doc frontend and refactor

Author: paulzfm

src/main/scala/decaf/Main.scala

@@ -3,5 +3,6 @@ package decaf
 import decaf.driver.Launcher
 
 object Main {
+
   def main(args: Array[String]): Unit = Launcher.withArgs(args)
 }

src/main/scala/decaf/backend/asm/Asm.scala

@@ -18,8 +18,15 @@ import decaf.util.Conversions._
   * @param emitter  helper assembly code emitter
   * @param regAlloc register allocator
   */
-class Asm(val emitter: AsmEmitter, val regAlloc: RegAlloc) extends Phase[TacProg, String]("asm: " + emitter) {
+class Asm(val emitter: AsmEmitter, val regAlloc: RegAlloc)(implicit config: Config)
+  extends Phase[TacProg, String]("asm: " + emitter, config) {
 
+  /**
+    * Transformer entry.
+    *
+    * @param prog a TAC program
+    * @return a string representing the emitted assembly code
+    */
   override def transform(prog: TacProg): String = {
     Log.info("phase: asm")
     val analyzer = new LivenessAnalyzer[PseudoInstr]
@@ -42,7 +49,12 @@ class Asm(val emitter: AsmEmitter, val regAlloc: RegAlloc) extends Phase[TacProg
     emitter.emitEnd()
   }
 
-  override def onSucceed(code: String)(implicit config: Config): Unit = {
+  /**
+    * After emitting the assembly code, output it to file.
+    *
+    * @param code assembly code
+    */
+  override def onSucceed(code: String): Unit = {
     if (config.target.equals(Config.Target.PA5)) {
       val path = config.dstDir / config.sourceBaseName + ".s"
       val printer = new PrintWriter(path)

src/main/scala/decaf/backend/asm/AsmEmitter.scala

@@ -4,7 +4,6 @@ import decaf.lowlevel.AsmCodePrinter
 import decaf.lowlevel.instr.{PseudoInstr, Reg}
 import decaf.lowlevel.tac.{TacFunc, VTable}
 
-
 /**
   * Emit assembly code.
   *
@@ -13,6 +12,7 @@ import decaf.lowlevel.tac.{TacFunc, VTable}
   * @param callerSaveRegs  platform-specific registers that need be saved by caller.
   */
 abstract class AsmEmitter(val platformName: String, val allocatableRegs: Array[Reg], val callerSaveRegs: Array[Reg]) {
+
   /**
     * Emit assembly code for a virtual table.
     *

src/main/scala/decaf/backend/asm/Holes.scala

@@ -11,10 +11,12 @@ import decaf.lowlevel.instr.{PseudoInstr, Temp}
 object Holes {
 
   object CallerSave extends PseudoInstr(new Array[Temp](0), new Array[Temp](0)) {
+
     override def toString: String = "# TODO: caller save"
   }
 
   object CallerRestore extends PseudoInstr(new Array[Temp](0), new Array[Temp](0)) {
+
     override def toString: String = "# TODO: caller restore"
   }
 

src/main/scala/decaf/backend/asm/SubroutineEmitter.scala

@@ -11,6 +11,7 @@ import decaf.lowlevel.label.Label
   * @param info    basic info of this subroutine
   */
 abstract class SubroutineEmitter protected(val emitter: AsmEmitter, var info: SubroutineInfo) {
+
   /**
     * Append an assembly instruction that stores the value of a register to stack.
     *

src/main/scala/decaf/backend/asm/mips/MipsAsmEmitter.scala

@@ -10,7 +10,6 @@ import decaf.util.Conversions._
 
 import scala.collection.mutable
 
-
 /**
   * Emit MIPS assembly code.
   */
@@ -24,7 +23,9 @@ final class MipsAsmEmitter extends AsmEmitter("mips", Mips.allocatableRegs, Mips
       val parent = vtbl.parent.get
       printer.println(".word %s    # parent: %s", parent.label, parent.className)
     }
-    else printer.println(".word 0    # parent: none")
+    else {
+      printer.println(".word 0    # parent: none")
+    }
     val index = pool.add(vtbl.className)
     printer.println(".word %s%d    # class name", STR_PREFIX, index)
     vtbl.getItems.forEach { entry =>
@@ -149,6 +150,7 @@ final class MipsAsmEmitter extends AsmEmitter("mips", Mips.allocatableRegs, Mips
   }
 
