1 files changed, 12 insertions, 10 deletions
diff --git a/src/support/hash.h b/src/support/hash.h
index b99902616..ba1001d66 100644
--- a/src/support/hash.h
+++ b/src/support/hash.h
@@ -28,29 +28,31 @@ template<typename T> inline std::size_t hash(const T& value) {
 }
 
 // Combines two digests into the first digest. Use instead of `rehash` if
-// `otherDigest` is another digest and not a `size_t` value. This is also useful
-// when you want deterministic behavior across systems, as this method does not
-// call std::hash, so it does not depend on the behavior of the local machine's
-// C++ standard library implementation.
+// `otherDigest` is another digest. This is also deterministic, aside from
+// possible differences in size_t (see deterministic_hash_combine, below).
 inline void hash_combine(std::size_t& digest, const std::size_t otherDigest) {
   // see: boost/container_hash/hash.hpp
   // The constant is the N-bits reciprocal of the golden ratio:
   //  phi = (1 + sqrt(5)) / 2
-#if SIZE_MAX == UINT64_MAX
   //  trunc(2^64 / phi) = 0x9e3779b97f4a7c15
   digest ^= otherDigest + 0x9e3779b97f4a7c15 + (digest << 12) + (digest >> 4);
-#else
-  //  trunc(2^32 / phi) = 0x9e3779b9
-  digest ^= otherDigest + 0x9e3779b9 + (digest << 6) + (digest >> 2);
-#endif
 }
 
 // Hashes `value` and combines the resulting digest into the existing digest.
-// Use instead of `hash_combine` if `value` is not another digest.
+// Use instead of `hash_combine` if `value` is not another digest (i.e., it
+// needs to be hashed first).
 template<typename T> inline void rehash(std::size_t& digest, const T& value) {
   hash_combine(digest, hash(value));
 }
 
+// Similar to hash_combine, but guaranteed to produce the exact same results on
+// all machines, even ones where size_t differs. This is essentially identical
+// to hash_combine, but the types are all uint64_t.
+inline void deterministic_hash_combine(uint64_t& digest,
+                                       const uint64_t otherDigest) {
+  digest ^= otherDigest + 0x9e3779b97f4a7c15 + (digest << 12) + (digest >> 4);
+}
+
 } // namespace wasm
 
 namespace std {