Decrement global gas value by instruction step cost

[#79942174]

evmcc/Compiler.cpp

@@ -8,6 +8,7 @@
 
 #include "Memory.h"
 #include "Ext.h"
+#include "GasMeter.h"
 
 namespace evmcc
 {
@@ -182,6 +183,7 @@ std::unique_ptr<llvm::Module> Compiler::compile(const dev::bytes& bytecode)
 	// Init runtime structures.
 	auto memory = Memory(builder, module.get());
 	auto ext = Ext(builder, module.get());
+	GasMeter gasMeter(builder, module.get());
 
 	// Jump to first instruction
 	builder.CreateBr(basicBlocks.begin()->second);
@@ -195,6 +197,8 @@ std::unique_ptr<llvm::Module> Compiler::compile(const dev::bytes& bytecode)
 		for (auto currentPC = basicBlock.begin(); currentPC != basicBlock.end(); ++currentPC)
 		{
 			auto inst = static_cast<Instruction>(bytecode[currentPC]);
+			gasMeter.check(inst);
+
 			switch (inst)
 			{
 

evmcc/GasMeter.cpp

@@ -1,6 +1,9 @@
 
 #include "GasMeter.h"
 
+#include <llvm/IR/GlobalVariable.h>
+#include <llvm/IR/Function.h>
+
 #include <libevmface/Instruction.h>
 #include <libevm/FeeStructure.h>
 
@@ -9,7 +12,7 @@ namespace evmcc
 
 using namespace dev::eth; // We should move all the JIT code into dev::eth namespace
 
-namespace
+namespace // Helper functions
 {
 
 uint64_t getStepCost(dev::eth::Instruction inst) // TODO: Add this function to FeeSructure
@@ -46,4 +49,21 @@ uint64_t getStepCost(dev::eth::Instruction inst) // TODO: Add this function to F
 
 }
 
+GasMeter::GasMeter(llvm::IRBuilder<>& _builder, llvm::Module* _module):
+	m_builder(_builder)
+{
+	m_gas = new llvm::GlobalVariable(*_module, m_builder.getIntNTy(256), false, llvm::GlobalVariable::PrivateLinkage, llvm::UndefValue::get(m_builder.getIntNTy(256)), "gas");
+	m_gas->setUnnamedAddr(true); // Address is not important
+
+	//llvm::Function::Create()
+}
+
+void GasMeter::check(Instruction _inst)
+{
+	auto stepCost = getStepCost(_inst);
+	auto before = m_builder.CreateLoad(m_gas, "gas.before");
+	auto after = m_builder.CreateSub(before, m_builder.getIntN(256, stepCost));
+	m_builder.CreateStore(after, m_gas);
+}
+
 }

evmcc/GasMeter.h

@@ -1,9 +1,26 @@
 
 #pragma once
 
+#include <llvm/IR/IRBuilder.h>
+
 #include <libevmface/Instruction.h>
 
 namespace evmcc
 {
 
+class GasMeter
+{
+public:
+	GasMeter(llvm::IRBuilder<>& _builder, llvm::Module* module);
+
+	GasMeter(const GasMeter&) = delete;
+	void operator=(GasMeter) = delete;
+
+	void check(dev::eth::Instruction _inst);
+
+private:
+	llvm::IRBuilder<>& m_builder;
+	llvm::GlobalVariable* m_gas;
+};
+
 }