Use ARM Advanced SIMD (NEON) intrinsics where available

NEON support is required on the Aarch64 architecture for standard
implementations. Hardware designers for specialized markets can choose
not to support it, but that's true of floating point as well, which
we assume is supported. As with x86, some SIMD support is available
on 32-bit platforms, but those are not interesting from a performance
standpoint and would require an inconvenient runtime check.

Nathan Bossart

Reviewed by John Naylor, Andres Freund, Thomas Munro, and Tom Lane
Discussion: https://www.postgresql.org/message-id/flat/CAFBsxsEyR9JkfbPcDXBRYEfdfC__OkwVGdwEAgY4Rv0cvw35EA%40mail.gmail.com#aba7a64b11503494ffd8dd27067626a9

Author: j-naylor

src/include/port/simd.h

@@ -33,6 +33,20 @@
 typedef __m128i Vector8;
 typedef __m128i Vector32;
 
+#elif defined(__aarch64__) && defined(__ARM_NEON)
+/*
+ * We use the Neon instructions if the compiler provides access to them (as
+ * indicated by __ARM_NEON) and we are on aarch64.  While Neon support is
+ * technically optional for aarch64, it appears that all available 64-bit
+ * hardware does have it.  Neon exists in some 32-bit hardware too, but we
+ * could not realistically use it there without a run-time check, which seems
+ * not worth the trouble for now.
+ */
+#include <arm_neon.h>
+#define USE_NEON
+typedef uint8x16_t Vector8;
+typedef uint32x4_t Vector32;
+
 #else
 /*
  * If no SIMD instructions are available, we can in some cases emulate vector
@@ -90,6 +104,8 @@ vector8_load(Vector8 *v, const uint8 *s)
 {
 #if defined(USE_SSE2)
 	*v = _mm_loadu_si128((const __m128i *) s);
+#elif defined(USE_NEON)
+	*v = vld1q_u8(s);
 #else
 	memcpy(v, s, sizeof(Vector8));
 #endif
@@ -101,6 +117,8 @@ vector32_load(Vector32 *v, const uint32 *s)
 {
 #ifdef USE_SSE2
 	*v = _mm_loadu_si128((const __m128i *) s);
+#elif defined(USE_NEON)
+	*v = vld1q_u32(s);
 #endif
 }
 #endif							/* ! USE_NO_SIMD */
@@ -113,6 +131,8 @@ vector8_broadcast(const uint8 c)
 {
 #if defined(USE_SSE2)
 	return _mm_set1_epi8(c);
+#elif defined(USE_NEON)
+	return vdupq_n_u8(c);
 #else
 	return ~UINT64CONST(0) / 0xFF * c;
 #endif
@@ -124,6 +144,8 @@ vector32_broadcast(const uint32 c)
 {
 #ifdef USE_SSE2
 	return _mm_set1_epi32(c);
+#elif defined(USE_NEON)
+	return vdupq_n_u32(c);
 #endif
 }
 #endif							/* ! USE_NO_SIMD */
@@ -153,7 +175,7 @@ vector8_has(const Vector8 v, const uint8 c)
 #if defined(USE_NO_SIMD)
 	/* any bytes in v equal to c will evaluate to zero via XOR */
 	result = vector8_has_zero(v ^ vector8_broadcast(c));
-#elif defined(USE_SSE2)
+#else
 	result = vector8_is_highbit_set(vector8_eq(v, vector8_broadcast(c)));
 #endif
 
@@ -173,7 +195,7 @@ vector8_has_zero(const Vector8 v)
 	 * circular definition.
 	 */
 	return vector8_has_le(v, 0);
-#elif defined(USE_SSE2)
+#else
 	return vector8_has(v, 0);
 #endif
 }
@@ -223,7 +245,7 @@ vector8_has_le(const Vector8 v, const uint8 c)
 			}
 		}
 	}
-#elif defined(USE_SSE2)
+#else
 
 	/*
 	 * Use saturating subtraction to find bytes <= c, which will present as
@@ -245,6 +267,8 @@ vector8_is_highbit_set(const Vector8 v)
 {
 #ifdef USE_SSE2
 	return _mm_movemask_epi8(v) != 0;
+#elif defined(USE_NEON)
+	return vmaxvq_u8(v) > 0x7F;
 #else
 	return v & vector8_broadcast(0x80);
 #endif
@@ -258,6 +282,8 @@ vector8_or(const Vector8 v1, const Vector8 v2)
 {
 #ifdef USE_SSE2
 	return _mm_or_si128(v1, v2);
+#elif defined(USE_NEON)
+	return vorrq_u8(v1, v2);
 #else
 	return v1 | v2;
 #endif
@@ -269,6 +295,8 @@ vector32_or(const Vector32 v1, const Vector32 v2)
 {
 #ifdef USE_SSE2
 	return _mm_or_si128(v1, v2);
+#elif defined(USE_NEON)
+	return vorrq_u32(v1, v2);
 #endif
 }
 #endif							/* ! USE_NO_SIMD */
@@ -285,6 +313,8 @@ vector8_ssub(const Vector8 v1, const Vector8 v2)
 {
 #ifdef USE_SSE2
 	return _mm_subs_epu8(v1, v2);
+#elif defined(USE_NEON)
+	return vqsubq_u8(v1, v2);
 #endif
 }
 #endif							/* ! USE_NO_SIMD */
@@ -299,6 +329,8 @@ vector8_eq(const Vector8 v1, const Vector8 v2)
 {
 #ifdef USE_SSE2
 	return _mm_cmpeq_epi8(v1, v2);
+#elif defined(USE_NEON)
+	return vceqq_u8(v1, v2);
 #endif
 }
 #endif							/* ! USE_NO_SIMD */
@@ -309,6 +341,8 @@ vector32_eq(const Vector32 v1, const Vector32 v2)
 {
 #ifdef USE_SSE2
 	return _mm_cmpeq_epi32(v1, v2);
+#elif defined(USE_NEON)
+	return vceqq_u32(v1, v2);
 #endif
 }
 #endif							/* ! USE_NO_SIMD */