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refactor: Remove redundant local variable declarations and streamline…
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… variable/parameter usage
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@bytexenon
bytexenon committed Jul 7, 2024
1 parent 1ebee91 commit b4f7c64
Showing 1 changed file with 45 additions and 65 deletions.
110 changes: 45 additions & 65 deletions the-tiny-lua-compiler.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -152,17 +152,17 @@ local TOKENIZER_LUA_OPERATORS = {

-- Maps escaped sequences to characters for string literals.
local TOKENIZER_ESCAPED_CHARACTER_CONVERSIONS = {
["a"] = "\a", -- bell
["b"] = "\b", -- backspace
["f"] = "\f", -- form feed
["n"] = "\n", -- newline
["r"] = "\r", -- carriage return
["t"] = "\t", -- horizontal tab
["v"] = "\v", -- vertical tab

[ "\\" ] = "\\", -- backslash
[ "\"" ] = "\"", -- double quote
[ "\'" ] = "\'", -- single quote
["a"] = "\a", -- bell
["b"] = "\b", -- backspace
["f"] = "\f", -- form feed
["n"] = "\n", -- newline
["r"] = "\r", -- carriage return
["t"] = "\t", -- horizontal tab
["v"] = "\v", -- vertical tab

["\\"] = "\\", -- backslash
["\""] = "\"", -- double quote
["\'"] = "\'", -- single quote
}

-- Lookup for Lua's boolean and nil constants.
Expand Down Expand Up @@ -230,7 +230,6 @@ function Tokenizer.tokenize(code)
charStream[charStreamLen] = char
end

local charStream = charStream
local curCharPos = 1
local curChar = charStream[curCharPos]

Expand All @@ -250,27 +249,27 @@ function Tokenizer.tokenize(code)

--// CHECKERS //--
local function isWhitespace(char)
local char = char or curChar
char = char or curChar
return char:match("%s")
end
local function isNumberStart(char)
local char = char or curChar
char = char or curChar
return char:match("%d")
end
local function isNumber(char)
local char = char or curChar
char = char or curChar
return char:match("%d")
end
local function isIdentifier(char)
local char = char or curChar
char = char or curChar
return char:match("[%a%d_]")
end
local function isIdentifierStart(char)
local char = char or curChar
char = char or curChar
return char:match("[%a_]")
end
local function isScientificNotationPrefix(char)
local char = char or curChar
char = char or curChar
return char == "e" or char == "E"
end
local function isHexadecimalNumberPrefix()
Expand Down Expand Up @@ -469,7 +468,6 @@ function Tokenizer.tokenize(code)

--// TOKENIZERS //--
local function getNextToken()
local curChar = curChar
if isWhitespace(curChar) then
consumeWhitespace()
return
Expand All @@ -488,7 +486,7 @@ function Tokenizer.tokenize(code)
return { TYPE = "Constant", Value = identifier }
end
return { TYPE = "Identifier", Value = identifier }
elseif isString(curChar) then
elseif isString() then
return { TYPE = "String", Value = consumeString() }
elseif isVarArg() then
consume(2)
Expand Down Expand Up @@ -573,7 +571,6 @@ local PARSER_LUA_BINARY_OPERATORS = createLookupTable({ "+", "-", "*", "/",

local Parser = {}
function Parser.parse(tokens)
local tokens = tokens
local currentToken = tokens[1]
local currentTokenIndex = 1
local scopeStack = {}
Expand Down Expand Up @@ -633,13 +630,13 @@ function Parser.parse(tokens)

--// TOKEN CHECKERS //--
local function checkCharacter(character, token)
local token = token or currentToken
token = token or currentToken
return token
and token.TYPE == "Character"
and token.Value == character
end
local function checkKeyword(keyword, token)
local token = token or currentToken
token = token or currentToken
return token
and token.TYPE == "Keyword"
and token.Value == keyword
Expand All @@ -665,13 +662,6 @@ function Parser.parse(tokens)
end

--// EXPECTORS //--
local function expectToken(expectedType, expectedValue, skipConsume)
local actualType = currentToken and currentToken.TYPE or "nil"
assert(currentToken and currentToken.TYPE == expectedType, "Expected a " .. expectedType .. ", got: " .. actualType)
assert(currentToken.Value == expectedValue, "Expected '" .. expectedValue .. "'")
if not skipConsume then consume() end
return currentToken
end
local function expectTokenType(expectedType, skipConsume)
local actualType = currentToken and currentToken.TYPE or "nil"
assert(actualType == expectedType, string.format("Expected a %s, got: %s", expectedType, actualType))
Expand Down Expand Up @@ -912,8 +902,8 @@ function Parser.parse(tokens)
end
return nil
end
function parsePrefixExpression(precedence)
local primaryExpression = parsePrimaryExpression(precedence) -- <primary>
function parsePrefixExpression()
local primaryExpression = parsePrimaryExpression() -- <primary>
if not primaryExpression then return end

