/*-------------------------------------------------------------------------
*
* pg_lfind.h
- * Optimized linear search routines.
+ * Optimized linear search routines using SIMD intrinsics where
+ * available.
*
* Copyright (c) 2022, PostgreSQL Global Development Group
*
#include "port/simd.h"
+/*
+ * pg_lfind8
+ *
+ * Return true if there is an element in 'base' that equals 'key', otherwise
+ * return false.
+ */
+static inline bool
+pg_lfind8(uint8 key, uint8 *base, uint32 nelem)
+{
+ uint32 i;
+
+ /* round down to multiple of vector length */
+ uint32 tail_idx = nelem & ~(sizeof(Vector8) - 1);
+ Vector8 chunk;
+
+ for (i = 0; i < tail_idx; i += sizeof(Vector8))
+ {
+ vector8_load(&chunk, &base[i]);
+ if (vector8_has(chunk, key))
+ return true;
+ }
+
+ /* Process the remaining elements one at a time. */
+ for (; i < nelem; i++)
+ {
+ if (key == base[i])
+ return true;
+ }
+
+ return false;
+}
+
+/*
+ * pg_lfind8_le
+ *
+ * Return true if there is an element in 'base' that is less than or equal to
+ * 'key', otherwise return false.
+ */
+static inline bool
+pg_lfind8_le(uint8 key, uint8 *base, uint32 nelem)
+{
+ uint32 i;
+
+ /* round down to multiple of vector length */
+ uint32 tail_idx = nelem & ~(sizeof(Vector8) - 1);
+ Vector8 chunk;
+
+ for (i = 0; i < tail_idx; i += sizeof(Vector8))
+ {
+ vector8_load(&chunk, &base[i]);
+ if (vector8_has_le(chunk, key))
+ return true;
+ }
+
+ /* Process the remaining elements one at a time. */
+ for (; i < nelem; i++)
+ {
+ if (base[i] <= key)
+ return true;
+ }
+
+ return false;
+}
+
/*
* pg_lfind32
*
{
uint32 i = 0;
- /* Use SIMD intrinsics where available. */
#ifdef USE_SSE2
/*
*
* src/include/port/simd.h
*
+ * NOTES
+ * - VectorN in this file refers to a register where the element operands
+ * are N bits wide. The vector width is platform-specific, so users that care
+ * about that will need to inspect "sizeof(VectorN)".
+ *
*-------------------------------------------------------------------------
*/
#ifndef SIMD_H
#define SIMD_H
+#if (defined(__x86_64__) || defined(_M_AMD64))
/*
* SSE2 instructions are part of the spec for the 64-bit x86 ISA. We assume
* that compilers targeting this architecture understand SSE2 intrinsics.
* will allow the use of intrinsics that haven't been enabled at compile
* time.
*/
-#if (defined(__x86_64__) || defined(_M_AMD64))
#include <emmintrin.h>
#define USE_SSE2
+typedef __m128i Vector8;
+
+#else
+/*
+ * If no SIMD instructions are available, we can in some cases emulate vector
+ * operations using bitwise operations on unsigned integers.
+ */
+#define USE_NO_SIMD
+typedef uint64 Vector8;
+#endif
+
+
+/* load/store operations */
+static inline void vector8_load(Vector8 *v, const uint8 *s);
+
+/* assignment operations */
+static inline Vector8 vector8_broadcast(const uint8 c);
+
+/* element-wise comparisons to a scalar */
+static inline bool vector8_has(const Vector8 v, const uint8 c);
+static inline bool vector8_has_zero(const Vector8 v);
+static inline bool vector8_has_le(const Vector8 v, const uint8 c);
+
+
+/*
+ * Load a chunk of memory into the given vector.
+ */
+static inline void
+vector8_load(Vector8 *v, const uint8 *s)
+{
+#if defined(USE_SSE2)
+ *v = _mm_loadu_si128((const __m128i *) s);
+#else
+ memcpy(v, s, sizeof(Vector8));
#endif
+}
+
+
+/*
+ * Create a vector with all elements set to the same value.
+ */
+static inline Vector8
+vector8_broadcast(const uint8 c)
+{
+#if defined(USE_SSE2)
+ return _mm_set1_epi8(c);
+#else
+ return ~UINT64CONST(0) / 0xFF * c;
+#endif
+}
+
+/*
+ * Return true if any elements in the vector are equal to the given scalar.
