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CPM OPERATING SYSTEMS/CPM 68K/1.0X SOURCES/v101/c/parser/stmt.c

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+#
+/*
+	Copyright 1981
+	Alcyon Corporation
+	8474 Commerce Av.
+	San Diego, Ca.  92121
+*/
+
+#include "parser.h"
+#define	labgen(l,sl)	sl=l;l=nextlabel++;
+int swp -1;
+
+
+/* stmt - process a single statement*/
+stmt()									/* returns - none*/
+{
+	register int token, saveblab, saveclab, lab, i;
+	register struct tnode *tp;
+	register char *p;
+
+	while( 1 ) {
+		switch(token=gettok()) {
+
+		case LCURBR:					/*handle { ... }*/
+			while( next(EOF) == 0 ) {
+				if( next(RCURBR) )
+					return;
+				stmt();
+			}
+		case EOF:
+			error("{ not matched by }");
+		case SEMI:						/*null statement*/
+			return;
+
+		case RCURBR:
+			pbtok(token);
+			return;
+
+		case SYMBOL:					/*symbol: statement*/
+			if( peekc(':') ) {
+				dolabel();
+				continue;
+			}
+		default:						/*anything else...*/
+			pbtok(token);
+			outexpr(expr());
+			break;
+	
+		case RESWORD:
+			switch(cvalue) {
+	
+			case R_BREAK:
+				outgoto(brklabel());		/*branch to break label*/
+				break;
+	
+			case R_CASE:
+				docase();
+				continue;
+	
+			case R_CONTINUE:
+				outgoto(contlabel());		/*branch to continue label*/
+				break;
+	
+			case R_DEFAULT:
+				dodefault();
+				continue;
+	
+			case R_DO:
+				dodo();
+				break;
+	
+			case R_FOR:
+				dofor();
+				return;
+	
+			case R_GOTO:
+				outgoto(gotolabel());
+				break;
+	
+			case R_IF:
+				doif();
+				return;
+	
+			case R_RETURN:
+				doreturn();
+				break;
+	
+			case R_SWITCH:
+				doswitch();
+				return;
+	
+			case R_WHILE:
+				dowhile();
+				return;
+
+			default:
+				synerr("invalid keyword");
+				return;
+			}
+		}
+		if( next(SEMI) == 0 )
+			synerr("missing semicolon");
+		return;
+	}
+}
+
+/* balpar - handle expression within parenthesis for while and if*/
+/*		Merely checks for left and right parens and builds expression.*/
+char *balpar()							/* returns pointer to expression*/
+{
+	register struct tnode *tp;
+
+	if( next(LPAREN) ) {
+		tp = expr();
+		if( next(RPAREN) )
+			return(tp);
+	}
+	synerr("parenthesized expression syntax");
+	return(0);
+}
+
+/* synerr - syntax error*/
+/*		Outputs error message and tries to resyncronize input.*/
+synerr(s,x1,x2,x3,x4,x5,x6)				/* returns - none*/
+char *s;								/* printf format string*/
+int x1, x2, x3, x4, x5, x6;				/* printf arguments*/
+{
+	register int token;
+
+	error(s,x1,x2,x3,x4,x5,x6);
+	while( (token=gettok()) != SEMI && token != EOF && token != LCURBR &&
+			token != RCURBR )
+		;
+	pbtok(token);
+}
+
+/* gotolabel - gets label id for goto*/
+/*		This is used for both: goto symbol and if(...)goto symbol*/
+gotolabel()								/* returns 0 if not, else label id*/
+{
+	register struct symbol *sp;
+
+	if( next(SYMBOL) == 0 )
+		synerr("expected label");
+	else {
+		if( (sp=csp)->s_sc == 0 ) {
+			sp->s_type = LLABEL;
+			if( sp->s_offset == 0 )
+				sp->s_offset = nextlabel++;
+		}
+		if( (sp->s_sc == 0 || sp->s_sc == STATIC ) &&
+				sp->s_type == LLABEL )
+			return(sp->s_offset);
+		synerr("invalid label");
+	}
+	return(0);
+}
+
+/* dolabel - do statement label*/
+/*		Checks current symbol for already being defined, then sets*/
+/*		symbol attributes for label.*/
+dolabel()								/* returns - none*/
+{
+	register struct symbol *sp;
+
+	sp = csp;
+	if( sp->s_sc )
+		error("label redeclaration: %.8s",sp->s_symbol);
+	else {
+		sp->s_attrib =| SDEFINED;
+		sp->s_sc = STATIC;
+		sp->s_type = LLABEL;
+		if( sp->s_offset == 0 )
+			sp->s_offset = nextlabel++;
+		outlab(sp->s_offset);
+	}
+}
+
+/* brklabel - generate break label*/
+/*		Checks if break label is undefined, and if so, generates message*/
+brklabel()								/* returns label number*/
+{
+	if( blabel == 0 )
+		error("invalid break statement");
+	return(blabel);
+}
+
+/* contlabel - generate continue label*/
+/*		Checks if continue label is undefined, and if so, generates message*/
+contlabel()								/* returns label number*/
+{
+	if( clabel == 0 )