-- <suffix>*
Expand All @@ -929,7 +919,7 @@ function Parser.parse(tokens)
local unaryOperator = currentToken
-- <unary> ::= <unary operator> <unary> | <primary>
if not isUnaryOperator(currentToken) then
return parsePrefixExpression(PARSER_UNARY_OPERATOR_PRECEDENCE)
return parsePrefixExpression()
end

-- <unary operator> <unary>
Expand All @@ -939,7 +929,7 @@ function Parser.parse(tokens)
end
function parseBinaryExpression(minPrecedence)
-- <binary> ::= <unary> <binary operator> <binary> | <unary>
local minPrecedence = minPrecedence or 0
minPrecedence = minPrecedence or 0
local expression = parseUnaryOperator() -- <unary>
if not expression then return end

Expand Down Expand Up @@ -1274,7 +1264,7 @@ function InstructionGenerator.generate(ast)
local currentProto
local takenRegisters, code, constants,
constantLookup, upvalues, upvalueLookup,
protos, numParams, isVarArg, functionName
protos

--// PROTO MANAGEMENT //--
local function setProto(proto)
Expand All @@ -1286,9 +1276,6 @@ function InstructionGenerator.generate(ast)
upvalues = proto.upvalues
upvalueLookup = proto.upvalueLookup
protos = proto.protos
numParams = proto.numParams
isVarArg = proto.isVarArg
functionName = proto.functionName
end
local function newProto()
currentProto = {
Expand Down Expand Up @@ -1382,7 +1369,7 @@ function InstructionGenerator.generate(ast)
end
local function exitScope()
table.remove(scopes)
for variableName, register in pairs(currentScope.locals) do
for variableName in pairs(currentScope.locals) do
unregisterVariable(variableName)
end
if #scopes > 0 then
Expand Down Expand Up @@ -1468,7 +1455,7 @@ function InstructionGenerator.generate(ast)
addInstruction("CALL", expressionRegister, argumentAmount, returnAmount)
deallocateRegisters(argumentRegisters)
local returnRegisters = { expressionRegister }
for index = expressionRegister + 1, expressionRegister + node.ReturnValueAmount - 1 do
for _ = expressionRegister + 1, expressionRegister + node.ReturnValueAmount - 1 do
table.insert(returnRegisters, allocateRegister())
end
return unpack(returnRegisters)
Expand Down Expand Up @@ -1497,7 +1484,7 @@ function InstructionGenerator.generate(ast)
addInstruction("CALL", expressionRegister, argumentAmount, returnAmount)
deallocateRegisters(argumentRegisters)
local returnRegisters = { expressionRegister }
for index = expressionRegister + 1, expressionRegister + node.ReturnValueAmount - 1 do
for _ = expressionRegister + 1, expressionRegister + node.ReturnValueAmount - 1 do
table.insert(returnRegisters, allocateRegister())
end
return unpack(returnRegisters)
Expand All @@ -1520,7 +1507,7 @@ function InstructionGenerator.generate(ast)
-- OP_VARARG [A, B] R(A), R(A+1), ..., R(A+B-1) = vararg
addInstruction("VARARG", expressionRegister, returnAmount)
local returnRegisters = { expressionRegister }
for index = expressionRegister + 1, expressionRegister + node.ReturnValueAmount - 1 do
for _ = expressionRegister + 1, expressionRegister + node.ReturnValueAmount - 1 do
table.insert(returnRegisters, allocateRegister())
end
return unpack(returnRegisters)
Expand All @@ -1534,7 +1521,6 @@ function InstructionGenerator.generate(ast)
return expressionRegister
end
local function compileTableNode(node, expressionRegister)
local elements = node.Elements
local implicitElements = node.ImplicitElements
local explicitElements = node.ExplicitElements
local sizeB = math.min(#implicitElements, 255)
Expand Down Expand Up @@ -1633,7 +1619,7 @@ function InstructionGenerator.generate(ast)
end

--// STATEMENT COMPILERS //--
local function compileBreakStatementNode(node)
local function compileBreakStatementNode()
-- OP_JMP [A, sBx] pc+=sBx
local jumpInstructionIndex = addInstruction("JMP", 0, 0)
table.insert(breakInstructions, jumpInstructionIndex)
Expand Down Expand Up @@ -1673,7 +1659,6 @@ function InstructionGenerator.generate(ast)
local localRegister = findVariableRegister(variableName)
processFunction(node, localRegister, variableName)
elseif expression.VariableType == "Upvalue" then
local upvalueIndex = findOrCreateUpvalue(variableName)
local closureRegister = allocateRegister()
processFunction(node, closureRegister, variableName)
-- OP_SETUPVAL [A, B] UpValue[B] := R(A)
Expand Down Expand Up @@ -1754,7 +1739,7 @@ function InstructionGenerator.generate(ast)
error("Expected 3 expression registers")
end
local loopStart = #code
for index, iteratorVariable in ipairs(iteratorVariables) do
for _, iteratorVariable in ipairs(iteratorVariables) do
local iteratorRegister = allocateRegister()
registerVariable(iteratorVariable, iteratorRegister)
end
Expand Down Expand Up @@ -1878,7 +1863,7 @@ function InstructionGenerator.generate(ast)

