Make some quick fixes and cleanup

libc/intrin/stpcpy.c

@@ -0,0 +1,61 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/str/str.h"
+
+typedef char xmm_u __attribute__((__vector_size__(16), __aligned__(1)));
+typedef char xmm_t __attribute__((__vector_size__(16), __aligned__(16)));
+
+static inline noasan size_t stpcpy_sse2(char *d, const char *s, size_t i) {
+  xmm_t v, z = {0};
+  for (;;) {
+    v = *(xmm_t *)(s + i);
+    if (!__builtin_ia32_pmovmskb128(v == z)) {
+      *(xmm_u *)(d + i) = v;
+      i += 16;
+    } else {
+      break;
+    }
+  }
+  return i;
+}
+
+/**
+ * Copies bytes from 𝑠 to 𝑑 until a NUL is encountered.
+ *
+ * @param 𝑑 is destination memory
+ * @param 𝑠 is a NUL-terminated string
+ * @note 𝑑 and 𝑠 can't overlap
+ * @return pointer to nul byte
+ * @asyncsignalsafe
+ */
+char *stpcpy(char *d, const char *s) {
+  size_t i;
+  for (i = 0; (uintptr_t)(s + i) & 15; ++i) {
+    if (!(d[i] = s[i])) {
+      return d + i;
+    }
+  }
+  i = stpcpy_sse2(d, s, i);
+  for (;;) {
+    if (!(d[i] = s[i])) {
+      return d + i;
+    }
+    ++i;
+  }
+}