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CS 453: Compiler Construction Review Structure of the MiniJava Compiler Analysis Synthesis Phases of the compiler lexicographical analysis, or scanning (regular expressions) character stream syntactic analysis, or parsing (context

  1. CS 453: Compiler Construction Review Structure of the MiniJava Compiler Analysis Synthesis Phases of the compiler – lexicographical analysis, or scanning (regular expressions) character stream – syntactic analysis, or parsing (context free grammars) PA3 lexical analysis IR code generation PA6 – building the abstract syntax tree (syntax-directed translation) – building the symbol table (visitor design pattern) tokens “words” Assem (MIPS) – semantic analysis, or type checking (visitor design pattern) PA4 syntactic analysis – code generation (visitor design pattern) 553 optimization – 3-address code AST “sentences” Assem (MIPS) – Assem(MIPS) PA5 semantic analysis How would adding floats to the MiniJava compiler affect each phase? code gen AST and symbol table MIPS CS453 Lecture Final Review 1 CS453 Lecture Final Review 2 Specifying Tokens with JFlex Interaction Between Scanning and Parsing JFlex example input file: LETTER=[A-Za-z] DIGIT=[0-9] package mjparser; import java_cup.runtime.Symbol; UNDERSCORE="_" LETT_DIG_UND={LETTER}|{DIGIT}|{UNDERSCORE} lexer.next_token() ID={LETTER}({LETT_DIG_UND})* parse tree %% %line or AST character stream %char %% Lexical %cup "&&" { return new Symbol(sym.AND, new Parser %public TokenValue(yytext(), yyline, yychar)); } analyzer %eofval{ token return new Symbol(sym.EOF, new "boolean" {return new TokenValue("EOF", yyline, yychar)); Symbol(sym.BOOLEAN,... %eofval} {ID} { return new Symbol(sym.ID, new ... CS453 Lecture Final Review 3 CS453 Lecture Final Review 4 1

  2. Specifying Grammar with JavaCUP Abstract Syntax Tree for Memory Layout Example JavaCUP example input file: start with program; package mjparser; import java_cup.runtime.*; program ::= import ast.node.*; main_class:m class_decl_list:l ... {: RESULT = new Program(m,l); :} terminal AND, ASSIGN, INT; ; terminal mjparser.TokenValue NUMBER; ... exp ::= non terminal Program program; | NUMBER:n non terminal List<IClassDecl> {: Token token = new Token(n.text, class_decl_list; n.line, n.pos); RESULT = new IntegerExp( token ); non terminal MainClass :} main_class; ... CS453 Lecture Final Review 5 CS453 Lecture Final Review 6 Semantic Analysis Compiler Data Structures Determine whether source is meaningful Symbol Tables – Compile-time data structure – Check for semantic errors – Holds names, type information, and scope information for variables – Check for type errors Scopes – Gather type information for subsequent stages – A name space – Relate variable uses to their declarations e.g., In Pascal, each procedure creates a new scope e.g., In C, each set of curly braces defines a new scope – Can create a separate symbol table for each scope Example errors (from C) – What are the scopes in MiniJava? function1 = 3.14159; Using Symbol Tables x = 570 + “hello, world!” – For each variable declaration: scalar[i] – Check for symbol table entry – Add new entry; add type info – For each variable use: – Check symbol table entry CS453 Lecture Final Review 7 CS453 Lecture Final Review 8 2