--// CODE GENERATION //--
function processExpressionNode(node, expressionRegister)
local expressionRegister = expressionRegister or allocateRegister()
expressionRegister = expressionRegister or allocateRegister()
local nodeType = node.TYPE
while nodeType == "Expression" do
node = node.Value
Expand All @@ -1905,7 +1890,7 @@ function InstructionGenerator.generate(ast)
local nodeType = node.TYPE
if nodeType == "FunctionCall" or nodeType == "MethodCall" then
return deallocateRegisters({ processExpressionNode(node) })
elseif nodeType == "BreakStatement" then return compileBreakStatementNode(node)
elseif nodeType == "BreakStatement" then return compileBreakStatementNode()
elseif nodeType == "LocalFunctionDeclaration" then return compileLocalFunctionDeclarationNode(node)
elseif nodeType == "FunctionDeclaration" then return compileFunctionDeclarationNode(node)
elseif nodeType == "LocalDeclaration" then return compileLocalDeclarationNode(node)
Expand Down Expand Up @@ -1933,7 +1918,7 @@ function InstructionGenerator.generate(ast)
end
function processCodeBlock(list)
enterScope()
for index, node in ipairs(list) do
for _, node in ipairs(list) do
processStatementNode(node)
end
exitScope()
Expand All @@ -1943,22 +1928,20 @@ function InstructionGenerator.generate(ast)
for _, parameter in ipairs(parameters) do
registerVariable(parameter, allocateRegister())
end
for index, node in ipairs(list) do
for _, node in ipairs(list) do
processStatementNode(node)
end
exitScope()
end
function processFunction(node, expressionRegister, name)
local codeBlock = node.Codeblock
local parameters = node.Parameters
local parameters = node.Parameters or {}
local isVarArg = node.IsVarArg
local oldProto = currentProto
local proto = newProto()
local parameters = parameters or {}
local name = (name and "@" .. name) or "@anonymous"
proto.numParams = #parameters
proto.isVarArg = isVarArg
proto.functionName = name
proto.functionName = (name and "@" .. name) or "@anonymous"

processFunctionCodeBlock(codeBlock, parameters)

Expand All @@ -1969,7 +1952,7 @@ function InstructionGenerator.generate(ast)
-- R(A) := closure(KPROTO[Bx], R(A), ... ,R(A+n))
addInstruction("CLOSURE", expressionRegister, #protos - 1)

for index, upvalueName in ipairs(proto.upvalues) do
for _, upvalueName in ipairs(proto.upvalues) do
local upvalueType = getVariableType(upvalueName)
if upvalueType == "Local" then
-- OP_MOVE [A, B] R(A) := R(B)
Expand Down Expand Up @@ -2032,10 +2015,10 @@ local COMPILER_OPCODE_LOOKUP = {
--]]

local Compiler = {}
function Compiler.compile(proto)
function Compiler.compile(mainProto)
--// BYTE MANIPULATION (needed for compiling to bytecode) //--
local function twosComplement(value)
local value = value or 0
value = value or 0
return math.max(value, -value - 1)
end
local function makeBytes(value, byteCount)
Expand All @@ -2049,9 +2032,6 @@ function Compiler.compile(proto)
local function makeOneByte(value)
return string.char(value % 256)
end
local function makeTwoBytes(value)
return makeBytes(value, 2)
end
local function makeFourBytes(value)
return makeBytes(value, 4)
end
Expand All @@ -2067,7 +2047,7 @@ function Compiler.compile(proto)
elseif value == 1/0 then -- infinity
mantissa, exponent = 0, 2047
else
mantissa = (mantissa * 2 - 1) * math.ldexp(0.5, 53)
mantissa = (mantissa * 2 - 1) * (0.5 * (2 ^ 53))
exponent = exponent + 1022
end

Expand All @@ -2088,7 +2068,7 @@ function Compiler.compile(proto)
local makeString, makeConstant, makeInstruction, makeConstantSection,
makeCodeSection, makeFunction, makeHeader
function makeString(value)
local value = value .. "\0"
value = value .. "\0"
local size = makeEightBytes(#value)
return size .. value
end
Expand Down Expand Up @@ -2132,8 +2112,8 @@ function Compiler.compile(proto)
constantSection = constantSection .. makeConstant(constant, constantType)
end
constantSection = constantSection .. makeFourBytes(#proto.protos) -- Number of protos
for _, proto in ipairs(proto.protos) do
constantSection = constantSection .. makeFunction(proto)
for _, childProto in ipairs(proto.protos) do
constantSection = constantSection .. makeFunction(childProto)
end
return constantSection
end
Expand Down Expand Up @@ -2175,7 +2155,7 @@ function Compiler.compile(proto)
--// MAIN //--
local function compile()
local header = makeHeader()
local functionHeader = makeFunction(proto)
local functionHeader = makeFunction(mainProto)
return header .. functionHeader
end

Expand Down

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