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

[Jim Grosbach]

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?

> 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;
>>>> }
>>>> }
>>>> 
>>>> 
>>>> 
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>> 
>