ethminer/evmjit/libevmjit/BasicBlock.h

#pragma once

#include <vector>

#include "Common.h"
#include "Stack.h"

namespace dev
{
namespace eth
{
namespace jit
{
using namespace evmjit;
using instr_idx = uint64_t;

class BasicBlock;

class LocalStack
{
public:
	explicit LocalStack(Stack& _globalStack);
	LocalStack(LocalStack const&) = delete;
	void operator=(LocalStack const&) = delete;

	/// Pushes value on stack
	void push(llvm::Value* _value);

	/// Pops and returns top value
	llvm::Value* pop();

	/// Duplicates _index'th value on stack
	void dup(size_t _index);

	/// Swaps _index'th value on stack with a value on stack top.
	/// @param _index Index of value to be swaped. Must be > 0.
	void swap(size_t _index);

	ssize_t size() const { return static_cast<ssize_t>(m_currentStack.size()) - static_cast<ssize_t>(m_globalPops); }
	ssize_t minSize() const { return m_minSize; }
	ssize_t maxSize() const { return m_maxSize; }

	/// Finalize local stack: check the requirements and update of the global stack.
	void finalize(llvm::IRBuilder<>& _builder, llvm::BasicBlock& _bb);

private:
	/// Gets _index'th value from top (counting from 0)
	llvm::Value* get(size_t _index);

	/// Sets _index'th value from top (counting from 0)
	void set(size_t _index, llvm::Value* _value);

	/// This stack contains LLVM values that correspond to items found at
	/// the EVM stack when the current basic block starts executing.
	/// Location 0 corresponds to the top of the EVM stack, location 1 is
	/// the item below the top and so on. The stack grows as the code
	/// accesses more items on the EVM stack but once a value is put on
	/// the stack, it will never be replaced.
	std::vector<llvm::Value*> m_initialStack;

	/// This stack tracks the contents of the EVM stack as the basic block
	/// executes. It may grow on both sides, as the code pushes items on
	/// top of the stack or changes existing items.
	std::vector<llvm::Value*> m_currentStack;

	Stack& m_global;			///< Reference to global stack.

	size_t m_globalPops = 0; 	///< Number of items poped from global stack. In other words: global - local stack overlap.
	ssize_t m_minSize = 0;		///< Minimum reached local stack size. Can be negative.
	ssize_t m_maxSize = 0; 		///< Maximum reached local stack size.
};

class BasicBlock
{
public:
	explicit BasicBlock(instr_idx _firstInstrIdx, code_iterator _begin, code_iterator _end, llvm::Function* _mainFunc, bool isJumpDest);

	BasicBlock(const BasicBlock&) = delete;
	BasicBlock& operator=(const BasicBlock&) = delete;

	llvm::BasicBlock* llvm() { return m_llvmBB; }

	instr_idx firstInstrIdx() const { return m_firstInstrIdx; }
	code_iterator begin() const { return m_begin; }
	code_iterator end() const { return m_end; }

	bool isJumpDest() const { return m_isJumpDest; }

private:
	instr_idx const m_firstInstrIdx = 0; 	///< Code index of first instruction in the block
	code_iterator const m_begin = {};			///< Iterator pointing code beginning of the block
	code_iterator const m_end = {};				///< Iterator pointing code end of the block

	llvm::BasicBlock* const m_llvmBB;

	/// Is the basic block a valid jump destination.
	/// JUMPDEST is the first instruction of the basic block.
	bool const m_isJumpDest = false;
};

}
}
}