--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/progs/while/compile.sc Mon Oct 26 10:24:59 2020 +0000
@@ -0,0 +1,258 @@
+// A Small Compiler for the WHILE Language
+// (it does not use a parser nor lexer)
+//
+// cal with
+//
+// amm compile.sc test
+// amm compile.sc test2
+
+
+// the abstract syntax trees
+abstract class Stmt
+abstract class AExp
+abstract class BExp
+type Block = List[Stmt]
+
+// statements
+case object Skip extends Stmt
+case class If(a: BExp, bl1: Block, bl2: Block) extends Stmt
+case class While(b: BExp, bl: Block) extends Stmt
+case class Assign(s: String, a: AExp) extends Stmt
+case class Write(s: String) extends Stmt
+case class Read(s: String) extends Stmt
+
+// arithmetic expressions
+case class Var(s: String) extends AExp
+case class Num(i: Int) extends AExp
+case class Aop(o: String, a1: AExp, a2: AExp) extends AExp
+
+// boolean expressions
+case object True extends BExp
+case object False extends BExp
+case class Bop(o: String, a1: AExp, a2: AExp) extends BExp
+
+
+// compiler headers needed for the JVM
+// (contains methods for read and write)
+val beginning = """
+.class public XXX.XXX
+.super java/lang/Object
+
+.method public static write(I)V
+ .limit locals 1
+ .limit stack 2
+ getstatic java/lang/System/out Ljava/io/PrintStream;
+ iload 0
+ invokevirtual java/io/PrintStream/println(I)V
+ return
+.end method
+
+.method public static read()I
+ .limit locals 10
+ .limit stack 10
+
+ ldc 0
+ istore 1 ; this will hold our final integer
+Label1:
+ getstatic java/lang/System/in Ljava/io/InputStream;
+ invokevirtual java/io/InputStream/read()I
+ istore 2
+ iload 2
+ ldc 10 ; the newline delimiter
+ isub
+ ifeq Label2
+ iload 2
+ ldc 32 ; the space delimiter
+ isub
+ ifeq Label2
+
+ iload 2
+ ldc 48 ; we have our digit in ASCII, have to subtract it from 48
+ isub
+ ldc 10
+ iload 1
+ imul
+ iadd
+ istore 1
+ goto Label1
+Label2:
+ ;when we come here we have our integer computed in local variable 1
+ iload 1
+ ireturn
+.end method
+
+.method public static main([Ljava/lang/String;)V
+ .limit locals 200
+ .limit stack 200
+
+; COMPILED CODE STARTS
+
+"""
+
+val ending = """
+; COMPILED CODE ENDS
+ return
+
+.end method
+"""
+
+// Compiler functions
+
+
+// for generating new labels
+var counter = -1
+
+def Fresh(x: String) = {
+ counter += 1
+ x ++ "_" ++ counter.toString()
+}
+
+// convenient string interpolations
+// for instructions and labels
+import scala.language.implicitConversions
+import scala.language.reflectiveCalls
+
+implicit def sring_inters(sc: StringContext) = new {
+ def i(args: Any*): String = " " ++ sc.s(args:_*) ++ "\n"
+ def l(args: Any*): String = sc.s(args:_*) ++ ":\n"
+}
+
+// this allows us to write things like
+// i"add" and l"Label"
+
+
+// environments
+type Env = Map[String, Int]
+
+
+def compile_op(op: String) = op match {
+ case "+" => i"iadd"
+ case "-" => i"isub"
+ case "*" => i"imul"
+}
+
+// arithmetic expression compilation
+def compile_aexp(a: AExp, env : Env) : String = a match {
+ case Num(i) => i"ldc $i"
+ case Var(s) => i"iload ${env(s)} \t\t; $s"
+ case Aop(op, a1, a2) =>
+ compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ compile_op(op)
+}
+
+// boolean expression compilation
+// - the jump-label is for where to jump if the condition is not true