  3. Example Symbol Table Compiling Procedures Properties of procedures higher addresses – Procedures/methods/functions define scopes AR: zoo – Procedure lifetimes are nested – Can store information related to dynamic invocation of a procedure on a call stack ( activation record or AR or AR: goo stack frame): – Space for saving registers – Space for passing parameters and returning values class And { AR: foo public static void main(String[] a){ – Space for local variables System.out.println(new Foo().testing(42)); }} – Return address of calling instruction class Foo { AR: foo public int testing(int p) { Stack management int x; – Push an AR on procedure entry (caller or callee) if (p < 10 && 2 < p) { lower addresses stack x = 7; – Pop an AR on procedure exit (caller or callee) } else { – Why do we need a stack? x = 22; } return x;}} CS453 Lecture Final Review 9 CS453 Lecture Final Review 10 Stack Frame for MiniJava Compiler Assem intermediate representation int foo(int x,int y,int *z) { .text Assem.Instr int a; .globl main main: – “assembly language instruction without register assignments” a = x * y - *z; sw $ra, 0($sp) #PUSH return a; subu $sp, $sp, 4 } sw $fp, 0($sp) #PUSH OPER(String assem, List<Temp> dst, List<Temp> src, List<Label> jumps) void main() { subu $sp, $sp, 4 – contains a string with holes for registers indicated by `d# and `s# and holes for labels addu $fp, $sp, 8 int x; indicated by `j# subu $sp, $fp, 12 x = 2; li $t0, 2 – dst and src are lists of Temps whose register assignment should fill holes cout << foo(4,5,&x); sw $t0, -8($fp) cout << "\n"; – first entry in src is associated with `s0, second with `s1, etc. li $t0, 4 } sw $t0, 0($sp) #PUSH – first entry in dst is associated with `d0, etc. subu $sp, $sp, 4 – jumps is a list of labels for filling in label holes .text li $t0, 5 _foo: sw $t0, 0($sp) #PUSH sw $ra, 0($sp) #PUSH subu $sp, $sp, 4 subu $sp, $sp, 4 subu $t0, $fp, 8 sw $fp, 0($sp) #PUSH sw $t0, 0($sp) #PUSH subu $sp, $sp, 4 subu $sp, $sp, 4 addu $fp, $sp, 20 jal _foo subu $sp, $fp, 24 move $a0, $v0 ... ... lw $t0, -20($fp) lw $ra, 0($fp) move $v0, $t0 move $t0, $fp lw $ra, -12($fp) lw $fp, -4($fp) move $t0, $fp move $sp, $t0 lw $fp, -16($fp) jr $ra move $sp, $t0 jr $ra CS453 Lecture Final Review 11 CS453 Lecture Final Review 12 3

  4. Assem intermediate representation cont ... Instruction selection for x86-64 Registers LABEL(String assem, Label label) – 16 64-bit registers RSP, the stack pointer register – a label statement in the target code – RSP, the stack pointer register • RBP, the frame pointer register – RBP, the frame pointer register MOVE(String assem, Temp dst, Temp src) – 32-bit register names used to access lower 32-bits of corresponding 64-bit register: – similar to OPER in that assem string contains holes, but .. eax, edx, exc, ebx, esi, esi, edi, esp and ebp – no jumps Representations – only one src and dst Temp – Constants prefixed with ‘$’, for example $3, $4, $-5, etc – Registers prefixed with ‘%’, for example %rsp, %rbp, etc. CJUMP(String a, Temp.Temp src1, RELOP op, Temp.Temp src2, Some Instructions Temp.Label t, Temp.Label f) – movl %eax, -12(%rbp) // M[%rbp-12] = %eax – similar to OPER in that assem string contains holes, but .. – addl -20(%rbp), %eax // %eax = M[%rbp-20] * %eax – only jumps to true and false target – only two source Temps for comparison – cmpl -4(%rbp), %eax – explicit conditional operation, which enables later changes in code layout – jge .L2 // if ( M[%rbp-4] >= %eax ) goto .L2 CS453 Lecture Final Review 13 CS453 Lecture Final Review 14 x86-64 example Example continued... .file "funcCall2.c” .globl main .text .type main, @function .globl foo main: .type foo, @function pushq %rbp # %rsp = %rsp-8; M[%esp ] = %rbp; foo: pushes onto stack pushq %rbp # %rsp = %rsp-8; M[%esp ] = %rbp movq %rsp, %rbp # %rbp = %rsp movq %rsp, %rbp # %rbp = %rsp subq $16, %rsp # %rsp = %rsp - 16 movl %edi, -20(%rbp) # storing parameters to stack movl $5, %esi # %esi = 5 movl %esi, -24(%rbp) movl $4, %edi # %edi = 4 movl -24(%rbp), %eax # accessing x addl -20(%rbp), %eax # adding y to x and storing in %eax call foo movl %eax, -4(%rbp) movl %eax, -4(%rbp) # M[%rbp-4] = %eax movl -4(%rbp), %eax movl -4(%rbp), %eax # %eax = M[%rbp-4] leave leave ret ret .size foo, .-foo CS453 Lecture Final Review 15 CS453 Lecture Final Review 16 4

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