ethminer/libevmjit/BasicBlock.h

#pragma once

#include <vector>

#include <llvm/IR/BasicBlock.h>

#include "Stack.h"

namespace dev
{
namespace eth
{
namespace jit
{

using ProgramCounter = uint64_t; // TODO: Rename
	
class BasicBlock
{
public:
	class LocalStack
	{
	public:

		/// 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);

		/// Synchronize current local stack with the EVM stack.
		void synchronize(Stack& _evmStack);

	private:

		LocalStack(llvm::IRBuilder<>& _builder, llvm::BasicBlock* _llvmBB);
		LocalStack(LocalStack const&) = delete;
		void operator=(LocalStack const&) = delete;
		friend BasicBlock;

		/// 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);

		std::vector<llvm::Value*>::iterator getItemIterator(size_t _index);

	private:

		llvm::BasicBlock* m_llvmBB;

		llvm::IRBuilder<>& m_builder;

		/**
		 *  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 current 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;

		/**
		 *  How many items higher is the current stack than the initial one.
		 *  May be negative.
		 */
		int m_tosOffset;

	};

	/// Basic block name prefix. The rest is beging instruction index.
	static const char* NamePrefix;

	explicit BasicBlock(ProgramCounter _beginInstIdx, ProgramCounter _endInstIdx, llvm::Function* _mainFunc, llvm::IRBuilder<>& _builder);
	explicit BasicBlock(std::string _name, llvm::Function* _mainFunc, llvm::IRBuilder<>& _builder);

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

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

	ProgramCounter begin() { return m_beginInstIdx; }
	ProgramCounter end() { return m_endInstIdx; }

	LocalStack& localStack() { return m_stack; }

	/// Optimization: propagates values between local stacks in basic blocks
	/// to avoid excessive pushing/popping on the EVM stack.
	static void linkLocalStacks(std::vector<BasicBlock*> _basicBlocks, llvm::IRBuilder<>& _builder);

	/// Prints local stack and block instructions to stderr.
	/// Useful for calling in a debugger session.
	void dump();
	void dump(std::ostream& os, bool _dotOutput = false);

private:
	ProgramCounter const m_beginInstIdx;
	ProgramCounter const m_endInstIdx;
	llvm::BasicBlock* const m_llvmBB;

	/// Basic black state vector (stack) - current/end values and their positions on stack
	/// @internal Must be AFTER m_llvmBB
	LocalStack m_stack;
};

}
}
}