+def compile_bexp(b: BExp, env : Env, jmp: String) : String = b match {
+ case True => ""
+ case False => i"goto $jmp"
+ case Bop("==", a1, a2) =>
+ compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ i"if_icmpne $jmp"
+ case Bop("!=", a1, a2) =>
+ compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ i"if_icmpeq $jmp"
+ case Bop("<", a1, a2) =>
+ compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ i"if_icmpge $jmp"
+}
+
+// statement compilation
+def compile_stmt(s: Stmt, env: Env) : (String, Env) = s match {
+ case Skip => ("", env)
+ case Assign(x, a) => {
+ val index = env.getOrElse(x, env.keys.size)
+ (compile_aexp(a, env) ++ i"istore $index \t\t; $x", env + (x -> index))
+ }
+ case If(b, bl1, bl2) => {
+ val if_else = Fresh("If_else")
+ val if_end = Fresh("If_end")
+ val (instrs1, env1) = compile_block(bl1, env)
+ val (instrs2, env2) = compile_block(bl2, env1)
+ (compile_bexp(b, env, if_else) ++
+ instrs1 ++
+ i"goto $if_end" ++
+ l"$if_else" ++
+ instrs2 ++
+ l"$if_end", env2)
+ }
+ case While(b, bl) => {
+ val loop_begin = Fresh("Loop_begin")
+ val loop_end = Fresh("Loop_end")
+ val (instrs1, env1) = compile_block(bl, env)
+ (l"$loop_begin" ++
+ compile_bexp(b, env, loop_end) ++
+ instrs1 ++
+ i"goto $loop_begin" ++
+ l"$loop_end", env1)
+ }
+ case Write(x) =>
+ (i"iload ${env(x)} \t\t; $x" ++
+ i"invokestatic XXX/XXX/write(I)V", env)
+ case Read(x) => {
+ val index = env.getOrElse(x, env.keys.size)
+ (i"invokestatic XXX/XXX/read()I" ++
+ i"istore $index \t\t; $x", env + (x -> index))
+ }
+}
+
+// compilation of a block (i.e. list of instructions)
+def compile_block(bl: Block, env: Env) : (String, Env) = bl match {
+ case Nil => ("", env)
+ case s::bl => {
+ val (instrs1, env1) = compile_stmt(s, env)
+ val (instrs2, env2) = compile_block(bl, env1)
+ (instrs1 ++ instrs2, env2)
+ }
+}
+
+// main compilation function for blocks
+def compile(bl: Block, class_name: String) : String = {
+ val instructions = compile_block(bl, Map.empty)._1
+ (beginning ++ instructions ++ ending).replaceAllLiterally("XXX", class_name)
+}
+
+
+
+
+
+// Fibonacci numbers as a bare-bone test-case
+val fib_test =
+ List(Assign("n", Num(9)), // n := 10;
+ Assign("minus1",Num(0)), // minus1 := 0;
+ Assign("minus2",Num(1)), // minus2 := 1;
+ Assign("temp",Num(0)), // temp := 0;
+ While(Bop("<",Num(0),Var("n")), // while n > 0 do {
+ List(Assign("temp",Var("minus2")), // temp := minus2;
+ Assign("minus2",Aop("+",Var("minus1"),Var("minus2"))),
+ // minus2 := minus1 + minus2;
+ Assign("minus1",Var("temp")), // minus1 := temp;
+ Assign("n",Aop("-",Var("n"),Num(1))))), // n := n - 1 };
+ Write("minus1")) // write minus1
+
+
+
+// prints out the JVM instructions
+@main
+def test() =
+ println(compile(fib_test, "fib"))
+
+
+
+
+// compiling and running .j-files
+//
+// JVM files can be assembled with
+//
+// java -jar jasmin.jar fib.j
+//
+// and started with
+//
+// java fib/fib
+
+
+def run(bl: Block, class_name: String) = {
+ val code = compile(bl, class_name)
+ os.write.over(os.pwd / s"$class_name.j", code)
+ os.proc("java", "-jar", "jasmin.jar", s"$class_name.j").call()
+ print(os.proc("java", s"$class_name/$class_name").call().out.string)
+}
+
+@main
+def test2() =
+ run(fib_test, "fib")