cgen.h

<compiler construction principles and practice>书中定义的tiny语言编译器。

class Cgen:public Code,public SymTab
{
private:

	static int tmpOffset;
	

	void cGen (TreeNode * tree);
	void genStmt( TreeNode * tree);
	void genExp( TreeNode * tree);

public:
	Cgen(char *codefile):Code(codefile)
	{	 
	}

	void codeGen(TreeNode * syntaxTree, char * codefile);

};


int Cgen::tmpOffset = 0;


void Cgen:: genStmt( TreeNode * tree)
{ 
	TreeNode * p1, * p2, * p3;
    int savedLoc1,savedLoc2,currentLoc;
    int loc;
    switch (tree->kind.stmt) 
	{
	 case IfK :
         emitComment("-> if") ;
         p1 = tree->child[0] ;
         p2 = tree->child[1] ;
         p3 = tree->child[2] ;
        
         cGen(p1);
         savedLoc1 = emitSkip(1) ;
         emitComment("if: jump to else belongs here");
         
         cGen(p2);
         savedLoc2 = emitSkip(1) ;
         emitComment("if: jump to end belongs here");
         currentLoc = emitSkip(0) ;
         emitBackup(savedLoc1) ;
         emitRM_Abs("JEQ",ac,currentLoc,"if: jmp to else");
         emitRestore() ;
         
         cGen(p3);
         currentLoc = emitSkip(0) ;
         emitBackup(savedLoc2) ;
         emitRM_Abs("LDA",pc,currentLoc,"jmp to end") ;
         emitRestore() ;
         emitComment("<- if") ;
         break;

      case RepeatK:
         emitComment("-> repeat") ;
         p1 = tree->child[0] ;
         p2 = tree->child[1] ;
         savedLoc1 = emitSkip(0);
         emitComment("repeat: jump after body comes back here");
         
         cGen(p1);
        
         cGen(p2);
         emitRM_Abs("JEQ",ac,savedLoc1,"repeat: jmp back to body");
         emitComment("<- repeat") ;
         break;

      case AssignK:
         emitComment("-> assign") ;
         
         cGen(tree->child[0]);
         
         loc = Find(tree->attr.name);
         emitRM("ST",ac,loc,gp,"assign: store value");
         emitComment("<- assign") ;
         break;
      case ReadK:
         emitRO("IN",ac,0,0,"read integer value");
         loc = Find(tree->attr.name);
         emitRM("ST",ac,loc,gp,"read: store value");
         break;
      case WriteK:
         
         cGen(tree->child[0]);
         
         emitRO("OUT",ac,0,0,"write ac");
         break;
      default:
         break;
    }
} 

void Cgen:: genExp( TreeNode * tree)
{ 
	int loc;
    TreeNode * p1, * p2;
    switch (tree->kind.exp) 
	{

    case ConstK :
        emitComment("-> Const") ;
     
        emitRM("LDC",ac,tree->attr.val,0,"load const");
        emitComment("<- Const") ;
        break;
    
    case IdK :
        emitComment("-> Id") ;
        loc = Find(tree->attr.name);
        emitRM("LD",ac,loc,gp,"load id value");
        emitComment("<- Id") ;
        break;
    case OpK :
         emitComment("-> Op") ;
         p1 = tree->child[0];
         p2 = tree->child[1];
         
         cGen(p1);
        
         emitRM("ST",ac,tmpOffset--,mp,"op: push left");
         
         cGen(p2);
        
         emitRM("LD",ac1,++tmpOffset,mp,"op: load left");
         switch (tree->attr.op) {
            case PLUS :
               emitRO("ADD",ac,ac1,ac,"op +");
               break;
            case MINUS :
               emitRO("SUB",ac,ac1,ac,"op -");
               break;
            case TIMES :
               emitRO("MUL",ac,ac1,ac,"op *");
               break;
            case OVER :
               emitRO("DIV",ac,ac1,ac,"op /");
               break;
            case LT :
               emitRO("SUB",ac,ac1,ac,"op <") ;
               emitRM("JLT",ac,2,pc,"br if true") ;
               emitRM("LDC",ac,0,ac,"false case") ;
               emitRM("LDA",pc,1,pc,"unconditional jmp") ;
               emitRM("LDC",ac,1,ac,"true case") ;
               break;
            case EQ :
               emitRO("SUB",ac,ac1,ac,"op ==") ;
               emitRM("JEQ",ac,2,pc,"br if true");
               emitRM("LDC",ac,0,ac,"false case") ;
               emitRM("LDA",pc,1,pc,"unconditional jmp") ;
               emitRM("LDC",ac,1,ac,"true case") ;
               break;
            default:
               emitComment("BUG: Unknown operator");
               break;
         }
         emitComment("<- Op") ;
         break;

    default:
      break;
  }
} 


void Cgen::cGen( TreeNode * tree)
{ if (tree != NULL)
  { switch (tree->nodekind) {
      case StmtK:
        genStmt(tree);
        break;
      case ExpK:
        genExp(tree);
        break;
      default:
        break;
    }
    cGen(tree->sibling);
  }
}


void Cgen::codeGen(TreeNode * syntaxTree, char * codefile)
{
	char * s = new char[strlen(codefile)+7];
    strcpy(s,"File: ");
    strcat(s,codefile);
    emitComment("TINY Compilation to TM Code");
    emitComment(s);
  
    emitComment("Standard prelude:");
    emitRM("LD",mp,0,ac,"load maxaddress from location 0");
    emitRM("ST",ac,0,ac,"clear location 0");
    emitComment("End of standard prelude.");

    cGen(syntaxTree);
   
    emitComment("End of execution.");
    emitRO("HALT",0,0,0,"");
}