arm: Auto-vectorization for MVE: veor

arm: Auto-vectorization for MVE: veor

This patch enables MVE veorq instructions for auto-vectorization.  MVE
veorq insns in mve.md are modified to use xor instead of unspec
expression to support xor<mode>3.  The xor<mode>3 expander is added to
vec-common.md

2020-12-11  Christophe Lyon  <christophe.lyon@linaro.org>

	gcc/
	* config/arm/iterators.md (supf): Remove VEORQ_S and VEORQ_U.
	(VEORQ): Remove.
	* config/arm/mve.md (mve_veorq_u<mode>): New entry for veor
	instruction using expression xor.
	(mve_veorq_s<mode>): New expander.
	(mve_veorq_f<mode>): Use 'xor' code instead of unspec.
	* config/arm/neon.md (xor<mode>3): Renamed into xor<mode>3_neon.
	* config/arm/unspecs.md (VEORQ_S, VEORQ_U, VEORQ_F): Remove.
	* config/arm/vec-common.md (xor<mode>3): New expander.

	gcc/testsuite/
	* gcc.target/arm/simd/mve-veor.c: Add tests for veor.