Arm64 specific support for lj_new_str random hash optimization

src/Makefile

@@ -50,7 +50,7 @@ CCOPT= -O2 -fomit-frame-pointer
 CCOPT_x86= -march=i686 -msse -msse2 -mfpmath=sse
 CCOPT_x64=
 CCOPT_arm=
-CCOPT_arm64=
+CCOPT_arm64= -march=armv8-a+crc
 CCOPT_ppc=
 CCOPT_mips=
 #

src/arm64/src/lj_str_hash_arm64.h

@@ -0,0 +1,271 @@
+/*
+ * This file defines string hash function using CRC32. It takes advantage of
+ * Arm64 hardware support (crc32 instruction) to speedup the CRC32
+ * computation. The hash functions try to compute CRC32 of length and up
+ * to 128 bytes of given string.
+ */
+
+#ifndef _LJ_STR_HASH_ARM64_H_
+#define _LJ_STR_HASH_ARM64_H_
+
+#if defined(__aarch64__) && defined(__GNUC__)
+
+#include <stdint.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <time.h>
+#include <sys/auxv.h>
+#include <stdio.h>
+#include <arm_acle.h>
+
+#include "../../lj_def.h"
+
+#ifndef HWCAP_CRC32
+#define HWCAP_CRC32             (1 << 7)
+#endif /* HWCAP for crc32 */
+
+#ifndef LJ_AINLINE
+#define LJ_AINLINE   inline __attribute__((always_inline))
+#endif
+
+#ifdef __MINGW32__
+#define random()  ((long) rand())
+#define srandom(seed)  srand(seed)
+#endif
+
+extern uint32_t lj_str_original_hash(const char *str, size_t lenx);
+static LJ_AINLINE uint32_t lj_str_hash(const char* str, size_t len);
+/* lj_str hash function determined at runtime */
+typedef uint32_t (*lj_str_hash_func)(const char *str, size_t lenx);
+lj_str_hash_func LJ_STR_HASH;
+
+static const uint64_t* cast_uint64p(const char* str)
+{
+  return (const uint64_t*)(void*)str;
+}
+
+static const uint32_t* cast_uint32p(const char* str)
+{
+  return (const uint32_t*)(void*)str;
+}
+
+static LJ_AINLINE uint32_t lj_str_hash_1_4(const char* str, uint32_t len)
+{
+  uint32_t v = str[0], h = 0;
+  v = (v << 8) | str[len >> 1];
+  v = (v << 8) | str[len - 1];
+  v = (v << 8) | len;
+  return __crc32cw(h, v);
+}
+
+static LJ_AINLINE uint32_t lj_str_hash_4_16(const char* str, size_t len)
+{
+  uint64_t v1, v2, h = 0;
+
+  if (len >= 8) {
+	v1 = *cast_uint64p(str);
+	v2 = *cast_uint64p(str + len - 8);
+  } else {
+	v1 = *cast_uint32p(str);
+	v2 = *cast_uint32p(str + len - 4);
+  }
+
+  h = __crc32cw(h, len);
+  h = __crc32cd(h, v1);
+  h = __crc32cd(h, v2);
+
+  return h;
+}
+
+static LJ_AINLINE uint32_t lj_str_hash_16_128(const char* str, size_t len)
+{
+  uint64_t h1 = 0, h2 = 0;
+  uint32_t i;
+
+  h1 = __crc32cw(h1, len);
+
+  for (i = 0; i < len - 16; i += 16) {
+	h1 += __crc32cd(h1, *cast_uint64p(str + i));
+	h2 += __crc32cd(h2, *cast_uint64p(str + i + 8));
+  }
+
+  h1 = __crc32cd(h1, *cast_uint64p(str + len - 16));
+  h2 = __crc32cd(h2, *cast_uint64p(str + len - 8));
+
+  return __crc32cw(h1, h2);
+}
+
+/* **************************************************************************
+ *
+ *  Following is code about hashing string with length >= 128
+ *
+ * **************************************************************************
+ */
+
+static uint32_t random_pos[32][2];
+static const int8_t log2_tab[128] = { -1,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,4,4,
+  4,4,4,4,4,4,4,4,4,4,4,4,4,4,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
+  5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,6,6,6,6,6,6,6,6,6,6,6,6,
+  6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
+  6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6 };
+
+/* return floor(log2(n)) */
+static LJ_AINLINE uint32_t log2_floor(uint32_t n)
+{
+  if (n <= 127) {
+    return log2_tab[n];
+  }
+
+  if ((n >> 8) <= 127) {
+    return log2_tab[n >> 8] + 8;
+  }
+
+  if ((n >> 16) <= 127) {
+    return log2_tab[n >> 16] + 16;
+  }
+
+  if ((n >> 24) <= 127) {
+    return log2_tab[n >> 24] + 24;
+  }
+
+  return 31;
+}
+
+#define POW2_MASK(n) ((1L << (n)) - 1)
+/* This function is to populate `random_pos` such that random_pos[i][*]
+ * contains random value in the range of [2**i, 2**(i+1)).
+ */
