PR 117048: simplify-rtx: Extend (x << C1) | (X >> C2) --> ROTATE transformation to...

PR 117048: simplify-rtx: Extend (x << C1) | (X >> C2) --> ROTATE transformation to vector operands

In the testcase from patch [2/2] we want to match a vector rotate operate from
an IOR of left and right shifts by immediate.  simplify-rtx has code for just
that but it looks like it's prepared to do handle only scalar operands.
In practice most of the code works for vector modes as well except the shift
amounts are checked to be CONST_INT rather than vector constants that we have
here.  This is easily extended by using unwrap_const_vec_duplicate to extract
the repeating constant shift amount.  With this change combine now tries
matching the simpler and expected:
(set (reg:V2DI 119 [ _14 ])
    (rotate:V2DI (xor:V2DI (reg:V2DI 114 [ vect__1.12_16 ])
            (reg:V2DI 116 [ *m1_01_8(D) ]))
        (const_vector:V2DI [
                (const_int 32 [0x20]) repeated x2
            ])))
instead of the previous:
(set (reg:V2DI 119 [ _14 ])
    (ior:V2DI (ashift:V2DI (xor:V2DI (reg:V2DI 114 [ vect__1.12_16 ])
                (reg:V2DI 116 [ *m1_01_8(D) ]))
            (const_vector:V2DI [
                    (const_int 32 [0x20]) repeated x2
                ]))
        (lshiftrt:V2DI (xor:V2DI (reg:V2DI 114 [ vect__1.12_16 ])
                (reg:V2DI 116 [ *m1_01_8(D) ]))
            (const_vector:V2DI [
                    (const_int 32 [0x20]) repeated x2
                ]))))

To actually fix the PR the aarch64 backend needs some adjustment as well
which is done in patch [2/2], which adds the testcase as well.

Bootstrapped and tested on aarch64-none-linux-gnu.

Signed-off-by: Kyrylo Tkachov <ktkachov@nvidia.com>
	PR target/117048
	* simplify-rtx.cc (simplify_context::simplify_binary_operation_1):
	Handle vector constants in (x << C1) | (x >> C2) -> ROTATE
	simplification.