--- /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"))