   private class MipsInstrSelector private[mips](var entry: Label) extends TacInstr.Visitor {
+
     private[mips] val seq = new mutable.ArrayBuffer[PseudoInstr]
     private[mips] var maxArgs = 0
     private var argCount = 0
@@ -216,8 +218,11 @@ final class MipsAsmEmitter extends AsmEmitter("mips", Mips.allocatableRegs, Mips
     }
 
     override def visitParm(instr: TacInstr.Parm): Unit = {
-      if (argCount < 4) seq += new Mips.Move(Mips.argRegs(argCount), instr.value)
-      else seq += new Mips.StoreWord(instr.value, Mips.SP, argCount * 4)
+      if (argCount < 4) {
+        seq += new Mips.Move(Mips.argRegs(argCount), instr.value)
+      } else {
+        seq += new Mips.StoreWord(instr.value, Mips.SP, argCount * 4)
+      }
       argCount += 1
     }
 

src/main/scala/decaf/backend/asm/mips/MipsSubroutineEmitter.scala

@@ -33,12 +33,14 @@ class MipsSubroutineEmitter private[mips](emitter: MipsAsmEmitter, info: Subrout
   extends SubroutineEmitter(emitter, info) {
 
   override def emitStoreToStack(src: Reg, temp: Temp): Unit = {
-    if (!offsets.contains(temp)) if (temp.index < info.numArgs) { // Always map arg `i` to `SP + 4 * i`.
-      offsets(temp) = 4 * temp.index
-    }
-    else {
-      offsets(temp) = nextLocalOffset
-      nextLocalOffset += 4
+    if (!offsets.contains(temp)) {
+      if (temp.index < info.numArgs) { // Always map arg `i` to `SP + 4 * i`.
+        offsets(temp) = 4 * temp.index
+      }
+      else {
+        offsets(temp) = nextLocalOffset
+        nextLocalOffset += 4
+      }
     }
     buf += new Mips.NativeStoreWord(src, Mips.SP, offsets(temp))
   }
@@ -77,7 +79,9 @@ class MipsSubroutineEmitter private[mips](emitter: MipsAsmEmitter, info: Subrout
     for {
       (reg, i) <- Mips.calleeSaved.zipWithIndex
       if used(reg)
-    } printer.printInstr(new Mips.NativeStoreWord(reg, Mips.SP, info.argsSize + 4 * i), "save value of " + reg)
+    } {
+      printer.printInstr(new Mips.NativeStoreWord(reg, Mips.SP, info.argsSize + 4 * i), "save value of " + reg)
+    }
     printer.printComment("end of prologue")
     printer.println()
 
@@ -94,8 +98,10 @@ class MipsSubroutineEmitter private[mips](emitter: MipsAsmEmitter, info: Subrout
     for {
       (reg, i) <- Mips.calleeSaved.zipWithIndex
       if used(reg)
-    } printer.printInstr(new Mips.NativeLoadWord(Mips.calleeSaved(i), Mips.SP, info.argsSize + 4 * i),
-      "restore value of $S" + i)
+    } {
+      printer.printInstr(new Mips.NativeLoadWord(Mips.calleeSaved(i), Mips.SP, info.argsSize + 4 * i),
+        "restore value of $S" + i)
+    }
     if (info.hasCalls) {
       printer.printInstr(new Mips.NativeLoadWord(Mips.RA, Mips.SP, info.argsSize + 32), "restore the return address")
     }

