shithub: scc

ref: d6c6483728fa4ad0577f51fd26d7ef29ea91e7b3
dir: /flow.c/

#include <assert.h>
#include <stdint.h>
#include <stdio.h>

#include "cc.h"
#include "symbol.h"
#include "tokens.h"
#include "syntax.h"
#include "sizes.h"

static struct node *stmt(void);


static unsigned char blocks[NR_BLOCK];
static unsigned char *blockp = blocks;
struct symbol *curfun;

static void
push(register unsigned char b)
{
	if (blockp == &blocks[NR_BLOCK])
		error("Too much nesting levels");
	*blockp++ = b;
}

static void
pop(void)
{
	assert(blockp >= blocks);
	--blockp;
}

static struct node *
Goto(void)
{
	register struct node *np;
	register struct symbol *sym;


	expect(GOTO);
	expect(IDEN);
	sym = lookup(yytext, NS_LABEL);
	np = node(OGOTO, nodesym(sym), NULL);
	expect(';');

	return np;
}

static struct node *
While(void)
{
	register struct node *cond, *np;

	expect(WHILE);
	expect('(');
	cond = expr();
	expect(')');
	push(OWHILE);
	np = node(OWHILE, cond, stmt());
	pop();
	return np;
}

static struct node *
Do(void)
{
	register struct node *cond, *body, *np;

	expect(DO);
	body = stmt();
	expect(WHILE);
	expect('(');
	cond = expr();
	expect(')');
	expect(';');

	push(ODO);
	np = node(ODO, body, cond);
	pop();
	return np;
}

static struct node *
For(void)
{
	register struct node *exp1, *exp2, *exp3;
	struct node *np;

	expect(FOR);
	expect('(');
	exp1 = expr();
	expect(';');
	exp2 = expr();
	expect(';');
	exp3 = expr();
	expect(')');

	push(OFOR);
	np = node(OFOR, exp1,
	          node(O2EXP, exp2,
	               node(O2EXP, exp3, stmt())));
	pop();
	return np;
}

static struct node *
If(void)
{
	register struct node *cond, *body;

	expect(IF);
	expect('(');
	cond = expr();
	expect(')');
	body = stmt();

	return node(OIF, cond,
	            node(O2EXP, body, (accept(ELSE)) ? stmt() : NULL));
}

static struct node *
Switch(void)
{
	register struct node *cond, *np;

	expect(SWITCH);
	expect('(');
	cond = expr();
	expect(')');

	push(OSWITCH);
	np = node(OSWITCH, cond, stmt());
	pop();
	return np;
}

static struct node *
label(void)
{
	register struct symbol *sym = lookup(yytext, NS_LABEL);

	/* TODO: detect repeated labels */
	/* TODO: install in symbol table */
	next(), next();  	/* skip IDEN and ':' */
	return node(OLABEL, nodesym(sym), stmt());
}

static struct node *
Break(void)
{
	expect(BREAK);
	expect(';');
	if (blockp == blocks)
		error("break statement not within loop or switch");
	return node(OBREAK, NULL, NULL);
}

static struct node *
Continue(void)
{
	register unsigned char *bp;

	expect(CONTINUE);
	expect(';');

	for (bp = blocks; bp < blockp && *bp == OSWITCH; ++bp)
		; /* nothing */
	if (bp == blockp)
		error("continue statement not within loop");

	return node(OCONT, NULL, NULL);
}

static struct node *
Return(void)
{
	register struct node *np;

	expect(RETURN);
	np = expr();
	expect(';');

	return node(ORETURN, np, NULL);
}

static struct node *
Case(void)
{
	register unsigned char *bp;
	register struct node *np, *exp;

	expect(CASE);
	exp = expr();
	/* TODO: check if exp is constant */
	/* TODO: Check if the type is correct */
	for (bp = blocks; bp < blockp && *bp != OSWITCH; ++bp)
		; /* nothing */
	if (bp == blockp)
		error("case statement not within switch");
	np = node(OCASE, exp, NULL);
	expect(':');
	return np;
}

static struct node *
Default(void)
{
	register unsigned char *bp;

	expect(DEFAULT);
	for (bp = blocks; bp < blockp && *bp != OSWITCH; ++bp)
		; /* nothing */
	if (bp == blockp)
		error("default statement not within switch");
	expect(':');
	return node(ODEFAULT, NULL, NULL);
}

static struct node *
compound(void)
{
	expect('{');

repeat:	switch (yytoken) {
	case TYPE: case SCLASS: case TQUALIFIER:
		decl();
		goto repeat;
	case '}':
		next();
		return NULL;
	default:
		stmt();
		goto repeat;
	}
}

static struct node *
stmt(void)
{
	register struct node *np;

	switch (yytoken) {
	case '{':      return context(compound);
	case SWITCH:   return Switch();
	case IF:       return If();
	case FOR:      return For();
	case DO:       return Do();
	case WHILE:    return While();
	case CONTINUE: return Continue();
	case BREAK:    return Break();
	case RETURN:   return Return();
	case GOTO:     return Goto();
	case CASE:     return Case();
	case DEFAULT:  return Default();
	case IDEN:     if (ahead() == ':') return label();
	}
	np = expr();
	expect(';');
	return np;
}

struct node *
function(void)
{
	return node(OFTN, compound(), NULL);
}