+		error("invalid continue statement");
+	return(clabel);
+}
+
+/* docase - handles: case constant : statement*/
+/*		Checks for being in a switch statement, adds entry to switch table*/
+docase()								/* returns - none*/
+{
+	register int value, lab;
+
+	colonstop++;
+	value = cexpr();					/*get case value*/
+	colonstop--;
+	if( next(COLON) == 0 )				/*check for colon*/
+		synerr("missing colon");
+	if( swp < 0 )
+		error("case not inside a switch block");
+	else if( swp >= (SWSIZE-1) )
+		error("too many cases in switch");
+	else {
+		addswitch(&swtab[cswp],swp-cswp,value,lab=nextlabel++);
+		outlab(lab);
+		swp++;
+	}
+}
+
+/* dodefault - handles: default : statement*/
+/*		Checks for colon and being in a switch statement*/
+dodefault()								/* returns - none*/
+{
+	if( next(COLON) == 0 )
+		error("missing colon");
+	if( swp < 0 )
+		error("default not inside a switch block");
+	else {
+		dlabel = nextlabel++;			/*allocate default label*/
+		outlab(dlabel);					/*output default label*/
+	}
+}
+
+/* dodo - handles: do statement while ( expression )*/
+dodo()									/* returns - none*/
+{
+	register int lab, saveblab, saveclab;
+
+	labgen(blabel,saveblab);
+	labgen(clabel,saveclab);
+	lab = nextlabel++;
+	outlab(lab);						/*branch back to here*/
+	stmt();								/*do statement*/
+	outlab(clabel);						/*continue label*/
+	if( nextrw(R_WHILE) == 0 ) {
+		error("missing while");			/*only advisory...*/
+		outgoto(lab);
+	}
+	else
+		outifgoto(balpar(),TRUE,lab);		/*while expression*/
+	outlab(blabel);						/*break label*/
+	blabel = saveblab;					/*restore labels*/
+	clabel = saveclab;
+}
+
+/* dofor - handle: for ( expression ; expression ; expression ) statement*/
+/*		Hard part is handling re-initialization expression, which is*/
+/*		parsed and saved, then the statement is parsed, then the reinit*/
+/*		clause expression tree is output.*/
+dofor()									/* returns - none*/
+{
+	register int lab, saveblab, saveclab, reinit, clineno;
+	register char *savep;
+	register struct tnode *tp;
+
+	labgen(blabel,saveblab);
+	labgen(clabel,saveclab);
+	if( next(LPAREN) == 0 ) {
+forerr:
+		synerr("invalid for statement");
+		return;
+	}
+	if( next(SEMI) == 0 ) {				/*do init expression*/
+		outexpr(expr());
+		if( next(SEMI) == 0 )
+			goto forerr;
+	}
+	outlab(clabel);						/*branch back to here*/
+	if( next(SEMI) == 0 ) {				/*do for condition*/
+		outifgoto(expr(),FALSE,blabel);
+		if( next(SEMI) == 0 )
+			goto forerr;
+	}
+	if( next(RPAREN) ) {				/*no re-init - easy case*/
+		stmt();							/*output statement*/
+		outgoto(clabel);					/*output continue label*/
+	}
+	else {								/*there is a re-init clause*/
+		labgen(clabel,lab);
+		savep = exprp;
+		tp = expr();					/*save re-init tree until done*/
+		exprp = opap;					/*remember until reinit is output*/
+		reinit = lineno;
+		if( next(RPAREN) == 0 )
+			goto forerr;
+		stmt();							/*do statment*/
+		clineno = lineno;
+		lineno = reinit;
+		outlab(clabel);					/*we branch to here for reinit*/
+		outexpr(tp);					/*output re-init clause*/
+		exprp = savep;
+		lineno = clineno;
+		outgoto(lab);						/*branch back to top of loop*/
+	}
+	outlab(blabel);						/*break to here*/
+	blabel = saveblab;
+	clabel = saveclab;					/*restore labels*/
+}
+
+/* doif - handles: if ( expression ) statement [ else statement ]*/
+/*		Handles special cases for goto, break, continue and return.*/
+doif()									/* returns - none*/
+{
+	register struct tnode *tp;
+	register int elselab, exitlab;
+
+	tp = balpar();						/*if( expr )...*/
+	exitlab = 0;
+	if( nextrw(R_GOTO) )
+		exitlab = gotolabel();
+	else if( nextrw(R_BREAK) )
+		exitlab = brklabel();
+	else if( nextrw(R_CONTINUE) )
+		exitlab = contlabel();
+	else if( nextrw(R_RETURN) ) {
+		if( peekc(';') ) {
+			exitlab = rlabel;
+			putback(';');
+		}
+		else
+			pbtok(RESWORD);
+	}
+	if( exitlab ) {						/*easy goto, do branch if true*/
+		outifgoto(tp,TRUE,exitlab);
+		if( next(SEMI) == 0 )
+			synerr("missing semicolon");
+		if( nextrw(R_ELSE) )				/*else clause, just output it*/
+			stmt();
