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

[segher at gcc dot gnu.org]

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

Segher Boessenkool <segher at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |segher at gcc dot gnu.org

--- Comment #9 from Segher Boessenkool <segher at gcc dot gnu.org> ---
A MULT by a constant power of 2 is not canonical RTL (well, not what
simplify_rtx would give you); combine shouldn't generate this.