Disable msan in clmul code

Author: sipa

src/fields/clmul_common_impl.h

@@ -15,7 +15,18 @@
 
 namespace {
 
-template<typename I, int BITS, I MOD> I MulWithClMulReduce(I a, I b)
+// The memory sanitizer in clang 9 cannot reason through _mm_clmulepi64_si128 calls.
+// Disable memory sanitization entirely in them for now.
+#if defined(__has_feature)
+#  if __has_feature(memory_sanitizer)
+#    define NO_SANITIZE_MEMORY __attribute__((no_sanitize("memory")))
+#  endif
+#endif
+#ifndef NO_SANITIZE_MEMORY
+#  define NO_SANITIZE_MEMORY
+#endif
+
+template<typename I, int BITS, I MOD> NO_SANITIZE_MEMORY I MulWithClMulReduce(I a, I b)
 {
     static constexpr I MASK = Mask<BITS, I>();
 
@@ -52,7 +63,7 @@ template<typename I, int BITS, I MOD> I MulWithClMulReduce(I a, I b)
     }
 }
 
-template<typename I, int BITS, int POS> I MulTrinomial(I a, I b)
+template<typename I, int BITS, int POS> NO_SANITIZE_MEMORY I MulTrinomial(I a, I b)
 {
     static constexpr I MASK = Mask<BITS, I>();