+	}
+	else {								/*hard goto, branch over statement*/
+		elselab = nextlabel++;
+		outifgoto(tp,FALSE,elselab);
+		stmt();
+		if( nextrw(R_ELSE) ) {
+			exitlab = nextlabel++;		/*branches over else clause*/
+			outgoto(exitlab);				/*branch out of then clause*/
+			outlab(elselab);			/*label to start else clause*/
+			stmt();						/*else statement*/
+			outlab(exitlab);
+		}
+		else
+			outlab(elselab);			/*no else, just branch out*/
+	}
+}
+
+/* doreturn - handles: return [ expression ] ;*/
+/*		Expression is the hard part, must create an assignment expression*/
+/*		to assign expression to the type of the function, then get it*/
+/*		loaded into a specific register.*/
+doreturn()								/* returns - none*/
+{
+	register int savelreg;
+	register struct tnode *tp;
+
+	if( peekc(';') == 0 ) {				/*need to compute return?*/
+		opp = opstack;
+		opdp = opdstack;
+		pushopd(frp);					/*push function return info node*/
+		pushopd(expr());				/*get return expression*/
+		savelreg = loadreg;
+		loadreg = 1;
+		maketree(ASSIGN);				/*do assignment for conversion*/
+		loadreg = savelreg;
+		outforreg(popopd()->t_right);
+		opp = 0;
+		opdp = 0;
+	}
+	else
+		putback(';');
+	outgoto(rlabel);						/*branch to the return label*/
+}
+
+/* doswitch - handles: switch ( expression ) statement*/
+/*		Evaluates the expression, forces the result into a known register*/
+/*		collects the case statements in swtab, then outputs the switch*/
+/*		operator and switch cases.*/
+doswitch()								/* returns - none*/
+{
+	register int saveblab, swlab, savedlab, saveswp, i;
+	register struct tnode *tp;
+
+	labgen(blabel,saveblab);
+	tp = balpar();
+	integral(tp,-1);					/*must be integral type result*/
+	outforreg(tp);						/*compile to reg 0*/
+	saveswp = swp;						/*remember old switch pointer*/
+	if( saveswp < 0 )
+		swp++;
+	i = cswp;
+	cswp = swp;							/*remember real first entry*/
+	swlab = nextlabel++;
+	outgoto(swlab);						/*branch to switch code*/
+	savedlab = dlabel;
+	dlabel = 0;
+	stmt();								/*do switch statement*/
+	outgoto(blabel);						/*output branch just in case*/
+	outlab(swlab);						/*here we now do the switch code*/
+	if( dlabel == 0 )
+		dlabel = blabel;
+	outswitch(swp-cswp,dlabel,&swtab[cswp]);
+	outlab(blabel);						/*break to here*/
+	cswp = i;
+	swp = saveswp;
+	blabel = saveblab;
+	dlabel = savedlab;
+}
+
+/* dowhile - handles: while ( expression ) statement*/
+/*		This is fairly straight-forward.*/
+dowhile()								/* returns - none*/
+{
+	register int saveclab, saveblab;
+
+	labgen(blabel,saveblab);
+	labgen(clabel,saveclab);
+	outlab(clabel);						/*continue label*/
+	outifgoto(balpar(),FALSE,blabel);		/*condition clause*/
+	stmt();								/*statement*/
+	outgoto(clabel);						/*branch back to top of loop*/
+	outlab(blabel);						/*break to here*/
+	blabel = saveblab;
+	clabel = saveclab;					/*restore labels*/
+}
+
+/* nextrw - is next token the specified reserved word?*/
+nextrw(rw)								/* returns 1 if match, 0 otherwise*/
+int rw;									/* reserved word to match*/
+{
+	register int token;
+
+	if( (token=gettok()) != RESWORD || cvalue != rw ) {
+		pbtok(token);
+		return(0);
+	}
+	return(1);
+}
+
+/* addswitch - add an entry into current switch table, bubble sorting*/
+/*		This makes it easier on the code generator and also checks for*/
+/*		duplicate labels at the "right" time.*/
+addswitch(sp,ncases,nval,nlab)		/* returns - none*/
+struct swtch *sp;						/* switch table pointer*/
+int ncases;								/* number of cases in switch*/
+int nval;								/* new value*/
+int nlab;								/* new label*/
+{
+	register struct swtch *nswp, *s;
+	register int temp, i;
+
+	nswp = &sp[ncases];
+	nswp->sw_value = nval;
+	nswp->sw_label = nlab;
+	s = nswp--;
+	for( ; --ncases >= 0; s--, nswp-- ) {
+		if( s->sw_value == nswp->sw_value )
+			error("duplicate case value");
+		if( s->sw_value < nswp->sw_value ) {
+			temp = s->sw_value;
+			s->sw_value = nswp->sw_value;
+			nswp->sw_value = temp;
+			temp = s->sw_label;
+			s->sw_label = nswp->sw_label;
+			nswp->sw_label = temp;
+		}
+	}
+}