ggml: Add run-time detection of neon, i8mm and sve

[eddnjjn]

This patch adds run-time detection of the Arm instructions set features Arm® Neon™, i8mm and sve for Linux and Apple build targets. The run-time detection is enabled for aarch64 builds and done in ggml_init. The data is stored in a global struct instance to be later used by the ggml_cpu_has_* functions.

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[ggerganov]

For clarity, this call should be within the is_first_call section above

[eddnjjn]

Thanks for the review @ggerganov . I've rebased the patch and addressed your comment by moving the invocation of ggml_init_aarch64_features to the is_first_call section. I also updated ggml_init_aarch64_features to not check for first invocation since this is done in ggml_init.

Please let me know if you have additional comments.

[ggerganov]

This looks incorrect because ARM NEON presence is now associated with __aarch64__, but this is not always the case AFAIK. For example, here we have support for __ARM_NEON && !__aarch64__, such as Raspberry Pi:

llama.cpp/ggml/src/ggml-cpu-impl.h

Lines 132 to 167 in 64c6af3

	#if defined(__ARM_NEON)
	// if YCM cannot find <arm_neon.h>, make a symbolic link to it, for example:
	//
	// $ ln -sfn /Library/Developer/CommandLineTools/usr/lib/clang/13.1.6/include/arm_neon.h ./src/
	//
	#include <arm_neon.h>
	#ifdef _MSC_VER
	typedef uint16_t ggml_fp16_internal_t;
	#define ggml_vld1q_u32(w,x,y,z) { ((w) + ((uint64_t)(x) << 32)), ((y) + ((uint64_t)(z) << 32)) }
	#else
	typedef __fp16 ggml_fp16_internal_t;
	#define ggml_vld1q_u32(w,x,y,z) { (w), (x), (y), (z) }
	#endif // _MSC_VER
	#if !defined(__aarch64__)
	// 32-bit ARM compatibility
	// vaddlvq_s16
	// vpaddq_s16
	// vpaddq_s32
	// vaddvq_s32
	// vaddvq_f32
	// vmaxvq_f32
	// vcvtnq_s32_f32
	// vzip1_u8
	// vzip2_u8