+static void arm64_init_random(void)
+{
+  int i, seed, rml;
+
+  /* Calculate the ceil(log2(RAND_MAX)) */
+  rml = log2_floor(RAND_MAX);
+  if (RAND_MAX & (RAND_MAX - 1)) {
+    rml += 1;
+  }
+
+  /* Init seed */
+  seed = 0;
+  seed = __crc32cw(seed, getpid());
+  seed = __crc32cw(seed, time(NULL));
+  srandom(seed);
+
+  /* Now start to populate the random_pos[][]. */
+  for (i = 0; i < 3; i++) {
+    /* No need to provide random value for chunk smaller than 8 bytes */
+    random_pos[i][0] = random_pos[i][1] = 0;
+  }
+
+  for (; i < rml; i++) {
+    random_pos[i][0] = random() & POW2_MASK(i+1);
+    random_pos[i][1] = random() & POW2_MASK(i+1);
+  }
+
+  for (; i < 31; i++) {
+    int j;
+    for (j = 0; j < 2; j++) {
+      uint32_t v, scale;
+      scale = random_pos[i - rml][0];
+      if (scale == 0) {
+         scale = 1;
+      }
+      v = (random() * scale) & POW2_MASK(i+1);
+      random_pos[i][j] = v;
+    }
+  }
+}
+#undef POW2_MASK
+
+void __attribute__((constructor)) arm64_init_constructor()
+{
+    // Check if crc32 supported.
+    unsigned long hwcap;
+    hwcap = getauxval(AT_HWCAP);
+    if (hwcap & HWCAP_CRC32) {
+	LJ_STR_HASH = lj_str_hash;
+    }
+    else {
+	LJ_STR_HASH = lj_str_original_hash;
+    }
+
+    // init random
+    arm64_init_random();
+}
+
+/* Return a pre-computed random number in the range of [1**chunk_sz_order,
+ * 1**(chunk_sz_order+1)). It is "unsafe" in the sense that the return value
+ * may be greater than chunk-size; it is up to the caller to make sure
+ * "chunk-base + return-value-of-this-func" has valid virtual address.
+ */
+static LJ_AINLINE uint32_t get_random_pos_unsafe(uint32_t chunk_sz_order,
+       uint32_t idx)
+{
+  uint32_t pos = random_pos[chunk_sz_order][idx & 1];
+  return pos;
+}
+
+static LJ_NOINLINE uint32_t lj_str_hash_128_above(const char* str,
+  uint32_t len)
+{
+  uint32_t chunk_num, chunk_sz, chunk_sz_log2, i, pos1, pos2;
+  uint32_t h1, h2, v;
+  const char* chunk_ptr;
+
+  chunk_num = 16;
+  chunk_sz = len / chunk_num;
+  chunk_sz_log2 = log2_floor(chunk_sz);
+
+  pos1 = get_random_pos_unsafe(chunk_sz_log2, 0);
+  pos2 = get_random_pos_unsafe(chunk_sz_log2, 1);
+
+  h1 = 0;
+  h1 = __crc32cw(h1, len);
+  h2 = 0;
+
+  /* loop over 14 chunks, 2 chunks at a time */
+  for (i = 0, chunk_ptr = str; i < (chunk_num / 2 - 1);
+       chunk_ptr += chunk_sz, i++) {
+
+    v = *cast_uint64p(chunk_ptr + pos1);
+    h1 = __crc32cd(h1, v);
+
+    v = *cast_uint64p(chunk_ptr + chunk_sz + pos2);
+    h2 = __crc32cd(h2, v);
+  }
+
+  /* the last two chunks */
+  v = *cast_uint64p(chunk_ptr + pos1);
+  h1 = __crc32cd(h1, v);
+
+  v = *cast_uint64p(chunk_ptr + chunk_sz - 8 - pos2);
+  h2 = __crc32cd(h2, v);
+
+  /* process the trailing part */
+  h1 = __crc32cd(h1, *cast_uint64p(str));
+  h2 = __crc32cd(h2, *cast_uint64p(str + len - 8));
+
+  h1 = __crc32cw(h1, h2);
+  return h1;
+}
+
+
+/* NOTE: the "len" should not be zero */
+static LJ_AINLINE uint32_t lj_str_hash(const char* str, size_t len)
+{
+  if (len < 128) {
+    if (len >= 16) { 
+      return lj_str_hash_16_128(str, len);
+    }
+
+    if ((len >= 4) && (len < 16)) { 
+      return lj_str_hash_4_16(str, len);
+    }
+
+    return lj_str_hash_1_4(str, len);
+  }
+  return lj_str_hash_128_above(str, len);
+}
+
+#endif // defined(__aarch64__)
+#endif // _LJ_STR_HASH_ARM64_H_

src/lj_str.c

@@ -163,13 +163,18 @@ lj_str_indep_hash(GCstr *str) {
   return lj_str_original_hash(strdata(str), str->len);
 }
 
+#if defined(__aarch64__)
+/* AArch64 CRC32 support determined at runtime */
+#include "arm64/src/lj_str_hash_arm64.h"
+#else /* x64 */
 #include "x64/src/lj_str_hash_x64.h"
 
 #if defined(LJ_ARCH_STR_HASH)
 #define LJ_STR_HASH LJ_ARCH_STR_HASH
 #else
 #define LJ_STR_HASH lj_str_original_hash
 #endif
+#endif
 
 /* Intern a string and return string object. */
 GCstr *lj_str_new(lua_State *L, const char *str, size_t lenx)