diff -r 5d860ff01938 -r fc2e3609d5e5 progs/fun/fun.sc --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/progs/fun/fun.sc Mon Jul 20 10:06:43 2020 +0100 @@ -0,0 +1,201 @@ +// A Small Compiler for a Simple Functional Language +// (it does not include a parser and lexer) +// +// call with +// +// amm fun.sc +// +// this will print out the JVM instructions for two +// factorial functions + + +// abstract syntax trees +abstract class Exp +abstract class BExp +abstract class Decl + +// functions and declarations +case class Def(name: String, args: List[String], body: Exp) extends Decl +case class Main(e: Exp) extends Decl + +// expressions +case class Call(name: String, args: List[Exp]) extends Exp +case class If(a: BExp, e1: Exp, e2: Exp) extends Exp +case class Write(e: Exp) extends Exp +case class Var(s: String) extends Exp +case class Num(i: Int) extends Exp +case class Aop(o: String, a1: Exp, a2: Exp) extends Exp +case class Sequ(e1: Exp, e2: Exp) extends Exp + +// boolean expressions +case class Bop(o: String, a1: Exp, a2: Exp) extends BExp + +// calculating the maximal needed stack size +def max_stack_exp(e: Exp): Int = e match { + case Call(_, args) => args.map(max_stack_exp).sum + case If(a, e1, e2) => + max_stack_bexp(a) + (List(max_stack_exp(e1), max_stack_exp(e2)).max) + case Write(e) => max_stack_exp(e) + 1 + case Var(_) => 1 + case Num(_) => 1 + case Aop(_, a1, a2) => max_stack_exp(a1) + max_stack_exp(a2) + case Sequ(e1, e2) => List(max_stack_exp(e1), max_stack_exp(e2)).max +} +def max_stack_bexp(e: BExp): Int = e match { + case Bop(_, a1, a2) => max_stack_exp(a1) + max_stack_exp(a2) +} + +// compiler - built-in functions +// copied from http://www.ceng.metu.edu.tr/courses/ceng444/link/jvm-cpm.html +// + +val library = """ +.class public XXX.XXX +.super java/lang/Object + +.method public static write(I)V + .limit locals 5 + .limit stack 5 + iload 0 + getstatic java/lang/System/out Ljava/io/PrintStream; + swap + invokevirtual java/io/PrintStream/println(I)V + return +.end method + +""" + +// for generating new labels +var counter = -1 + +def Fresh(x: String) = { + counter += 1 + x ++ "_" ++ counter.toString() +} + +// convenient string interpolations for +// generating instructions, labels etc +import scala.language.implicitConversions +import scala.language.reflectiveCalls + +// convenience for code-generation (string interpolations) +implicit def sring_inters(sc: StringContext) = new { + def i(args: Any*): String = " " ++ sc.s(args:_*) ++ "\n" // instructions + def l(args: Any*): String = sc.s(args:_*) ++ ":\n" // labels + def m(args: Any*): String = sc.s(args:_*) ++ "\n" // methods +} + +// variable / index environments +type Env = Map[String, Int] + +// compile expressions +def compile_exp(a: Exp, env : Env) : String = a match { + case Num(i) => i"ldc $i" + case Var(s) => i"iload ${env(s)}" + case Aop("+", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"iadd" + case Aop("-", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"isub" + case Aop("*", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"imul" + case Aop("/", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"idiv" + case Aop("%", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"irem" + case If(b, a1, a2) => { + val if_else = Fresh("If_else") + val if_end = Fresh("If_end") + compile_bexp(b, env, if_else) ++ + compile_exp(a1, env) ++ + i"goto $if_end" ++ + l"$if_else" ++ + compile_exp(a2, env) ++ + l"$if_end" + } + case Call(name, args) => { + val is = "I" * args.length + args.map(a => compile_exp(a, env)).mkString ++ + i"invokestatic XXX/XXX/$name($is)I" + } + case Sequ(a1, a2) => { + compile_exp(a1, env) ++ i"pop" ++ compile_exp(a2, env) + } + case Write(a1) => { + compile_exp(a1, env) ++ + i"dup" ++ + i"invokestatic XXX/XXX/write(I)V" + } +} + +// compile boolean expressions +def compile_bexp(b: BExp, env : Env, jmp: String) : String = b match { + case Bop("==", a1, a2) => + compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpne $jmp" + case Bop("!=", a1, a2) => + compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpeq $jmp" + case Bop("<", a1, a2) => + compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpge $jmp" + case Bop("<=", a1, a2) => + compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpgt $jmp" +} + +// compile functions and declarations +def compile_decl(d: Decl) : String = d match { + case Def(name, args, a) => { + val env = args.zipWithIndex.toMap + val is = "I" * args.length + m".method public static $name($is)I" ++ + m".limit locals ${args.length.toString}" ++ + m".limit stack ${1 + max_stack_exp(a)}" ++ + l"${name}_Start" ++ + compile_exp(a, env) ++ + i"ireturn" ++ + m".end method\n" + } + case Main(a) => { + m".method public static main([Ljava/lang/String;)V" ++ + m".limit locals 200" ++ + m".limit stack 200" ++ + compile_exp(a, Map()) ++ + i"invokestatic XXX/XXX/write(I)V" ++ + i"return" ++ + m".end method\n" + } +} + +// the main compilation function +def compile(prog: List[Decl], class_name: String) : String = { + val instructions = prog.map(compile_decl).mkString + (library + instructions).replaceAllLiterally("XXX", class_name) +} + + + + +// An example program (two versions of factorial) +// +// def fact(n) = +// if n == 0 then 1 else n * fact(n - 1); +// +// def facT(n, acc) = +// if n == 0 then acc else facT(n - 1, n * acc); +// +// fact(10) ; facT(10, 1) +// + + +val test_prog = + List(Def("fact", List("n"), + If(Bop("==",Var("n"),Num(0)), + Num(1), + Aop("*",Var("n"), + Call("fact",List(Aop("-",Var("n"),Num(1))))))), + + Def("facT",List("n", "acc"), + If(Bop("==",Var("n"),Num(0)), + Var("acc"), + Call("facT",List(Aop("-",Var("n"),Num(1)), + Aop("*",Var("n"),Var("acc")))))), + + Main(Sequ(Write(Call("fact",List(Num(10)))), + Write(Call("facT",List(Num(10), Num(1))))))) + +// prints out the JVM instructions +@main +def test() = + println(compile(test_prog, "fact"))