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

[pinskia at gcc dot gnu.org]

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

--- Comment #11 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
https://gcc.gnu.org/ml/gcc-patches/2015-01/msg01020.html