6 files changed, 143 insertions, 0 deletions
diff --git a/src/cmd/5g/gsubr.c b/src/cmd/5g/gsubr.c
index 83a9949d6..57cb56a64 100644
--- a/src/cmd/5g/gsubr.c
+++ b/src/cmd/5g/gsubr.c
@@ -125,6 +125,64 @@ newplist(void)
 }
 
 void
+clearstk(void)
+{
+	Plist *pl;
+	Prog *p, *p1, *p2, *p3;
+	Node dst, end, zero, con;
+
+	if(plast->firstpc->to.offset <= 0)
+		return;
+
+	// reestablish context for inserting code
+	// at beginning of function.
+	pl = plast;
+	p1 = pl->firstpc;
+	p2 = p1->link;
+	pc = mal(sizeof(*pc));
+	clearp(pc);
+	p1->link = pc;
+	
+	// zero stack frame
+
+	// MOVW $4(SP), R1
+	nodreg(&dst, types[tptr], 1);
+	p = gins(AMOVW, N, &dst);
+	p->from.type = D_CONST;
+	p->from.reg = REGSP;
+	p->from.offset = 4;
+
+	// MOVW $n(R1), R2
+	nodreg(&end, types[tptr], 2);
+	p = gins(AMOVW, N, &end);
+	p->from.type = D_CONST;
+	p->from.reg = 1;
+	p->from.offset = p1->to.offset;
+	
+	// MOVW $0, R3
+	nodreg(&zero, types[TUINT32], 3);
+	nodconst(&con, types[TUINT32], 0);
+	gmove(&con, &zero);
+
+	// L:
+	//	MOVW.P R3, 0(R1) +4
+	//	CMP R1, R2
+	//	BNE L
+	p = gins(AMOVW, &zero, &dst);
+	p->to.type = D_OREG;
+	p->to.offset = 4;
+	p->scond |= C_PBIT;
+	p3 = p;
+	p = gins(ACMP, &dst, N);
+	raddr(&end, p);
+	patch(gbranch(ABNE, T), p3);
+
+	// continue with original code.
+	gins(ANOP, N, N)->link = p2;
+	pc = P;
+}	
+
+void
 gused(Node *n)
 {
 	gins(ANOP, n, N);	// used
diff --git a/src/cmd/6g/gsubr.c b/src/cmd/6g/gsubr.c
index c3dac1fdc..78b8c4351 100644
--- a/src/cmd/6g/gsubr.c
+++ b/src/cmd/6g/gsubr.c
@@ -121,6 +121,44 @@ newplist(void)
 }
 
 void
+clearstk(void)
+{
+	Plist *pl;
+	Prog *p1, *p2;
+	Node sp, di, cx, con, ax;
+
+	if((uint32)plast->firstpc->to.offset <= 0)
+		return;
+
+	// reestablish context for inserting code
+	// at beginning of function.
+	pl = plast;
+	p1 = pl->firstpc;
+	p2 = p1->link;
+	pc = mal(sizeof(*pc));
+	clearp(pc);
+	p1->link = pc;
+	
+	// zero stack frame
+	nodreg(&sp, types[tptr], D_SP);
+	nodreg(&di, types[tptr], D_DI);
+	nodreg(&cx, types[TUINT64], D_CX);
+	nodconst(&con, types[TUINT64], (uint32)p1->to.offset / widthptr);
+	gins(ACLD, N, N);
+	gins(AMOVQ, &sp, &di);
+	gins(AMOVQ, &con, &cx);
+	nodconst(&con, types[TUINT64], 0);
+	nodreg(&ax, types[TUINT64], D_AX);
+	gins(AMOVQ, &con, &ax);
+	gins(AREP, N, N);
+	gins(ASTOSQ, N, N);
+
+	// continue with original code.
+	gins(ANOP, N, N)->link = p2;
+	pc = P;
+}	
+
+void
 gused(Node *n)
 {
 	gins(ANOP, n, N);	// used
diff --git a/src/cmd/8g/gsubr.c b/src/cmd/8g/gsubr.c
index 8ed7e5564..ae9901eeb 100644
--- a/src/cmd/8g/gsubr.c
+++ b/src/cmd/8g/gsubr.c
@@ -123,6 +123,44 @@ newplist(void)
 }
 
 void
+clearstk(void)
+{
+	Plist *pl;
+	Prog *p1, *p2;
+	Node sp, di, cx, con, ax;
+
+	if(plast->firstpc->to.offset <= 0)
+		return;
+
+	// reestablish context for inserting code
+	// at beginning of function.
+	pl = plast;
+	p1 = pl->firstpc;
+	p2 = p1->link;
+	pc = mal(sizeof(*pc));
+	clearp(pc);
+	p1->link = pc;
+	
+	// zero stack frame
+	nodreg(&sp, types[tptr], D_SP);
+	nodreg(&di, types[tptr], D_DI);
+	nodreg(&cx, types[TUINT32], D_CX);
+	nodconst(&con, types[TUINT32], p1->to.offset / widthptr);
+	gins(ACLD, N, N);
+	gins(AMOVL, &sp, &di);
+	gins(AMOVL, &con, &cx);
+	nodconst(&con, types[TUINT32], 0);
+	nodreg(&ax, types[TUINT32], D_AX);
+	gins(AMOVL, &con, &ax);
+	gins(AREP, N, N);
+	gins(ASTOSL, N, N);
+
+	// continue with original code.
+	gins(ANOP, N, N)->link = p2;
+	pc = P;
+}	
+
+void
 gused(Node *n)
 {
 	gins(ANOP, n, N);	// used
diff --git a/src/cmd/gc/dcl.c b/src/cmd/gc/dcl.c
index 99af18d9f..8e790ef08 100644
--- a/src/cmd/gc/dcl.c
+++ b/src/cmd/gc/dcl.c
@@ -1233,9 +1233,14 @@ funccompile(Node *n, int isclosure)
 	stksize = 0;
 	dclcontext = PAUTO;
 	funcdepth = n->funcdepth + 1;
+	hasgoto = 0;
 	compile(n);
+	if(hasgoto)
+		clearstk();
 	curfn = nil;
 	funcdepth = 0;
 	dclcontext = PEXTERN;
 }
 
+
+
diff --git a/src/cmd/gc/gen.c b/src/cmd/gc/gen.c
index 8ad6c437d..857fcbef9 100644
--- a/src/cmd/gc/gen.c
+++ b/src/cmd/gc/gen.c
@@ -205,6 +205,7 @@ gen(Node *n)
 		break;
 
 	case OGOTO:
+		hasgoto = 1;
 		newlab(OGOTO, n, N);
 		gjmp(P);
 		break;
diff --git a/src/cmd/gc/go.h b/src/cmd/gc/go.h
index f58b76789..4b4e8fcd1 100644
--- a/src/cmd/gc/go.h
+++ b/src/cmd/gc/go.h
@@ -1246,3 +1246,6 @@ void	zhist(Biobuf *b, int line, vlong offset);
 void	zname(Biobuf *b, Sym *s, int t);
 void	data(void);
 void	text(void);
+
+EXTERN	int	hasgoto;
+void	clearstk(void);