diff options
Diffstat (limited to 'libevmasm/ConstantOptimiser.cpp')
| -rw-r--r-- | libevmasm/ConstantOptimiser.cpp | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/libevmasm/ConstantOptimiser.cpp b/libevmasm/ConstantOptimiser.cpp index a1dfd21c..c1d61b88 100644 --- a/libevmasm/ConstantOptimiser.cpp +++ b/libevmasm/ConstantOptimiser.cpp @@ -232,6 +232,54 @@ AssemblyItems ComputeMethod::findRepresentation(u256 const& _value) } } +bool ComputeMethod::checkRepresentation(u256 const& _value) +{ + // This is a tiny EVM that can only evaluate some instructions. + vector<u256> stack; + for (AssemblyItem const& item: m_routine) + { + switch (item.type()) + { + case Operation: + { + if (stack.size() < size_t(item.arguments())) + return false; + u256* sp = &stack.back(); + switch (item.instruction()) + { + case Instruction::MUL: + sp[-1] = sp[0] * sp[-1]; + break; + case Instruction::EXP: + if (sp[-1] > 0xff) + return false; + sp[-1] = boost::multiprecision::pow(sp[0], unsigned(sp[-1])); + break; + case Instruction::ADD: + sp[-1] = sp[0] + sp[-1]; + break; + case Instruction::SUB: + sp[-1] = sp[0] - sp[-1]; + break; + case Instruction::NOT: + sp[0] = ~sp[0]; + break; + default: + return false; + } + stack.resize(stack.size() + item.deposit()); + break; + } + case Push: + stack.push_back(item.data()); + break; + default: + return false; + } + } + return stack.size() == 1 && stack.front() == _value; +} + bigint ComputeMethod::gasNeeded(AssemblyItems const& _routine) { size_t numExps = count(_routine.begin(), _routine.end(), Instruction::EXP); |