arm: ACLE I8MM multiply-accumulate

arm: ACLE I8MM multiply-accumulate

This patch adds intrinsics for matrix multiply-accumulate instructions
including vmmlaq_s32, vmmlaq_u32, and vusmmlaq_s32.

gcc/ChangeLog:

2020-02-21  Dennis Zhang  <dennis.zhang@arm.com>

	* config/arm/arm_neon.h (vmmlaq_s32, vmmlaq_u32, vusmmlaq_s32): New.
	* config/arm/arm_neon_builtins.def (smmla, ummla, usmmla): New.
	* config/arm/iterators.md (MATMUL): New iterator.
	(sup): Add UNSPEC_MATMUL_S, UNSPEC_MATMUL_U, and UNSPEC_MATMUL_US.
	(mmla_sfx): New attribute.
	* config/arm/neon.md (neon_<sup>mmlav16qi): New.
	* config/arm/unspecs.md (UNSPEC_MATMUL_S, UNSPEC_MATMUL_U): New.
	(UNSPEC_MATMUL_US): New.

gcc/testsuite/ChangeLog:

2020-02-21  Dennis Zhang  <dennis.zhang@arm.com>

	* gcc.target/arm/simd/vmmla_1.c: New test.