kernel: De-globalize script execution cache hasher

Move it to the ChainstateManager class.

Author: TheCharlatan

src/validation.cpp

@@ -2094,17 +2094,15 @@ bool CScriptCheck::operator()() {
     return VerifyScript(scriptSig, m_tx_out.scriptPubKey, witness, nFlags, CachingTransactionSignatureChecker(ptxTo, nIn, m_tx_out.nValue, cacheStore, *txdata), &error);
 }
 
-static CSHA256 g_scriptExecutionCacheHasher;
-
 ValidationCache::ValidationCache(const size_t script_execution_cache_bytes)
 {
     // Setup the salted hasher
     uint256 nonce = GetRandHash();
     // We want the nonce to be 64 bytes long to force the hasher to process
     // this chunk, which makes later hash computations more efficient. We
     // just write our 32-byte entropy twice to fill the 64 bytes.
-    g_scriptExecutionCacheHasher.Write(nonce.begin(), 32);
-    g_scriptExecutionCacheHasher.Write(nonce.begin(), 32);
+    m_script_execution_cache_hasher.Write(nonce.begin(), 32);
+    m_script_execution_cache_hasher.Write(nonce.begin(), 32);
 
     const auto [num_elems, approx_size_bytes] = m_script_execution_cache.setup_bytes(script_execution_cache_bytes);
     LogPrintf("Using %zu MiB out of %zu MiB requested for script execution cache, able to store %zu elements\n",
@@ -2148,7 +2146,7 @@ bool CheckInputScripts(const CTransaction& tx, TxValidationState& state,
     // properly commits to the scriptPubKey in the inputs view of that
     // transaction).
     uint256 hashCacheEntry;
-    CSHA256 hasher = g_scriptExecutionCacheHasher;
+    CSHA256 hasher = validation_cache.ScriptExecutionCacheHasher();
     hasher.Write(UCharCast(tx.GetWitnessHash().begin()), 32).Write((unsigned char*)&flags, sizeof(flags)).Finalize(hashCacheEntry.begin());
     AssertLockHeld(cs_main); //TODO: Remove this requirement by making CuckooCache not require external locks
     if (validation_cache.m_script_execution_cache.contains(hashCacheEntry, !cacheFullScriptStore)) {

src/validation.h

@@ -366,13 +366,20 @@ static_assert(std::is_nothrow_destructible_v<CScriptCheck>);
  */
 class ValidationCache
 {
+private:
+    //! Pre-initialized hasher to avoid having to recreate it for every hash calculation.
+    CSHA256 m_script_execution_cache_hasher;
+
 public:
     CuckooCache::cache<uint256, SignatureCacheHasher> m_script_execution_cache;
 
     ValidationCache(size_t script_execution_cache_bytes);
 
     ValidationCache(const ValidationCache&) = delete;
     ValidationCache& operator=(const ValidationCache&) = delete;
+
+    //! Return a copy of the pre-initialized hasher.
+    CSHA256 ScriptExecutionCacheHasher() const { return m_script_execution_cache_hasher; }
 };
 
 /** Functions for validating blocks and updating the block tree */