+ */
+static inline bool
+vector8_has(const Vector8 v, const uint8 c)
+{
+ bool result;
+
+ /* pre-compute the result for assert checking */
+#ifdef USE_ASSERT_CHECKING
+ bool assert_result = false;
+
+ for (int i = 0; i < sizeof(Vector8); i++)
+ {
+ if (((const uint8 *) &v)[i] == c)
+ {
+ assert_result = true;
+ break;
+ }
+ }
+#endif /* USE_ASSERT_CHECKING */
+
+#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)
+ result = _mm_movemask_epi8(_mm_cmpeq_epi8(v, vector8_broadcast(c)));
+#endif
+
+ Assert(assert_result == result);
+ return result;
+}
+
+/*
+ * Convenience function equivalent to vector8_has(v, 0)
+ */
+static inline bool
+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.
+ */
+ return vector8_has_le(v, 0);
+#elif defined(USE_SSE2)
+ return vector8_has(v, 0);
+#endif
+}
+
+/*
+ * Return true if any elements in the vector are less than or equal to the
+ * given scalar.
+ */
+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
+ bool assert_result = false;
+
+ for (int i = 0; i < sizeof(Vector8); i++)
+ {
+ if (((const uint8 *) &v)[i] <= c)
+ {
+ assert_result = true;
+ break;
+ }
+ }
+#endif /* USE_ASSERT_CHECKING */
+
+#if defined(USE_NO_SIMD)
+
+ /*
+ * To find bytes <= c, we can use bitwise operations to find bytes < c+1,
+ * but it only works if c+1 <= 128 and if the highest bit in v is not set.
+ * Adapted from
+ * https://graphics.stanford.edu/~seander/bithacks.html#HasLessInWord
+ */
+ if ((int64) v >= 0 && c < 0x80)
+ result = (v - vector8_broadcast(c + 1)) & ~v & vector8_broadcast(0x80);
+ else
+ {
+ /* one byte at a time */
+ for (int i = 0; i < sizeof(Vector8); i++)
+ {
+ if (((const uint8 *) &v)[i] <= c)
+ {
+ result = true;
+ break;
+ }
+ }
+ }
+#elif defined(USE_SSE2)
+
+ /*
+ * Use saturating subtraction to find bytes <= c, which will present as
+ * NUL bytes in 'sub'.
+ */
+ sub = _mm_subs_epu8(v, vector8_broadcast(c));
+ result = vector8_has_zero(sub);
+#endif
+
+ Assert(assert_result == result);
+ return result;
+}
#endif /* SIMD_H */
-- the operations complete without crashing or hanging and that none of their
-- internal sanity tests fail.
--
-SELECT test_lfind();
- test_lfind
-------------
+SELECT test_lfind8();
+ test_lfind8
+-------------
+
+(1 row)
+
+SELECT test_lfind8_le();
+ test_lfind8_le
+----------------
+
+(1 row)
+
+SELECT test_lfind32();
+ test_lfind32
+--------------
(1 row)
-- the operations complete without crashing or hanging and that none of their
-- internal sanity tests fail.
--
-SELECT test_lfind();
+SELECT test_lfind8();
+SELECT test_lfind8_le();
+SELECT test_lfind32();
-- complain if script is sourced in psql, rather than via CREATE EXTENSION
\echo Use "CREATE EXTENSION test_lfind" to load this file. \quit
-CREATE FUNCTION test_lfind()
+CREATE FUNCTION test_lfind32()
+ RETURNS pg_catalog.void
+ AS 'MODULE_PATHNAME' LANGUAGE C;
+
+CREATE FUNCTION test_lfind8()
+ RETURNS pg_catalog.void
+ AS 'MODULE_PATHNAME' LANGUAGE C;
+
+CREATE FUNCTION test_lfind8_le()
RETURNS pg_catalog.void
AS 'MODULE_PATHNAME' LANGUAGE C;
#include "fmgr.h"
#include "port/pg_lfind.h"
+/*
+ * Convenience macros for testing both vector and scalar operations. The 2x
+ * factor is to make sure iteration works
+ */
+#define LEN_NO_TAIL(vectortype) (2 * sizeof(vectortype))
+#define LEN_WITH_TAIL(vectortype) (LEN_NO_TAIL(vectortype) + 3)
+
PG_MODULE_MAGIC;
-PG_FUNCTION_INFO_V1(test_lfind);
+/* workhorse for test_lfind8 */
+static void
+test_lfind8_internal(uint8 key)
+{
