[llvm-dev] scheduler options documentation?

[Phil Tomson via llvm-dev]

As a follow on question: which of these options are already enabled when
compiling with -O3?

Phil

On Mon, Sep 12, 2016 at 10:37 AM, Phil Tomson <phil.a.tomson at gmail.com>
wrote:

> I see that there are several options to influence instruction scheduling,
> but there doesn't seem to be a lot of information about what they do, for
> example:
>
> -misched-topdown -misched-bottomup
>
> The description in MachineScheduler.cpp says:
>
> "Force top-down list scheduling" and "Force bottom-up list scheduling"
>
> Which isn't too helpful - where might I want to use these? Under what
> conditions might they improve an instruction schedule?
>
> Similar questions for the instruction scheduler strategies:
>
> -misched=(default, converge,
> ilpmax, ilpmin, or shuffle)
>
> And for the analysis heuristics:
>
> -misched-cluster,
> -misched-cyclicpath, -misched-regpressure, and -misched-
> fusion
>
> Are these things mutually exclusive or can they be combined? What
> combination will give the most rigorous analysis and improve scheduling (at
> the cost of longer runtime of llc)
>
> Phil
>
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