Georg-Johann Lay <a...@gjlay.de> writes:
> There are occasions where knowledge about nonzero bits makes some
> optimizations possible. For example,
>
> Rd |= Rn << Off
>
> can be implemented as
>
> SBRC Rn, 0
> ORI Rd, 1 << Off
>
> when Rn in { 0, 1 }, i.e. nonzero_bits (Rn) == 1. This patch adds some
> patterns that exploit nonzero_bits() in some combiner patterns.
> As insn conditions are not supposed to contain nonzero_bits(), the patch
> splits such insns right after pass insn combine.
>
> The idea to split the patterns right after combine is from Jeff.
>
> The patch passes without new regressions. Ok for trunk?
Ok.
Please apply.
Denis
>
> Johann
>
> --
>
>
> AVR: target/119421 Better optimize some bit operations.
>
> There are occasions where knowledge about nonzero bits makes some
> optimizations possible. For example,
>
> Rd |= Rn << Off
>
> can be implemented as
>
> SBRC Rn, 0
> ORI Rd, 1 << Off
>
> when Rn in { 0, 1 }, i.e. nonzero_bits (Rn) == 1. This patch adds some
> patterns that exploit nonzero_bits() in some combiner patterns.
> As insn conditions are not supposed to contain nonzero_bits(), the patch
> splits such insns right after pass insn combine.
>
> PR target/119421
> gcc/
> * config/avr/avr.opt (-muse-nonzero-bits): New option.
> * config/avr/avr-protos.h (avr_nonzero_bits_lsr_operands_p): New.
> (make_avr_pass_split_nzb): New.
> * config/avr/avr.cc (avr_nonzero_bits_lsr_operands_p): New function.
> (avr_rtx_costs_1): Return costs for the new insns.
> * config/avr/avr.md (nzb): New insn attribute.
> (*nzb=1.<code>...): New insns to better support some bit
> operations for <code> in AND, IOR, XOR.
> * common/config/avr/avr-common.cc (avr_option_optimization_table):
> Enable -muse-nonzero-bits for -O2 and higher.
> * avr-passes.def (avr_pass_split_nzb): Insert pass atfer combine.
> * avr-passes.cc (avr_pass_data_split_nzb). New pass data.
> (avr_pass_split_nzb): New pass.
> (make_avr_pass_split_nzb): New function.
> * doc/invoke.texi (AVR Options): Document -muse-nonzero-bits.
> gcc/testsuite/
> * gcc.target/avr/torture/pr119421-sreg.c: New test.