+ uint8 charbuf[LEN_WITH_TAIL(Vector8)];
+ const int len_no_tail = LEN_NO_TAIL(Vector8);
+ const int len_with_tail = LEN_WITH_TAIL(Vector8);
+
+ memset(charbuf, 0xFF, len_with_tail);
+ /* search tail to test one-byte-at-a-time path */
+ charbuf[len_with_tail - 1] = key;
+ if (key > 0x00 && pg_lfind8(key - 1, charbuf, len_with_tail))
+ elog(ERROR, "pg_lfind8() found nonexistent element '0x%x'", key - 1);
+ if (key < 0xFF && !pg_lfind8(key, charbuf, len_with_tail))
+ elog(ERROR, "pg_lfind8() did not find existing element '0x%x'", key);
+ if (key < 0xFE && pg_lfind8(key + 1, charbuf, len_with_tail))
+ elog(ERROR, "pg_lfind8() found nonexistent element '0x%x'", key + 1);
+
+ memset(charbuf, 0xFF, len_with_tail);
+ /* search with vector operations */
+ charbuf[len_no_tail - 1] = key;
+ if (key > 0x00 && pg_lfind8(key - 1, charbuf, len_no_tail))
+ elog(ERROR, "pg_lfind8() found nonexistent element '0x%x'", key - 1);
+ if (key < 0xFF && !pg_lfind8(key, charbuf, len_no_tail))
+ elog(ERROR, "pg_lfind8() did not find existing element '0x%x'", key);
+ if (key < 0xFE && pg_lfind8(key + 1, charbuf, len_no_tail))
+ elog(ERROR, "pg_lfind8() found nonexistent element '0x%x'", key + 1);
+}
+
+PG_FUNCTION_INFO_V1(test_lfind8);
+Datum
+test_lfind8(PG_FUNCTION_ARGS)
+{
+ test_lfind8_internal(0);
+ test_lfind8_internal(1);
+ test_lfind8_internal(0x7F);
+ test_lfind8_internal(0x80);
+ test_lfind8_internal(0x81);
+ test_lfind8_internal(0xFD);
+ test_lfind8_internal(0xFE);
+ test_lfind8_internal(0xFF);
+
+ PG_RETURN_VOID();
+}
+
+/* workhorse for test_lfind8_le */
+static void
+test_lfind8_le_internal(uint8 key)
+{
+ uint8 charbuf[LEN_WITH_TAIL(Vector8)];
+ const int len_no_tail = LEN_NO_TAIL(Vector8);
+ const int len_with_tail = LEN_WITH_TAIL(Vector8);
+
+ memset(charbuf, 0xFF, len_with_tail);
+ /* search tail to test one-byte-at-a-time path */
+ charbuf[len_with_tail - 1] = key;
+ if (key > 0x00 && pg_lfind8_le(key - 1, charbuf, len_with_tail))
+ elog(ERROR, "pg_lfind8_le() found nonexistent element <= '0x%x'", key - 1);
+ if (key < 0xFF && !pg_lfind8_le(key, charbuf, len_with_tail))
+ elog(ERROR, "pg_lfind8_le() did not find existing element <= '0x%x'", key);
+ if (key < 0xFE && !pg_lfind8_le(key + 1, charbuf, len_with_tail))
+ elog(ERROR, "pg_lfind8_le() did not find existing element <= '0x%x'", key + 1);
+
+ memset(charbuf, 0xFF, len_with_tail);
+ /* search with vector operations */
+ charbuf[len_no_tail - 1] = key;
+ if (key > 0x00 && pg_lfind8_le(key - 1, charbuf, len_no_tail))
+ elog(ERROR, "pg_lfind8_le() found nonexistent element <= '0x%x'", key - 1);
+ if (key < 0xFF && !pg_lfind8_le(key, charbuf, len_no_tail))
+ elog(ERROR, "pg_lfind8_le() did not find existing element <= '0x%x'", key);
+ if (key < 0xFE && !pg_lfind8_le(key + 1, charbuf, len_no_tail))
+ elog(ERROR, "pg_lfind8_le() did not find existing element <= '0x%x'", key + 1);
+}
+
+PG_FUNCTION_INFO_V1(test_lfind8_le);
+Datum
+test_lfind8_le(PG_FUNCTION_ARGS)
+{
+ test_lfind8_le_internal(0);
+ test_lfind8_le_internal(1);
+ test_lfind8_le_internal(0x7F);
+ test_lfind8_le_internal(0x80);
+ test_lfind8_le_internal(0x81);
+ test_lfind8_le_internal(0xFD);
+ test_lfind8_le_internal(0xFE);
+ test_lfind8_le_internal(0xFF);
+
+ PG_RETURN_VOID();
+}
+PG_FUNCTION_INFO_V1(test_lfind32);
Datum
-test_lfind(PG_FUNCTION_ARGS)
+test_lfind32(PG_FUNCTION_ARGS)
{
#define TEST_ARRAY_SIZE 135
uint32 test_array[TEST_ARRAY_SIZE] = {0};
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