[llvm-dev] scheduler options documentation?

[Phil Tomson via llvm-dev]

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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