Give back an amount of gas not used by CALL instructions

[#79942174]

evmcc/Compiler.cpp

@@ -786,6 +786,7 @@ std::unique_ptr<llvm::Module> Compiler::compile(const dev::bytes& bytecode)
 
 				gasMeter.commitCostBlock(gas);
 				auto ret = ext.call(gas, receiveAddress, value, inOff, inSize, outOff, outSize);
+				gasMeter.giveBack(gas);
 				stack.push(ret);
 				break;
 			}

evmcc/Ext.cpp

@@ -165,7 +165,7 @@ Value* Ext::create(llvm::Value* _endowment, llvm::Value* _initOff, llvm::Value*
 	return address;
 }
 
-llvm::Value* Ext::call(llvm::Value* _gas, llvm::Value* _receiveAddress, llvm::Value* _value, llvm::Value* _inOff, llvm::Value* _inSize, llvm::Value* _outOff, llvm::Value* _outSize)
+llvm::Value* Ext::call(llvm::Value*& _gas, llvm::Value* _receiveAddress, llvm::Value* _value, llvm::Value* _inOff, llvm::Value* _inSize, llvm::Value* _outOff, llvm::Value* _outSize)
 {
 	m_builder.CreateStore(_gas, m_args[0]);
 	auto receiveAddress = bswap(_receiveAddress); // to BE
@@ -177,6 +177,7 @@ llvm::Value* Ext::call(llvm::Value* _gas, llvm::Value* _receiveAddress, llvm::Va
 	m_builder.CreateStore(_outSize, m_arg7);
 	llvm::Value* args[] = {m_args[0], m_arg2, m_arg3, m_arg4, m_arg5, m_arg6, m_arg7, m_args[1]};
 	m_builder.CreateCall(m_call, args);
+	_gas = m_builder.CreateLoad(m_args[0]); // Return gas
 	return m_builder.CreateLoad(m_args[1]);
 }
 
@@ -284,10 +285,10 @@ EXPORT void ext_call(i256* _gas, h256* _receiveAddress, i256* _value, i256* _inO
 	auto value = llvm2eth(*_value);
 
 	auto ret = false;
+	auto gas = llvm2eth(*_gas);
 	if (ext.balance(ext.myAddress) >= value)
 	{
 		ext.subBalance(value);
-		auto gas = llvm2eth(*_gas);
 		auto receiveAddress = dev::right160(*_receiveAddress);
 		auto inOff = static_cast<size_t>(llvm2eth(*_inOff));
 		auto inSize = static_cast<size_t>(llvm2eth(*_inSize));
@@ -299,7 +300,7 @@ EXPORT void ext_call(i256* _gas, h256* _receiveAddress, i256* _value, i256* _inO
 		auto ret = ext.call(receiveAddress, value, inRef, &gas, outRef, onOp, {}, receiveAddress);
 	}
 
-	// m_gas += gas; // TODO: Handle gas
+	*_gas = eth2llvm(gas);
 	_ret->a = ret ? 1 : 0;
 }
 

evmcc/Ext.h

@@ -36,7 +36,7 @@ public:
 	void suicide(llvm::Value* _address);
 	llvm::Value* calldataload(llvm::Value* _index);
 	llvm::Value* create(llvm::Value* _endowment, llvm::Value* _initOff, llvm::Value* _initSize);
-	llvm::Value* call(llvm::Value* _gas, llvm::Value* _receiveAddress, llvm::Value* _value, llvm::Value* _inOff, llvm::Value* _inSize, llvm::Value* _outOff, llvm::Value* _outSize);
+	llvm::Value* call(llvm::Value*& _gas, llvm::Value* _receiveAddress, llvm::Value* _value, llvm::Value* _inOff, llvm::Value* _inSize, llvm::Value* _outOff, llvm::Value* _outSize);
 
 	llvm::Value* sha3(llvm::Value* _inOff, llvm::Value* _inSize);
 	llvm::Value* exp(llvm::Value* _left, llvm::Value* _right);

evmcc/GasMeter.cpp

@@ -108,6 +108,13 @@ void GasMeter::count(Instruction _inst)
 		commitCostBlock();
 }
 
+void GasMeter::giveBack(llvm::Value* _gas)
+{
+	llvm::Value* gasCounter = m_builder.CreateLoad(m_gas, "gas");
+	gasCounter = m_builder.CreateAdd(gasCounter, _gas);
+	m_builder.CreateStore(gasCounter, m_gas);
+}
+
 void GasMeter::commitCostBlock(llvm::Value* _additionalCost)
 {
 	assert(!_additionalCost || m_checkCall); // _additionalCost => m_checkCall; Must be inside cost-block

evmcc/GasMeter.h

@@ -23,6 +23,9 @@ public:
 	/// @param _additionalCost adds additional cost to cost-block before commit
 	void commitCostBlock(llvm::Value* _additionalCost = nullptr);
 
+	/// Give back an amount of gas not used by a call
+	void giveBack(llvm::Value* _gas);
+
 	/// Generate code that checks the cost of additional memory used by program
 	void checkMemory(llvm::Value* _additionalMemoryInWords, llvm::IRBuilder<>& _builder);