Fixed implementation of EXP opcode (wrong results when exponent >= 2^32)

libevm/VM.h

@@ -241,9 +241,9 @@ template <class Ext> eth::bytesConstRef eth::VM::go(Ext& _ext, OnOpFunc const& _
 		{
 			require(2);
 			auto base = m_stack.back();
-			unsigned expon = (unsigned)m_stack[m_stack.size() - 2];
+			auto expon = m_stack[m_stack.size() - 2];
 			m_stack.pop_back();
-			m_stack.back() = boost::multiprecision::pow(base, expon);
+			m_stack.back() = (u256)boost::multiprecision::powm((bigint)base, (bigint)expon, bigint(2) << 256);
 			break;
 		}
 		case Instruction::NEG:

liblll/Assembly.cpp

@@ -230,7 +230,7 @@ Assembly& Assembly::optimise(bool _enable)
         { Instruction::SDIV, [](u256 a, u256 b)->u256{return s2u(u2s(a) / u2s(b));} },
 		{ Instruction::MOD, [](u256 a, u256 b)->u256{return a % b;} },
         { Instruction::SMOD, [](u256 a, u256 b)->u256{return s2u(u2s(a) % u2s(b));} },
-		{ Instruction::EXP, [](u256 a, u256 b)->u256{return boost::multiprecision::pow(a, (unsigned)b);} },
+		{ Instruction::EXP, [](u256 a, u256 b)->u256{return (u256)boost::multiprecision::powm((bigint)a, (bigint)b, bigint(2) << 256);} },
 		{ Instruction::LT, [](u256 a, u256 b)->u256{return a < b ? 1 : 0;} },
 		{ Instruction::GT, [](u256 a, u256 b)->u256{return a > b ? 1 : 0;} },
         { Instruction::SLT, [](u256 a, u256 b)->u256{return u2s(a) < u2s(b) ? 1 : 0;} },