that's a cleaner way to go about it.
>> 
> 
> Done in r99565. Great suggestion. I like that a lot better.
> 
> Should we do the same for the UseNEONForSinglePrecisionFP flag, do you think?

Yes, I think so. Thanks.

Evan

> 
>> Evan
>> 
>>> 
>>> 
>>> On Mar 25, 2010, at 1:54 PM, Evan Cheng wrote:
>>> 
>>>> Thanks Jim. But perhaps this can be a subtarget feature specified in ARM.td? For example, x86 has FeatureSlowBTMem which disables uses of certain instructions for specific variants.
>>>> 
>>>> Evan
>>>> 
>>>> On Mar 25, 2010, at 1:48 PM, Jim Grosbach wrote:
>>>> 
>>>>> Author: grosbach
>>>>> Date: Thu Mar 25 15:48:50 2010
>>>>> New Revision: 99549
>>>>> 
>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=99549&view=rev
>>>>> Log:
>>>>> ARM cortex-a8 doesn't do vmla/vmls well. disable them by default for that cpu
>>>>> 
>>>>> Modified:
>>>>> llvm/trunk/lib/Target/ARM/ARMSubtarget.cpp
>>>>> 
>>>>> Modified: llvm/trunk/lib/Target/ARM/ARMSubtarget.cpp
>>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMSubtarget.cpp?rev=99549&r1=99548&r2=99549&view=diff
>>>>> ==============================================================================
>>>>> --- llvm/trunk/lib/Target/ARM/ARMSubtarget.cpp (original)
>>>>> +++ llvm/trunk/lib/Target/ARM/ARMSubtarget.cpp Thu Mar 25 15:48:50 2010
>>>>> @@ -127,6 +127,12 @@
>>>>> // operations with NEON instructions.
>>>>> if (UseNEONFP.getPosition() == 0)
>>>>>   UseNEONForSinglePrecisionFP = true;
>>>>> +    // The VFP vlma and vlms instructions don't play nicely with others;
>>>>> +    // disable them.
>>>>> +    // FIXME: This may be true for other variants as well. Get benchmark
>>>>> +    // numbers and add them if determined that's the case.
>>>>> +    if (UseVMLxInstructions.getPosition() == 0)
>>>>> +      UseVMLx = false;
>>>>> }
>>>>> }
>>>>> 
>>>>> 
>>>>> 
>>>>> _______________________________________________
>>>>> llvm-commits mailing list
>>>>> llvm-commits at cs.uiuc.edu
>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>>> 
>>> 
>> 
>