Hi, Why can't we replace function force_expr_to_var_cost directly with function computation_cost in tree-ssa-loop-ivopt.c?
Actually I think it is inaccurate for the current recursive algorithm in force_expr_to_var_cost to estimate expr cost. Instead computation_cost can count some back-end factors and make the estimation more accurate. For example, using computation_cost, we may check whether back-ends can tie some modes transformation expressed by SUBREG or not. If we use force_expr_to_var_cost, some more computations around type promotion/demotion would increase the cost estimated. Looking at the algorithm in force_expr_to_var_cost, it is just to analyze the operator in the expression and give estimation. Should it be the same as expanding EXPR to RTX and give estimation like in computation_cost? Any thoughts? Thanks, -Jiangning
