Month: December 2017

-> #put-type;#do-decl
-> int | float
-> #add-decl
-> #add-decl
-> ID#proc-decl
#put-type puts given type on semantic stack
#proc-decl builds decl record for var on stack
#add-decl builds decl-chain
p#do-decl traverses chain on semantic stack using backwards pointers entering each var into symbol table

float a, b, c

translation: generate temporary values, propagate them to keep semantic context

Compiler Structure
scanner -> parser -> semantic analysis -> intermdeiate representation -> code generation -> assembly code

Symbol Table

int a, b;
declares a and b, within current scope, type integer

Basic symbol table
name, type, scope
a, int, “main”

semantic action
1. enter variable declaration into symbol table
2. look up variables in symbol table
3. do binding of looked-up variables (scoping rules, etc.)
4. Do type checking for compatibility
5. keep the semantic context of processing
e.g. a + b + c -> t1 = a + b
t2 = t1 + c

Start
-parse
-get next token
-semantic analysis
-look up variable name
-do semantic checks -> generate code(passed) or semantic error(failed)
-put in symbol table

Front End: Analysis
1. Lexical Analysis
2. Syntax Analysis
3. Semantic Analysis

Back End: Systhesis
4. Code Generation
5. Optimization

Lexical rules of language dictate how legal word is formed by concatenating alphabet.

If x==1 then if y==2 print 1 else print 2
stmt -> if expr then stmt else stmt

High-level Language

C/Java Compiler

temp = v[k];
v[k] = v[k+1];
v[k+1] = temp;

Fortran Compiler

TEMP = V(K)
V(K) = V(K+1)
V(K+1) = TEMP

Assembly Language

lw $to, 0($2)
lw $t1, 4($2)
sw $t1, 0($2)
sw $to, 4($2)

#include

int main()
{
	char A = '2';
	int sum = A + 10;
	std::cout<<"sum ="<
		Author  blogPosted on 2017年12月24日2017年12月24日Categories Compiler