[PATCH] D10414: Attach function attribute "arm-restrict-it" instead of passing arm-restrict-it as a backend-option

[Jim Grosbach via cfe-commits]

> On Sep 10, 2015, at 1:24 AM, James Molloy <james.molloy at arm.com> wrote:
> 
> jmolloy added a subscriber: jmolloy.
> jmolloy added a comment.
> 
> Hi Akira,
> 
> I'm sorry to be contrary (and I missed the discussion on Tuesday because I was away on vacation) but I think there *is* a usecase for -mno-restrict-it to work, and I would hate to see it broken.
> 
> Non-restricted IT blocks are indeed deprecated for ARMv8 in the ARMARM. But there are circumstances where you may still want to emit them - the biggest example being you're compiling for a CPU microarchitecture that you *know* doesn't have a performance penalty on non-restricted IT blocks. Restricted IT blocks can pessimize code quite badly in some circumstances, and allowing people to turn it off for their target if needed is very important, IMO.

If such microarchitectures exist, shouldn’t they be represented properly as a CPU in the backend and get the right setting by default?




> 
> Cheers,
> 
> James
> 
> 
> http://reviews.llvm.org/D10414
> 
> 
>