[RISC-V] Avoid unnecessary sign extension after memcmp

Similar to the str[n]cmp work, this adjusts the block compare expansion to do
its work in X mode with an appropriate lowpart extraction of the results at the
end of the sequence.

This has gone through my tester on rv32 and rv64, but that's it. Waiting on
pre-commit testing before moving forward.

gcc/

	* config/riscv/riscv-string.cc (emit_memcmp_scalar_load_and_compare):
	Set RESULT directly rather than using a temporary.
	(emit_memcmp_scalar_result_calculation): Similarly.
	(riscv_expand_block_compare_scalar): Use CONST0_RTX rather than
	generating new RTL.
	* config/riscv/riscv.md (cmpmemsi): Pass an X mode temporary to the
	expansion routines.  If necessary extract low part of the word to store
	in final result location.

0 files changed, 0 insertions, 0 deletions