[Bug target/63949] Aarch64 instruction combiner does not optimize subsi_sxth function as expected (gcc.target/aarch64/extend.c fails)

[vekumar at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63949

--- Comment #5 from vekumar at gcc dot gnu.org ---
Richard, what the function get_best_reg_extraction_insn is supposed to do in
make_extraction ?