diff --git a/src/include/port/pg_lfind.h b/src/include/port/pg_lfind.h index a4e13dffec..d575e733d3 100644 --- a/src/include/port/pg_lfind.h +++ b/src/include/port/pg_lfind.h @@ -91,16 +91,19 @@ pg_lfind32(uint32 key, uint32 *base, uint32 nelem) { uint32 i = 0; -#ifdef USE_SSE2 +#ifndef USE_NO_SIMD /* - * A 16-byte register only has four 4-byte lanes. For better - * instruction-level parallelism, each loop iteration operates on a block - * of four registers. Testing has showed this is ~40% faster than using a - * block of two registers. + * For better instruction-level parallelism, each loop iteration operates + * on a block of four registers. Testing for SSE2 has showed this is ~40% + * faster than using a block of two registers. */ - const __m128i keys = _mm_set1_epi32(key); /* load 4 copies of key */ - uint32 iterations = nelem & ~0xF; /* round down to multiple of 16 */ + const Vector32 keys = vector32_broadcast(key); /* load copies of key */ + const uint32 nelem_per_vector = sizeof(Vector32) / sizeof(uint32); + const uint32 nelem_per_iteration = 4 * nelem_per_vector; + + /* round down to multiple of elements per iteration */ + const uint32 tail_idx = nelem & ~(nelem_per_iteration - 1); #if defined(USE_ASSERT_CHECKING) bool assert_result = false; @@ -116,49 +119,59 @@ pg_lfind32(uint32 key, uint32 *base, uint32 nelem) } #endif - for (i = 0; i < iterations; i += 16) + for (i = 0; i < tail_idx; i += nelem_per_iteration) { - /* load the next block into 4 registers holding 4 values each */ - const __m128i vals1 = _mm_loadu_si128((__m128i *) & base[i]); - const __m128i vals2 = _mm_loadu_si128((__m128i *) & base[i + 4]); - const __m128i vals3 = _mm_loadu_si128((__m128i *) & base[i + 8]); - const __m128i vals4 = _mm_loadu_si128((__m128i *) & base[i + 12]); + Vector32 vals1, + vals2, + vals3, + vals4, + result1, + result2, + result3, + result4, + tmp1, + tmp2, + result; + + /* load the next block into 4 registers */ + vector32_load(&vals1, &base[i]); + vector32_load(&vals2, &base[i + nelem_per_vector]); + vector32_load(&vals3, &base[i + nelem_per_vector * 2]); + vector32_load(&vals4, &base[i + nelem_per_vector * 3]); /* compare each value to the key */ - const __m128i result1 = _mm_cmpeq_epi32(keys, vals1); - const __m128i result2 = _mm_cmpeq_epi32(keys, vals2); - const __m128i result3 = _mm_cmpeq_epi32(keys, vals3); - const __m128i result4 = _mm_cmpeq_epi32(keys, vals4); + result1 = vector32_eq(keys, vals1); + result2 = vector32_eq(keys, vals2); + result3 = vector32_eq(keys, vals3); + result4 = vector32_eq(keys, vals4); /* combine the results into a single variable */ - const __m128i tmp1 = _mm_or_si128(result1, result2); - const __m128i tmp2 = _mm_or_si128(result3, result4); - const __m128i result = _mm_or_si128(tmp1, tmp2); + tmp1 = vector32_or(result1, result2); + tmp2 = vector32_or(result3, result4); + result = vector32_or(tmp1, tmp2); /* see if there was a match */ - if (_mm_movemask_epi8(result) != 0) + if (vector8_is_highbit_set((Vector8) result)) { -#if defined(USE_ASSERT_CHECKING) Assert(assert_result == true); -#endif return true; } } -#endif /* USE_SSE2 */ +#endif /* ! USE_NO_SIMD */ /* Process the remaining elements one at a time. */ for (; i < nelem; i++) { if (key == base[i]) { -#if defined(USE_SSE2) && defined(USE_ASSERT_CHECKING) +#ifndef USE_NO_SIMD Assert(assert_result == true); #endif return true; } } -#if defined(USE_SSE2) && defined(USE_ASSERT_CHECKING) +#ifndef USE_NO_SIMD Assert(assert_result == false); #endif return false; diff --git a/src/include/port/simd.h b/src/include/port/simd.h index a425cd887b..b508d47b12 100644 --- a/src/include/port/simd.h +++ b/src/include/port/simd.h @@ -31,22 +31,32 @@ #include #define USE_SSE2 typedef __m128i Vector8; +typedef __m128i Vector32; #else /* * If no SIMD instructions are available, we can in some cases emulate vector - * operations using bitwise operations on unsigned integers. + * operations using bitwise operations on unsigned integers. Note that many + * of the functions in this file presently do not have non-SIMD + * implementations. In particular, none of the functions involving Vector32 + * are implemented without SIMD since it's likely not worthwhile to represent + * two 32-bit integers using a uint64. */ #define USE_NO_SIMD typedef uint64 Vector8; #endif - /* load/store operations */ static inline void vector8_load(Vector8 *v, const uint8 *s); +#ifndef USE_NO_SIMD +static inline void vector32_load(Vector32 *v, const uint32 *s); +#endif /* assignment operations */ static inline Vector8 vector8_broadcast(const uint8 c); +#ifndef USE_NO_SIMD +static inline Vector32 vector32_broadcast(const uint32 c); +#endif /* element-wise comparisons to a scalar */ static inline bool vector8_has(const Vector8 v, const uint8 c); @@ -56,14 +66,21 @@ static inline bool vector8_is_highbit_set(const Vector8 v); /* arithmetic operations */ static inline Vector8 vector8_or(const Vector8 v1, const Vector8 v2); - -/* Different semantics for SIMD architectures. */ #ifndef USE_NO_SIMD +static inline Vector32 vector32_or(const Vector32 v1, const Vector32 v2); +static inline Vector8 vector8_ssub(const Vector8 v1, const Vector8 v2); +#endif -/* comparisons between vectors */ +/* + * comparisons between vectors + * + * Note: These return a vector rather than booloan, which is why we don't + * have non-SIMD implementations. + */ +#ifndef USE_NO_SIMD static inline Vector8 vector8_eq(const Vector8 v1, const Vector8 v2); - -#endif /* ! USE_NO_SIMD */ +static inline Vector32 vector32_eq(const Vector32 v1, const Vector32 v2); +#endif /* * Load a chunk of memory into the given vector. @@ -78,6 +95,15 @@ vector8_load(Vector8 *v, const uint8 *s) #endif } +#ifndef USE_NO_SIMD +static inline void +vector32_load(Vector32 *v, const uint32 *s) +{ +#ifdef USE_SSE2 + *v = _mm_loadu_si128((const __m128i *) s); +#endif +} +#endif /* ! USE_NO_SIMD */ /* * Create a vector with all elements set to the same value. @@ -92,6 +118,16 @@ vector8_broadcast(const uint8 c) #endif } +#ifndef USE_NO_SIMD +static inline Vector32 +vector32_broadcast(const uint32 c) +{ +#ifdef USE_SSE2 + return _mm_set1_epi32(c); +#endif +} +#endif /* ! USE_NO_SIMD */ + /* * Return true if any elements in the vector are equal to the given scalar. */ @@ -118,7 +154,7 @@ vector8_has(const Vector8 v, const uint8 c) /* 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) - result = _mm_movemask_epi8(_mm_cmpeq_epi8(v, vector8_broadcast(c))); + result = vector8_is_highbit_set(vector8_eq(v, vector8_broadcast(c))); #endif Assert(assert_result == result); @@ -133,8 +169,8 @@ vector8_has_zero(const Vector8 v) { #if defined(USE_NO_SIMD) /* - * We cannot call vector8_has() here, because that would lead to a circular - * definition. + * We cannot call vector8_has() here, because that would lead to a + * circular definition. */ return vector8_has_le(v, 0); #elif defined(USE_SSE2) @@ -150,9 +186,6 @@ static inline bool vector8_has_le(const Vector8 v, const uint8 c) { bool result = false; -#if defined(USE_SSE2) - __m128i sub; -#endif /* pre-compute the result for assert checking */ #ifdef USE_ASSERT_CHECKING @@ -194,10 +227,10 @@ vector8_has_le(const Vector8 v, const uint8 c) /* * Use saturating subtraction to find bytes <= c, which will present as - * NUL bytes in 'sub'. + * NUL bytes. This approach is a workaround for the lack of unsigned + * comparison instructions on some architectures. */ - sub = _mm_subs_epu8(v, vector8_broadcast(c)); - result = vector8_has_zero(sub); + result = vector8_has_zero(vector8_ssub(v, vector8_broadcast(c))); #endif Assert(assert_result == result); @@ -230,14 +263,37 @@ vector8_or(const Vector8 v1, const Vector8 v2) #endif } - -/* Different semantics for SIMD architectures. */ #ifndef USE_NO_SIMD +static inline Vector32 +vector32_or(const Vector32 v1, const Vector32 v2) +{ +#ifdef USE_SSE2 + return _mm_or_si128(v1, v2); +#endif +} +#endif /* ! USE_NO_SIMD */ + +/* + * Return the result of subtracting the respective elements of the input + * vectors using saturation (i.e., if the operation would yield a value less + * than zero, zero is returned instead). For more information on saturation + * arithmetic, see https://en.wikipedia.org/wiki/Saturation_arithmetic + */ +#ifndef USE_NO_SIMD +static inline Vector8 +vector8_ssub(const Vector8 v1, const Vector8 v2) +{ +#ifdef USE_SSE2 + return _mm_subs_epu8(v1, v2); +#endif +} +#endif /* ! USE_NO_SIMD */ /* * Return a vector with all bits set in each lane where the the corresponding * lanes in the inputs are equal. */ +#ifndef USE_NO_SIMD static inline Vector8 vector8_eq(const Vector8 v1, const Vector8 v2) { @@ -245,7 +301,16 @@ vector8_eq(const Vector8 v1, const Vector8 v2) return _mm_cmpeq_epi8(v1, v2); #endif } +#endif /* ! USE_NO_SIMD */ +#ifndef USE_NO_SIMD +static inline Vector32 +vector32_eq(const Vector32 v1, const Vector32 v2) +{ +#ifdef USE_SSE2 + return _mm_cmpeq_epi32(v1, v2); +#endif +} #endif /* ! USE_NO_SIMD */ #endif /* SIMD_H */