libcxx: fix bogus integer sanitizer warnings in hash helpers

Author: jcelerier

libcxx/include/__config

@@ -1156,8 +1156,10 @@ typedef __char32_t char32_t;
 // Allow for build-time disabling of unsigned integer sanitization
 #  if __has_attribute(no_sanitize) && !defined(_LIBCPP_COMPILER_GCC)
 #    define _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK __attribute__((__no_sanitize__("unsigned-integer-overflow")))
+#    define _LIBCPP_DISABLE_UBSAN_INTEGER_CHECK(reason) __attribute__((__no_sanitize__("integer")))
 #  else
 #    define _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
+#    define _LIBCPP_DISABLE_UBSAN_INTEGER_CHECK(reason)
 #  endif
 
 #  if __has_feature(nullability)

libcxx/include/__functional/hash.h

@@ -132,11 +132,13 @@ struct __murmur2_or_cityhash<_Size, 64> {
   static const _Size __k2 = 0x9ae16a3b2f90404fULL;
   static const _Size __k3 = 0xc949d7c7509e6557ULL;
 
-  _LIBCPP_HIDE_FROM_ABI static _Size __rotate(_Size __val, int __shift) {
+  _LIBCPP_HIDE_FROM_ABI static _Size _LIBCPP_DISABLE_UBSAN_INTEGER_CHECK("shifting can cause unsigned overflow")
+      __rotate(_Size __val, int __shift) {
     return __shift == 0 ? __val : ((__val >> __shift) | (__val << (64 - __shift)));
   }
 
-  _LIBCPP_HIDE_FROM_ABI static _Size __rotate_by_at_least_1(_Size __val, int __shift) {
+  _LIBCPP_HIDE_FROM_ABI static _Size _LIBCPP_DISABLE_UBSAN_INTEGER_CHECK("shifting can cause unsigned overflow")
+      __rotate_by_at_least_1(_Size __val, int __shift) {
     return (__val >> __shift) | (__val << (64 - __shift));
   }