Implement bignum system library using intx

Author: axic

src/eei.cpp

@@ -845,4 +845,35 @@ void WasmEngine::collectBenchmarkingData()
     }
     return ret;
   }
+
+  intx::uint256 EthereumInterface::loadBignum256(uint32_t srcOffset)
+  {
+    uint8_t data[32];
+    loadMemory(srcOffset, data, 32);
+    // FIXME: change this to little endian?
+    return intx::be::uint256(data);
+  }
+
+  void EthereumInterface::storeBignum256(intx::uint256 const& src, uint32_t dstOffset)
+  {
+    uint8_t data[32];
+    // FIXME: change this to little endian?
+    intx::be::store(data, src);
+    storeMemory(data, dstOffset, 32);
+  }
+
+  void EthereumInterface::mul256(uint32_t aOffset, uint32_t bOffset, uint32_t retOffset)
+  {
+    storeBignum256(loadBignum256(aOffset) * loadBignum256(bOffset), retOffset);
+  }
+
+  void EthereumInterface::umulmod256(uint32_t aOffset, uint32_t bOffset, uint32_t modOffset, uint32_t retOffset)
+  {
+    using intx::uint512;
+    auto a = loadBignum256(aOffset);
+    auto b = loadBignum256(bOffset);
+    auto mod = loadBignum256(modOffset);
+    auto ret = mod != 0 ? ((uint512{a} * uint512{b}) % uint512{mod}).lo : 0;
+    storeBignum256(ret, retOffset);
+  }
 }

src/eei.h

@@ -23,6 +23,8 @@
 #include <evmc/evmc.h>
 #include <evmc/evmc.hpp>
 
+#include <intx/intx.hpp>
+
 #include "exceptions.h"
 #include "helpers.h"
 
@@ -162,6 +164,10 @@ class EthereumInterface {
   uint32_t eeiCreate(uint32_t valueOffset, uint32_t dataOffset, uint32_t length, uint32_t resultOffset);
   void eeiSelfDestruct(uint32_t addressOffset);
 
+  // Bignum system library
+  void mul256(uint32_t aOffset, uint32_t bOffset, uint32_t retOffset);
+  void umulmod256(uint32_t aOffset, uint32_t bOffset, uint32_t modOffset, uint32_t retOffset);
+
 private:
   void eeiRevertOrFinish(bool revert, uint32_t offset, uint32_t size);
 
@@ -190,6 +196,9 @@ class EthereumInterface {
   evmc_uint256be loadUint128(uint32_t srcOffset);
   void storeUint128(evmc_uint256be const& src, uint32_t dstOffset);
 
+  intx::uint256 loadBignum256(uint32_t srcOffset);
+  void storeBignum256(intx::uint256 const& src, uint32_t dstOffset);
+
   inline int64_t maxCallGas(int64_t gas) { return gas - (gas / 64); }
 
   /* Checks for overflow and safely charges gas for variable length data copies */