src/main/scala/decaf/backend/dataflow/BasicBlock.scala

@@ -12,6 +12,7 @@ import scala.collection.mutable
   * @tparam I type of the instructions stored in the block
   */
 trait BasicBlock[I <: PseudoInstr] extends Iterable[Loc[I]] {
+
   /**
     * Id, MUST be unique in one control flow graph.
     */
@@ -70,6 +71,7 @@ trait BasicBlock[I <: PseudoInstr] extends Iterable[Loc[I]] {
   */
 case class ContinuousBasicBlock[I <: PseudoInstr](id: Int, label: Option[Label], instrSeq: List[Loc[I]])
   extends BasicBlock[I] {
+
   override def iterator: Iterator[Loc[I]] = instrSeq.iterator
 
   override def seqIterator: Iterator[Loc[I]] = instrSeq.iterator
@@ -87,6 +89,7 @@ case class ContinuousBasicBlock[I <: PseudoInstr](id: Int, label: Option[Label],
   */
 case class EndByJumpBasicBlock[I <: PseudoInstr](id: Int, label: Option[Label], sequential: List[Loc[I]],
                                                  jump: Loc[I]) extends BasicBlock[I] {
+
   override def iterator: Iterator[Loc[I]] = (sequential :+ jump).iterator
 
   override def seqIterator: Iterator[Loc[I]] = sequential.iterator
@@ -107,6 +110,7 @@ case class EndByJumpBasicBlock[I <: PseudoInstr](id: Int, label: Option[Label],
   */
 case class EndByCondJumpBasicBlock[I <: PseudoInstr](id: Int, label: Option[Label], sequential: List[Loc[I]],
                                                      jump: Loc[I]) extends BasicBlock[I] {
+
   override def iterator: Iterator[Loc[I]] = (sequential :+ jump).iterator
 
   override def seqIterator: Iterator[Loc[I]] = sequential.iterator
@@ -126,6 +130,7 @@ case class EndByCondJumpBasicBlock[I <: PseudoInstr](id: Int, label: Option[Labe
   */
 case class EndByReturnBasicBlock[I <: PseudoInstr](id: Int, label: Option[Label], sequential: List[Loc[I]],
                                                    ret: Loc[I]) extends BasicBlock[I] {
+
   override def iterator: Iterator[Loc[I]] = (sequential :+ ret).iterator
 
   override def seqIterator: Iterator[Loc[I]] = sequential.iterator

src/main/scala/decaf/backend/dataflow/CFG.scala

@@ -20,7 +20,6 @@ import scala.collection.mutable
 class CFG[I <: PseudoInstr](nodes: List[BasicBlock[I]], edges: List[(Int, Int)])
   extends Iterable[BasicBlock[I]] {
 
-
   /**
     * Get basic block by id.
     *
@@ -92,6 +91,7 @@ class CFG[I <: PseudoInstr](nodes: List[BasicBlock[I]], edges: List[(Int, Int)])
 }
 
 object CFG {
+
   /**
     * Build a control flow graph from a sequence of instructions (in one function/subroutine).
     *
@@ -102,8 +102,9 @@ object CFG {
 
     @scala.annotation.tailrec
     def build(seq: List[I], label: Option[Label], bbs: List[BasicBlock[I]]): List[BasicBlock[I]] = {
-      if (seq.isEmpty) bbs
-      else {
+      if (seq.isEmpty) {
+        bbs
+      } else {
         val (sequential, remainder) = seq.span(_.isSequential)
         assert(remainder.nonEmpty)
         val end :: rest = remainder

src/main/scala/decaf/backend/dataflow/LivenessAnalyzer.scala

@@ -5,6 +5,7 @@ import decaf.lowlevel.instr.{PseudoInstr, Temp}
 import scala.collection.mutable
 
 class LivenessAnalyzer[I <: PseudoInstr] extends Function[CFG[I], Unit] {
+
   override def apply(graph: CFG[I]): Unit = {
     for (bb <- graph) {
       computeDefAndLiveUseFor(bb)
@@ -54,7 +55,9 @@ class LivenessAnalyzer[I <: PseudoInstr] extends Function[CFG[I], Unit] {
       loc.instr.getWritten.forEach(bb.`def`.add)
       loc.instr.getRead.forEach { t =>
         if (!bb.`def`.contains(t)) // used before being assigned to a value
+        {
           bb.liveUse.add(t)
+        }
       }
     }
   }