Start work on vectorizing searches

kitty/simd-string.c

@@ -0,0 +1,66 @@
+/*
+ * simd-string.c
+ * Copyright (C) 2023 Kovid Goyal <kovid at kovidgoyal.net>
+ *
+ * Distributed under terms of the GPL3 license.
+ */
+
+#include "data-types.h"
+#include "simd-string.h"
+#include <immintrin.h>
+
+uint8_t
+byte_loader_peek(const ByteLoader *self) {
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+    return self->m & 0xff;
+#define SHIFT_OP >>
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+    // no idea if this is correct needs testing
+    return (self->m >> ((sizeof(self->m) - 1)*8)) & 0xff;
+#define SHIFT_OP <<
+#else
+#error "Unsupported endianness"
+#endif
+}
+
+void
+byte_loader_init(ByteLoader *self, const uint8_t *buf, unsigned int sz) {
+    size_t extra = ((uintptr_t)buf) % sizeof(BYTE_LOADER_T);
+    if (extra) { // align loading
+        buf -= extra; sz += extra;
+    }
+    size_t s = MIN(sz, sizeof(self->m));
+    self->next_load_at = buf + s;
+    self->num_left = sz - extra;
+    self->digits_left = sizeof(self->m) - extra;
+    self->m = (*((BYTE_LOADER_T*)buf)) SHIFT_OP (8 * extra);
+    self->sz_of_next_load = sz - s;
+}
+
+uint8_t
+byte_loader_next(ByteLoader *self) {
+    uint8_t ans = byte_loader_peek(self);
+    self->num_left--; self->digits_left--; self->m = self->m SHIFT_OP 8;
+    if (!self->digits_left) byte_loader_init(self, self->next_load_at, self->sz_of_next_load);
+    return ans;
+}
+#undef SHIFT_OP
+
+
+static uint8_t*
+find_either_of_two_chars_simple(uint8_t *haystack, const size_t sz, const uint8_t x, const uint8_t y) {
+    ByteLoader b; byte_loader_init(&b, haystack, sz);
+    uint8_t ch;
+    while (b.num_left) {
+        ch = byte_loader_next(&b);
+        if (ch == x || ch == y) {
+            return haystack + sz - b.num_left - 1;
+        }
+    }
+    return NULL;
+}
+
+uint8_t*
+find_either_of_two_chars(uint8_t *haystack, const size_t sz, const uint8_t a, const uint8_t b) {
+    return find_either_of_two_chars_simple(haystack, sz, a, b);
+}