[PATCH PR90240][RFC]Avoid scaling cost overflow by introducing scaling bound

[bin.cheng]

Hi,

This is the draft patch avoiding scaling cost overflow by introducing a scaling bound
in IVOPTs.  For now the bound is 20, and scaling factor will be further scaled wrto
this bound.  For example, scaling factor like 1, 1000, 2000(max) would be scaled to
1, 10, 20 correspondingly.

HI Martin, I remember you introduced comp_cost/cost_scaling to improve one case
in spec2017.  Unfortunately I don't have access to the benchmark now, could you help
verify that if this patch has performance issue on it please?  Thanks

Bootstrap and test on x86_64, and this is for further comment/discussion.

Thanks,
bin
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