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Cost Calculation on Loop Invariant on Arithmetic operations on RTL


Hello All:

I can see the Loop invariant pass in the GCC on RTL considering the register pressure and the cost manipulation
With respect to SET destination node in RTL.

The Loop invariant takes care of only address arithmetic candidates of Loop invariance.

In the function get_inv_cost, I can see the following check for the updation of comp_cost and the comp_cost
Gets incremented with respect all the dependence on the def node of the invariant variable.

If (!inv->cheap_address || inv-def->n_addr_uses < inv->def->n_uses)
  (*comp_cost += inv->cost + inv->eqno

Is there any specific reasons of addr_uses  less than the actual uses check for the address arithmetic candidate
Of Loop invariant. I think we should be aggressive enough and can do the cost calculation without this check.

One more point the above cost calculation should not be considering the register pressure_costs.

Thoughts Please ?

Thanks & Regards
Ajit


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