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authorEric Fiselier <eric@efcs.ca>2018-07-26 00:34:50 +0000
committerEric Fiselier <eric@efcs.ca>2018-07-26 00:34:50 +0000
commit1e1f8ece3b3c290ed0a67e21367f0a8805ee67d4 (patch)
tree1899e2300eb27b444d2edbfc87a2361a137ca39c /libcxx/src
parent5c1e23b2e315458b8f079f543bccddff0fc09cf9 (diff)
downloadbcm5719-llvm-1e1f8ece3b3c290ed0a67e21367f0a8805ee67d4.tar.gz
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[libc++] Add hack to allow ubsan to work w/o compiler-rt (__muloti4 is undefined)
Summary: Using int128_t with UBSAN causes link errors unless compiler-rt is providing the runtime library. Specifically ubsan generates calls to __muloti4 but libgcc doesn't provide a definition. In order to avoid this, and allow users to continue using sanitized versions of libc++, this patch introduces a hack. It adds a cribbed version of the compiler-rt builtin to the libc++ filesystem sources. I don't think this approach will work in the long run, but it seems OK for now. Also see: https://bugs.llvm.org/show_bug.cgi?id=30643 https://bugs.llvm.org/show_bug.cgi?id=16404 Reviewers: mclow.lists, ldionne, rsmith, jyknight, echristo Reviewed By: echristo Subscribers: dberris, cfe-commits Differential Revision: https://reviews.llvm.org/D49828 llvm-svn: 337990
Diffstat (limited to 'libcxx/src')
-rw-r--r--libcxx/src/experimental/filesystem/int128_builtins.cpp55
1 files changed, 55 insertions, 0 deletions
diff --git a/libcxx/src/experimental/filesystem/int128_builtins.cpp b/libcxx/src/experimental/filesystem/int128_builtins.cpp
new file mode 100644
index 00000000000..b168bf525d7
--- /dev/null
+++ b/libcxx/src/experimental/filesystem/int128_builtins.cpp
@@ -0,0 +1,55 @@
+/*===-- int128_builtins.cpp - Implement __muloti4 --------------------------===
+ *
+ * The LLVM Compiler Infrastructure
+ *
+ * This file is dual licensed under the MIT and the University of Illinois Open
+ * Source Licenses. See LICENSE.TXT for details.
+ *
+ * ===----------------------------------------------------------------------===
+ *
+ * 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"
+
+#ifndef _LIBCPP_HAS_NO_INT128
+
+__attribute__((no_sanitize("undefined"))) extern "C" __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
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