Re: [PATCH] rs6000: Parameterize some const values for density test

[Segher Boessenkool <segher@kernel.crashing.org>]

Hi!

On Fri, Sep 17, 2021 at 11:27:09AM -0500, Bill Schmidt wrote:
> On 9/15/21 3:52 AM, Kewen.Lin wrote:
> >+-param=rs6000-density-pct-threshold=
> >+Target Undocumented Joined UInteger Var(rs6000_density_pct_threshold) 
> >Init(85) IntegerRange(0, 99) Param
> >+When costing for loop vectorization, we probably need to penalize the 
> >loop body cost if the existing cost model may not adequately reflect 
> >delays from unavailable vector resources.  We collect the cost for 
> >vectorized statements and non-vectorized statements separately, check the 
> >proportion of vec_cost to total cost of vec_cost and non vec_cost, and 
> >penalize only if the proportion exceeds the threshold specified by this 
> >parameter.  The default value is 85.
> >+
> >+-param=rs6000-density-size-threshold=
> >+Target Undocumented Joined UInteger Var(rs6000_density_size_threshold) 
> >Init(70) IntegerRange(0, 99) Param
> 
> I think 99 is not a sufficient upper bound.  This is a counting value 
> that could in theory get much higher.  Can you set it to something 
> ridiculous like IntegerRange(0, 1000)?

It is a percentage.  (0,100) is the maximum that makes any sense :-)

It may be useful to make it a bit more sensitive than hundreds, but it
is a heuristic anyway, this will work fine.

But allowing 100 will be good.


Segher