Merge #9572: Skip witness sighash cache for non-segwit transactions

0da49b5 Skip precompute sighash for transactions without witness (Johnson Lau)

Pull request description:

  This saves unnecessary hash caching for non-segwit transactions, but I am not sure if the difference is noticeable.

Tree-SHA512: 5cd733a729a52a45781510b3572b26e76837a94155caa14311c6d23a27a12e9613ff278dfc2592e21f640202782f22c5ad00fca85c4de5efacaa617c48ccb08d

src/script/interpreter.cpp

@@ -1168,9 +1168,13 @@ uint256 GetOutputsHash(const CTransaction& txTo) {
 
 PrecomputedTransactionData::PrecomputedTransactionData(const CTransaction& txTo)
 {
+    // Cache is calculated only for transactions with witness
+    if (txTo.HasWitness()) {
         hashPrevouts = GetPrevoutHash(txTo);
         hashSequence = GetSequenceHash(txTo);
         hashOutputs = GetOutputsHash(txTo);
+        ready = true;
+    }
 }
 
 uint256 SignatureHash(const CScript& scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType, const CAmount& amount, SigVersion sigversion, const PrecomputedTransactionData* cache)
@@ -1181,18 +1185,19 @@ uint256 SignatureHash(const CScript& scriptCode, const CTransaction& txTo, unsig
         uint256 hashPrevouts;
         uint256 hashSequence;
         uint256 hashOutputs;
+        const bool cacheready = cache && cache->ready;
 
         if (!(nHashType & SIGHASH_ANYONECANPAY)) {
-            hashPrevouts = cache ? cache->hashPrevouts : GetPrevoutHash(txTo);
+            hashPrevouts = cacheready ? cache->hashPrevouts : GetPrevoutHash(txTo);
         }
 
         if (!(nHashType & SIGHASH_ANYONECANPAY) && (nHashType & 0x1f) != SIGHASH_SINGLE && (nHashType & 0x1f) != SIGHASH_NONE) {
-            hashSequence = cache ? cache->hashSequence : GetSequenceHash(txTo);
+            hashSequence = cacheready ? cache->hashSequence : GetSequenceHash(txTo);
         }
 
 
         if ((nHashType & 0x1f) != SIGHASH_SINGLE && (nHashType & 0x1f) != SIGHASH_NONE) {
-            hashOutputs = cache ? cache->hashOutputs : GetOutputsHash(txTo);
+            hashOutputs = cacheready ? cache->hashOutputs : GetOutputsHash(txTo);
         } else if ((nHashType & 0x1f) == SIGHASH_SINGLE && nIn < txTo.vout.size()) {
             CHashWriter ss(SER_GETHASH, 0);
             ss << txTo.vout[nIn];

src/script/interpreter.h

@@ -113,6 +113,7 @@ bool CheckSignatureEncoding(const std::vector<unsigned char> &vchSig, unsigned i
 struct PrecomputedTransactionData
 {
     uint256 hashPrevouts, hashSequence, hashOutputs;
+    bool ready = false;
 
     explicit PrecomputedTransactionData(const CTransaction& tx);
 };