[PATCH] AArch64: Enable subregister liveness tracking.

[Matthias Braun]

> On Mar 19, 2015, at 4:46 PM, Eric Christopher <echristo at gmail.com> wrote:
> 
> 
> 
> On Thu, Mar 19, 2015 at 4:33 PM Matthias Braun <matze at braunis.de <mailto:matze at braunis.de>> wrote:
> Hi t.p.northover, qcolombet,
> 
> Splitting this into an own commit to get some visibility.
> 
> After doing some extensive benchmarking wiht llvm test-suite, I see no correctness or compiletime changes. I see some very slight benchmark runtime improvements (which may or may not be noise). The only noticeable regression is in a benchmark were literally 6 lines of assembly changed for the better, so that must be cache issues.
> 
> REPOSITORY
>   rL LLVM
> 
> http://reviews.llvm.org/D8474 <http://reviews.llvm.org/D8474>
> 
> Files:
>   lib/Target/AArch64/AArch64Subtarget.h
> 
> Index: lib/Target/AArch64/AArch64Subtarget.h
> ===================================================================
> --- lib/Target/AArch64/AArch64Subtarget.h
> +++ lib/Target/AArch64/AArch64Subtarget.h
> @@ -91,6 +91,7 @@
>    bool enablePostMachineScheduler() const override {
>      return isCortexA53() || isCortexA57();
>    }
> +  bool enableSubRegLiveness() const override { return true; }
> 
> 
> Drive by feedback:
> 
> Most of AArch64 is option controlled for this sort of thing. Did you want to add an option with init(true) for this?
> 
> Personally no preference, but thought I'd bring it up.

In this case there is already the global -enable-subreg-liveness=false switch available, so I think there is no need for an additional aarch64 option.

- Matthias
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