Simd string2

src/parser3.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <bit>
 #include <cassert>
 #include <cctype>
 #include <cstdint>
@@ -10,6 +11,10 @@
 #include <tuple>
 #include <utility>
 
+#ifdef __x86_64__
+#include <immintrin.h>
+#endif
+
 #include "musttail.h"
 #include "tables.h"
 #include "weaseljson.h"
@@ -397,25 +402,47 @@ inline WeaselJsonStatus n_string(Parser3 *self) {
 }
 
 inline WeaselJsonStatus n_string2(Parser3 *self) {
-  auto commit = [self, before = self->buf]() {
-    int len = self->buf - before;
-    if (self->writeBuf != before) {
-      memmove(self->writeBuf, before, len);
-    }
-    self->writeBuf += len;
-  };
-begin:
-  auto meaning = tables.stringByteMeaning[uint8_t(*self->buf)];
-  if (meaning == Tables::NORMAL) {
+  const auto before = self->buf;
+
+// Advance self->buf to the first "non-normal" character
+#ifdef __x86_64__
+  for (;;) {
+    if (self->bufEnd - self->buf < 16) [[unlikely]] {
+      while (self->buf != self->bufEnd &&
+             tables.stringByteMeaning[uint8_t(*self->buf)] == Tables::NORMAL) {
         ++self->buf;
+      }
+      break;
+    }
+    __m128 x;
+    memcpy(&x, self->buf, 16);
+    const uint32_t dubquote =
+        _mm_movemask_epi8(_mm_cmpeq_epi8(_mm_set1_epi8('"'), x));
+    const uint32_t backslash =
+        _mm_movemask_epi8(_mm_cmpeq_epi8(_mm_set1_epi8('\\'), x));
+    const uint32_t control_or_negative =
+        _mm_movemask_epi8(_mm_cmpgt_epi8(_mm_set1_epi8(0x20), x));
+    const uint32_t non_normal = dubquote | backslash | control_or_negative;
+    if (non_normal) {
+      self->buf += std::countr_zero(non_normal);
+      break;
+    }
+    self->buf += 16;
+  }
+#else
+#error "port me"
+#endif
+
+  int len = self->buf - before;
+  memmove(self->writeBuf, before, len);
+  self->writeBuf += len;
+
   if (self->buf == self->bufEnd) {
-      commit();
-      MUSTTAIL return Parser3::keepGoing(self);
+    self->flushString();
+    return WeaselJson_AGAIN;
   }
-    goto begin;
-  }
-  commit();
-  switch (meaning) {
+
+  switch (tables.stringByteMeaning[uint8_t(*self->buf)]) {
   case Tables::NORMAL:
     __builtin_unreachable();
   case Tables::DUBQUOTE: