1 files changed, 54 insertions, 0 deletions
diff --git a/gnu/llvm/libcxx/src/filesystem/int128_builtins.cpp b/gnu/llvm/libcxx/src/filesystem/int128_builtins.cpp
new file mode 100644
index 00000000000..ed531ee145a
--- /dev/null
+++ b/gnu/llvm/libcxx/src/filesystem/int128_builtins.cpp
@@ -0,0 +1,54 @@
+/*===-- int128_builtins.cpp - Implement __muloti4 --------------------------===
+ *
+ * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+ * See https://llvm.org/LICENSE.txt for license information.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ *
+ * ===----------------------------------------------------------------------===
+ *
+ * This file implements __muloti4, and is stolen from the compiler_rt library.
+ *
+ * FIXME: we steal and re-compile it into filesystem, which uses __int128_t,
+ * and requires this builtin when sanitized. See llvm.org/PR30643
+ *
+ * ===----------------------------------------------------------------------===
+ */
+#include "__config"
+#include "climits"
+
+#if !defined(_LIBCPP_HAS_NO_INT128)
+
+extern "C" __attribute__((no_sanitize("undefined"))) _LIBCPP_FUNC_VIS
+__int128_t __muloti4(__int128_t a, __int128_t b, int* overflow) {
+  const int N = (int)(sizeof(__int128_t) * CHAR_BIT);
+  const __int128_t MIN = (__int128_t)1 << (N - 1);
+  const __int128_t MAX = ~MIN;
+  *overflow = 0;
+  __int128_t result = a * b;
+  if (a == MIN) {
+    if (b != 0 && b != 1)
+      *overflow = 1;
+    return result;
+  }
+  if (b == MIN) {
+    if (a != 0 && a != 1)
+      *overflow = 1;
+    return result;
+  }
+  __int128_t sa = a >> (N - 1);
+  __int128_t abs_a = (a ^ sa) - sa;
+  __int128_t sb = b >> (N - 1);
+  __int128_t abs_b = (b ^ sb) - sb;
+  if (abs_a < 2 || abs_b < 2)
+    return result;
+  if (sa == sb) {
+    if (abs_a > MAX / abs_b)
+      *overflow = 1;
+  } else {
+    if (abs_a > MIN / -abs_b)
+      *overflow = 1;
+  }
+  return result;
+}
+
+#endif