I have made the following changes in the estimate_reg_pressure_cost function used by the loop invariant and IVOPTS.
Earlier the estimate_reg_pressure cost uses the cost of n_new variables that
are generated by the Loop Invariant
and IVOPTS. These are not sufficient for register pressure calculation. The
register pressure cost calculation should
use the n_new + n_old (numbers) to consider the cost. n_old is the register
used inside the loops and the effect of
n_new new variables generated by loop invariant and IVOPTS on register
pressure is based on how the new
variables impact on register used inside the loops. The increase or decrease in
register pressure is due to the impact
of new variables on the register used inside the loops. The register-register
move cost or the spill cost should consider
the cost associated with register used and the new variables generated. The
movement of new variables increases or
decreases the register pressure, which is based on overall cost of n_new +
n_old variables.
The increase and decrease in register pressure is based on the overall cost of
n_new + n_old as the changes in the
register pressure caused due to new variables is based on how the changes
behave with respect to the register used
in the loops.
Thus the register pressure caused to new variables is based on the new
variables and its impact on register used inside
the loops and thus consider the overall cost of n_new + n_old.
Bootstrap for i386 and reg tested on i386 with the change is fine.
SPEC CPU 2000 benchmarks are run and there is following impact on the
performance
and code size.
ratio with the optimization vs ratio without optimization for INT benchmarks
(3807.632 vs 3804.661)
ratio with the optimization vs ratio without optimization for FP benchmarks
( 4668.743 vs 4778.741)
Code size reduction with respect to FP SPEC CPU 2000 benchmarks
Number of instruction with optimization = 1094117
Number of instruction without optimization = 1094659
Reduction in number of instruction with the optimization = 542 instruction.
[Patch,optimization]: Optimized changes in the estimate
register pressure cost.
Earlier the estimate_reg_pressure cost uses the cost of n_new variables that
are generated by the Loop Invariant and IVOPTS. These are not sufficient for
register pressure calculation. The register pressure cost calculation should
use the n_new + n_old (numbers) to consider the cost. n_old is the register
used inside the loops and the affect of n_new new variables generated by
loop invariant and IVOPTS on register pressure is based on how the new
variables impact on register used inside the loops.
ChangeLog:
2015-09-26 Ajit Agarwal <ajit...@xilinx.com>
* cfgloopanal.c (estimate_reg_pressure_cost) : Add changes
to consider the n_new plus n_old in the register pressure
cost.
Signed-off-by:Ajit Agarwal ajit...@xilinx.com
Thanks & Regards
Ajit
0001-Patch-optimization-Optimized-changes-in-the-estimate.patch
Description: 0001-Patch-optimization-Optimized-changes-in-the-estimate.patch
