shithub: scc

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Add while statements

These statements are transformed into do-while statements because
you save a jump in every iteration.

--- a/cc1.h

+++ b/cc1.h

@@ -228,7 +228,8 @@

 	emitdcl(Symbol *), emitsframe(Symbol *), emiteframe(Symbol *),

 	emitsym(Node *), emitunary(Node *),

 	emitbin(Node *), emitexp(Node *),

-	emitprint(Node *);

+	emitprint(Node *), emitlabel(Symbol *), emitjump(Symbol *, Node *),

+	emitbloop(void), emiteloop(void);

 extern Node

 	*node(void (*code)(Node *),

--- a/code.c

+++ b/code.c

@@ -206,6 +206,34 @@

 	emittype(tp);

 }

+void

+emitlabel(Symbol *sym)

+{

+	printf("L%d\n", sym->id);

+}

+

+void

+emitbloop(void)

+{

+	puts("\td");

+}

+

+void

+emiteloop(void)

+{

+	puts("\tb");

+}

+

+void

+emitjump(Symbol *sym, Node *np)

+{

+	printf("\tj\tL%d", sym->id);

+	if (!np)

+		putchar('\n');

+	else

+		emitexp(np);

+}

+

 Node *

 castcode(Node *child, Type *tp)

 {

--- a/expr.c

+++ b/expr.c

@@ -307,7 +307,7 @@

 	error(err);

 }

-static Node *

+Node *

 iszero(Node *np)

 {

 	if (ISNODECMP(np))

--- a/stmt.c

+++ b/stmt.c

@@ -8,8 +8,20 @@

 Symbol *curfun;

 extern Node *convert(Node *np, Type *tp1, char iscast);

+extern Node * iszero(Node *np);

 static void stmt(Symbol *lbreak, Symbol *lcont, Symbol *lswitch);

+static Symbol *

+label(char *s)

+{

+	if (!s)

+		s = "";

+	else if (lookup(s, NS_LABEL))

+		error("label '%s' already defined", s);

+

+	return install(s, NS_LABEL);

+}

+

 static Node *

 stmtexp(void)

 {

@@ -18,7 +30,35 @@

 	return np;

 }

+static Node *

+condition(void)

+{

+	Node *np;

+

+	expect('(');

+	np = iszero(expr());

+	expect(')');

+	return np;

+}

+

 static void

+While(Symbol *lswitch)

+{

+	Symbol *begin= label(NULL), *cond = label(NULL), *end = label(NULL);

+	Node *np;

+

+	expect(WHILE);

+	np = condition();

+	emitjump(cond, NULL);

+	emitbloop();

+	emitlabel(begin);

+	stmt(begin, end, lswitch);

+	emitlabel(cond);

+	emitjump(begin, np);

+	emiteloop();

+}

+

+static void

 Return(void)

 {

 	Node *np;

@@ -63,6 +103,8 @@

 	switch (yytoken) {

 	case '{': compound(lbreak, lcont, lswitch); break;

 	case RETURN: Return(); break;

+	case WHILE: While(lswitch); break;

 	default: emitexp(stmtexp()); break;

 	}

-}

\ No newline at end of file

+}

+