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(ns cljcc.tacky
(:require
[clojure.pprint :as pp]
[cljcc.lexer :as l]
[cljcc.parser :as p]))
(def counter "Global integer counter for generating unique identifier names." (atom 0))
(defn create-identifier
"Returns a unique identifier. Used for generating tacky variable names."
([]
(create-identifier "tmp"))
([identifier]
(let [n @counter
_ (swap! counter #(+ % 1))]
(str identifier "." n))))
(defn variable
([]
{:type :variable
:value (create-identifier)})
([^String identifier]
{:type :variable
:value (create-identifier identifier)}))
(defn constant-instruction [^Integer v]
{:type :constant
:value v})
(defn- unary-operator [^String unop]
(condp = unop
"~" :complement
"-" :negate))
(defn- binary-operator [binop]
(condp = binop
:add-exp :add
:sub-exp :sub
:mul-exp :mul
:div-exp :div
:mod-exp :mod
:bit-and-exp :bit-and
:bit-or-exp :bit-or
:bit-xor-exp :bit-xor
:bit-right-shift-exp :bit-right-shift
:bit-left-shift-exp :bit-left-shift))
(defn- unary-instruction [unary-operator src dst]
{:type :unary
:unary-operator unary-operator
:dst dst
:src src})
(defn- binary-instruction [binary-operator src1 src2 dst]
{:type :binary
:binary-operator binary-operator
:src1 src1
:src2 src2
:dst dst})
(defn return-instruction [val]
{:type :return
:val val})
(def binary-exprs
#{:add-exp
:sub-exp
:mul-exp
:mod-exp
:div-exp
:bit-and-exp
:bit-or-exp
:bit-xor-exp
:bit-right-shift-exp
:bit-left-shift-exp})
(defn- binary-expr? [v]
(contains? binary-exprs v))
(declare expression-handler)
(defn- constant-expr-handler [e]
{:val (constant-instruction (:value e))})
(defn- unary-expr-handler [e]
(let [inner (expression-handler (:value e))
dst (variable)
src (:val inner)
unary-operator (:unary-operator e)
instruction (unary-instruction unary-operator src dst)]
{:val dst
:instructions (flatten [(:instructions inner) instruction])}))
(defn- binary-expr-handler [e]
(let [e1 (expression-handler (nth e 1))
e2 (expression-handler (nth e 2))
src1 (:val e1)
src2 (:val e2)
dst (variable)
binary-operator (binary-operator (first e))
instruction (binary-instruction binary-operator src1 src2 dst)]
{:val dst
:instructions (flatten [(:instructions e1) (:instructions e2) instruction])}))
(defn- expression-handler [e]
(when-let [exp-type (:exp-type e)]
(cond
(= exp-type :constant-exp) (constant-expr-handler e)
(= exp-type :unary-exp) (unary-expr-handler e)
(binary-expr? exp-type) (binary-expr-handler e))))
(defn- exp-instructions [exp]
(expression-handler exp))
(defn- ret-instructions [exp]
(let [e (exp-instructions exp)
val (:val e)
instructions (:instructions e)]
(conj (vec instructions) (return-instruction val))))
(defn ast-statement->tacky-instructions [statement]
(remove nil? (ret-instructions (:value statement))))
(defn tacky-generate [ast]
(reset! counter 0)
(map (fn [f]
(-> f
(assoc :instructions (flatten (map ast-statement->tacky-instructions (:statements f))))
(dissoc :statements)))
ast))
(comment
(reset! counter 0)
(pp/pprint
(tacky-generate
(p/parse (l/lex "int main(void) {return -(~1);}"))))
(pp/pprint
(tacky-generate
(p/parse "int main(void) {return 1 * 2 & 3 * (4 + 5);}")))
(pp/pprint
(p/parse "int main(void) {return 1 * 2 - 3 * (4 + 5);}"))
(pp/pprint
(p/parse "int main(void) {return 1 + 2 + -3 + -(4 + 5);}"))
(pp/pprint
(tacky-generate
(p/parse "int main(void) {return 1 + 2 + -3 + -(4 + 5);}")))
())
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