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#include "GasMeter.h"
#include <llvm/IR/GlobalVariable.h>
#include <llvm/IR/Function.h>
#include <libevmface/Instruction.h>
#include <libevm/FeeStructure.h>
#include "Type.h"
namespace evmcc
{
using namespace dev::eth; // We should move all the JIT code into dev::eth namespace
namespace // Helper functions
{
uint64_t getStepCost(dev::eth::Instruction inst) // TODO: Add this function to FeeSructure
{
switch (inst)
{
case Instruction::STOP:
case Instruction::SUICIDE:
return 0;
case Instruction::SSTORE:
return static_cast<uint64_t>(c_sstoreGas);
case Instruction::SLOAD:
return static_cast<uint64_t>(c_sloadGas);
case Instruction::SHA3:
return static_cast<uint64_t>(c_sha3Gas);
case Instruction::BALANCE:
return static_cast<uint64_t>(c_sha3Gas);
case Instruction::CALL:
case Instruction::CALLCODE:
return static_cast<uint64_t>(c_callGas);
case Instruction::CREATE:
return static_cast<uint64_t>(c_createGas);
default: // Assumes instruction code is valid
return static_cast<uint64_t>(c_stepGas);
}
}
bool isCostBlockEnd(Instruction _inst)
{
// Basic block terminators like STOP are not needed on the list
// as cost will be commited at the end of basic block
switch (_inst)
{
case Instruction::CALLDATACOPY:
case Instruction::CODECOPY:
case Instruction::MLOAD:
case Instruction::MSTORE:
case Instruction::MSTORE8:
case Instruction::SSTORE:
case Instruction::GAS:
case Instruction::CREATE:
case Instruction::CALL:
case Instruction::CALLCODE:
return true;
default:
return false;
}
}
}
GasMeter::GasMeter(llvm::IRBuilder<>& _builder, llvm::Module* _module):
m_builder(_builder)
{
m_gas = new llvm::GlobalVariable(*_module, Type::i256, false, llvm::GlobalVariable::ExternalLinkage, nullptr, "gas");
m_gas->setUnnamedAddr(true); // Address is not important
auto pt = m_builder.GetInsertPoint();
auto bb = m_builder.GetInsertBlock();
m_gasCheckFunc = llvm::Function::Create(llvm::FunctionType::get(Type::Void, Type::i256, false), llvm::Function::PrivateLinkage, "gas.check", _module);
auto gasCheckBB = llvm::BasicBlock::Create(_builder.getContext(), {}, m_gasCheckFunc);
m_builder.SetInsertPoint(gasCheckBB);
llvm::Value* cost = m_gasCheckFunc->arg_begin();
llvm::Value* gas = m_builder.CreateLoad(m_gas);
gas = m_builder.CreateSub(gas, cost);
m_builder.CreateStore(gas, m_gas);
m_builder.CreateRetVoid();
m_builder.SetInsertPoint(bb, pt);
}
void GasMeter::count(Instruction _inst)
{
if (!m_checkCall)
{
// Create gas check call with mocked block cost at begining of current cost-block
m_checkCall = m_builder.CreateCall(m_gasCheckFunc, llvm::UndefValue::get(Type::i256));
}
m_blockCost += getStepCost(_inst);
if (isCostBlockEnd(_inst))
commitCostBlock();
}
void GasMeter::commitCostBlock()
{
// If any uncommited block
if (m_checkCall)
{
if (m_blockCost > 0) // If any cost
m_checkCall->setArgOperand(0, m_builder.getIntN(256, m_blockCost)); // Update block cost in gas check call
else
m_checkCall->eraseFromParent(); // Remove the gas check call
m_checkCall = nullptr; // End cost-block
m_blockCost = 0;
}
assert(m_blockCost == 0);
}
void GasMeter::checkMemory(llvm::Value* _additionalMemoryInWords, llvm::IRBuilder<>& _builder)
{
// Memory uses other builder, but that can be changes later
auto cost = _builder.CreateMul(_additionalMemoryInWords, _builder.getIntN(256, static_cast<uint64_t>(c_memoryGas)), "memcost");
_builder.CreateCall(m_gasCheckFunc, cost);
}
}