[PATCH] D10416: Use function attribute "arm-restrict-it"

[Eric Christopher]

echristo added a reviewer: grosbach.

In http://reviews.llvm.org/D10416#198657, @ahatanak wrote:

> Are you suggesting adding FeatureRestrictedIT to the implied feature list of HasV8Ops? I thought about doing so but found out it would make it impossible to disable restrict-it when we target v8. Try compiling the following IR with -mattr=-restrict-it after adding FeatureRestrictedIT to the implied feature list:


Fascinating.

> This fails because disabling restrict-it transitively disables HasV8Ops too (see function ClearImpliedBits in SubtargetFeature.cpp).


Right.

> If I compile the IR with trunk's llc with command line option -arm-no-restrict-it, it compiles without any errors.

> 

> $ llc f1.ll -o - -arm-no-restrict-it

> 

> Do we need the capability to turn off disable restrict-it when targeting armv8? I was assuming we do need it although I wasn't sure why users would want to do that.


I don't know. I wouldn't think so tbh which is why I just suggested putting it as a feature on the subarchitecture.

Jim?

-eric


http://reviews.llvm.org/D10416