wallet: Use wallet's TXO set in AvailableCoins

Instead of iterating every transaction and every output stored in wallet
when trying to figure out what outputs can be spent, iterate the TXO set
which should be a lot smaller.

src/wallet/spend.cpp

@@ -330,15 +330,25 @@ CoinsResult AvailableCoins(const CWallet& wallet,
     std::vector<COutPoint> outpoints;
 
     std::set<Txid> trusted_parents;
-    for (const auto& entry : wallet.mapWallet)
+    // Cache for whether each tx passes the tx level checks (first bool), and whether the transaction is "safe" (second bool)
-    {
+    std::unordered_map<uint256, std::pair<bool, bool>, SaltedTxidHasher> tx_safe_cache;
-        const Txid& txid = entry.first;
+    for (const auto& [outpoint, txo] : wallet.GetTXOs()) {
-        const CWalletTx& wtx = entry.second;
+        const CWalletTx& wtx = txo.GetWalletTx();
+        const CTxOut& output = txo.GetTxOut();
+
+        if (tx_safe_cache.contains(outpoint.hash) && !tx_safe_cache.at(outpoint.hash).first) {
+            continue;
+        }
+
+        int nDepth = wallet.GetTxDepthInMainChain(wtx);
+
+        // Perform tx level checks if we haven't already come across outputs from this tx before.
+        if (!tx_safe_cache.contains(outpoint.hash)) {
+            tx_safe_cache[outpoint.hash] = {false, false};
 
             if (wallet.IsTxImmatureCoinBase(wtx) && !params.include_immature_coinbase)
                 continue;
 
-        int nDepth = wallet.GetTxDepthInMainChain(wtx);
             if (nDepth < 0)
                 continue;
 
@@ -388,11 +398,12 @@ CoinsResult AvailableCoins(const CWallet& wallet,
                 continue;
             }
 
-        bool tx_from_me = CachedTxIsFromMe(wallet, wtx, ISMINE_ALL);
+            tx_safe_cache[outpoint.hash] = {true, safeTx};
-
+        }
-        for (unsigned int i = 0; i < wtx.tx->vout.size(); i++) {
+        const auto& [tx_ok, tx_safe] = tx_safe_cache.at(outpoint.hash);
-            const CTxOut& output = wtx.tx->vout[i];
+        if (!Assume(tx_ok)) {
-            const COutPoint outpoint(txid, i);
+            continue;
+        }
 
         if (output.nValue < params.min_amount || output.nValue > params.max_amount)
             continue;
@@ -408,15 +419,14 @@ CoinsResult AvailableCoins(const CWallet& wallet,
             continue;
 
         isminetype mine = wallet.IsMine(output);
-
+        assert(mine != ISMINE_NO);
-            if (mine == ISMINE_NO) {
-                continue;
-            }
 
         if (!allow_used_addresses && wallet.IsSpentKey(output.scriptPubKey)) {
             continue;
         }
 
+        bool tx_from_me = CachedTxIsFromMe(wallet, wtx, ISMINE_ALL);
+
         std::unique_ptr<SigningProvider> provider = wallet.GetSolvingProvider(output.scriptPubKey);
 
         int input_bytes = CalculateMaximumSignedInputSize(output, COutPoint(), provider.get(), can_grind_r, coinControl);
@@ -445,7 +455,7 @@ CoinsResult AvailableCoins(const CWallet& wallet,
         }
 
         result.Add(GetOutputType(type, is_from_p2sh),
-                       COutput(outpoint, output, nDepth, input_bytes, spendable, solvable, safeTx, wtx.GetTxTime(), tx_from_me, feerate));
+                   COutput(outpoint, output, nDepth, input_bytes, spendable, solvable, tx_safe, wtx.GetTxTime(), tx_from_me, feerate));
 
         outpoints.push_back(outpoint);
 
@@ -461,7 +471,6 @@ CoinsResult AvailableCoins(const CWallet& wallet,
             return result;
         }
     }
-    }
 
     if (feerate.has_value()) {
         std::map<COutPoint, CAmount> map_of_bump_fees = wallet.chain().calculateIndividualBumpFees(outpoints, feerate.value());