вс, 15 сент. 2024 г. в 19:32, Georg-Johann Lay <a...@gjlay.de>: > > Unsigned comparisons may skip comparing the lower bytes when > the according bytes of the constant are all zeros. For example, > > uint16 >= 0x1200 > > is true iff > > hi8 (uint16) >= hi8 (0x1200) > > and similar for uint16 < 0x1200. Some comparisons against constants > that are an integral power of 256 where already handled in the split > preparation. That code has been outsourced to new avr_maybe_cmp_lsr() > which may change the operands such that the resulting insns become > a comparison of the high bytes against 0 plus a EQ / NE branch. > For example, > > uint32 >= 0x10000 > > can be rewritten as > > (uint32 >> 16) != 0. > > The according asm output is performed by new avr_out_cmp_lsr(). > > Ok for trunk?
Please apply. Denis. > > Johann > > -- > > gcc/ > * config/avr/avr-protos.h (avr_out_cmp_lsr, avr_maybe_cmp_lsr): New. > * config/avr/avr.cc (avr_maybe_cmp_lsr, avr_out_cmp_lsr): New > functions. > (avr_out_compare) [GEU, LTU]: Start output at byte CTZ(xval) / 8. > (avr_adjust_insn_length) [ADJUST_LEN_CMP_LSR]: Handle case. > * config/avr/avr.md (adjust_len) <cmp_lsr>: New attr value. > (*cmp<mode>_lsr): New define_insn_and_split. > (cbranch<mode>4_insn): When splitting, run avr_maybe_cmp_lsr() > which may map the operands to *cmp<mode>_lsr. > gcc/testsuite/ > * gcc.target/avr/torture/cmp-lsr-u16.c: New test. > * gcc.target/avr/torture/cmp-lsr-u24.c: New test. > * gcc.target/avr/torture/cmp-lsr-u32.c: New test. > * gcc.target/avr/torture/cmp-lsr-u64.c: New test.
