[PATCH] D32563: Add LiveRangeShrink pass to shrink live range within BB.

[Wei Mi via llvm-commits]

On Mon, May 1, 2017 at 4:52 PM, Matthias Braun via Phabricator
<reviews at reviews.llvm.org> wrote:
> MatzeB added a comment.
>
> In https://reviews.llvm.org/D32563#742848, @wmi wrote:
>
>> + Andy, for the history on pre-RA-sched and misched.
>
>
> pre-RA scheduling is deprecated it should only be concerned about bringing the SelectionDAG nodes into an order. The actual scheduling decisions should be done by the MachineScheduler nowadays.
>
> Is this pass necessary because the machine scheduler doesn't schedule instructions accross calls? Then https://reviews.llvm.org/D15667 may be related...
>

Thanks Matthias!

I tried the motivational testcase and changed most of the calls to
global variables. Reassociation generated similar result (containing
many live ranges interferences), and machine scheduler can do the live
range shrinking and removed all those interferences.

So it is likely because the machine scheduler doesn't schedule
instructions accross calls.

>
> https://reviews.llvm.org/D32563
>
>
>
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