CS453 Intro and PA1 1CS453 Lecture PA7 overview 1Plan for today PA7 overview Expression Tree intermediate representation Possible approaches for performing translation– All visitor methods return a Translate.Exp reference– Visitor methods return void, but map AST nodes to Tree.Exp nodes and alist of Tree.StmCS453 Lecture PA7 overview 2PA7 Overview TranslateToIRTree.java– driver for PA7 ast_visitors/– BuildSymTable.java has one new piece– Translate.java– Frag.java Tree/* Temp/– TempMap.java interface Frame/– new functionality added to Frame.java interface and Access.java interface Mips/– MipsFrame.java implements the new functionality– InFrame.java implements the Tree.Exp exp(Tree.Exp) method SymTable/– VarSTE, LocalSTE, and MemberSTE implement Tree.Exp exp(Tree.Exp)– ClassSTE has getNumMembers() methodCS453 Lecture PA7 overview 3TempMap functionality in MipsFrame static final Temp ZERO = new Temp(); // zero reg static final Temp V0 = new Temp(); // function result static final Temp T0 = new Temp(); // caller-saved static final Temp T1 = new Temp(); ... static final Temp SP = new Temp(); // stack pointer static final Temp S8 = new Temp(); // callee-save (frame pointer) static final Temp RA = new Temp(); // return address private static final HashMap<Temp,String> tempMap = new HashMap<Temp,String>(32); static { tempMap.put(ZERO, "$0"); tempMap.put(V0, "$v0"); tempMap.put(T0, "$t0"); ... tempMap.put(SP, "$sp"); tempMap.put(S8, "$fp"); tempMap.put(RA, "$ra"); } public String tempMap(Temp temp) { if (tempMap.containsKey(temp)) { return tempMap.get(temp); } else { return temp.toString(); } }CS453 Lecture PA7 overview 4TranslateToIRTree driver // translate the AST to the IR Tree data structure Translate translateVisitor = new Translate(globalST, frame); ast.apply(translateVisitor); ... // debug output translateVisitor.outputTrees(new PrintWriter(IRTdot_out)); // result output Iterator<Frag> fragIter = translateVisitor.getResults(); ... Tree.Print pv = new Tree.Print(printWriter,frame); while (fragIter.hasNext()) { Frag frag = fragIter.next(); printWriter.println("===================================="); printWriter.println(frag.frame.name.toString()); pv.prStmList(frag.body); printWriter.println(); }CS453 Intro and PA1 2CS453 Lecture PA7 overview 5Key features in Translate HashMaps Frag list outputTrees– use for debuggingprivate LinkedList<Frag> frags = new LinkedList<Frag>();public Iterator<Frag> getResults() { return frags.iterator();}// mapping of nodes in AST to Tree.Exp'sprivate Map<Node,Tree.Exp> mNodeToTreeExp;// mapping of AST nodes to a list of Tree.Stmprivate Map<Node,List<Tree.Stm>> mNodeToTreeStmList;CS453 Lecture PA7 overview 6Tree intermediate representation ExpCONST(int i) - The integer constant i ExpNAME(Label n) - Constant address. Corresponds to label in assembly. ExpTEMP(Temp t) - Temporary t. “Infinite” Temps in Tree IR. ExpBINOP(int binop, Exp left, Exp right) - left binop right ExpMEM(Exp exp) - If left child of move, then store into address calculated by exp.Otherwise, fetch value at address calculated by exp. ExpCALL(Exp func, List<Exp> args) - evaluate func to find func address, thenevaluate args left to right. StmMOVE(Temp t, e) - Eval e and put result in t. StmMOVE(ExpMEM(e1), e2) - Eval e2 and store into address e1. StmEXP(Exp e) - Eval e and ignore result StmJUMP(Label targ) - Transfer control to given label. StmCJUMP(int rel, Exp l, Exp r, Label t, Label f) - if l rel r then goto t else goto f StmLABEL(Label l) - Label in
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