cmd/5g, cmd/6g, cmd/8g: delete clearstk

Dreg from https://golang.org/cl/4629042

R=ken2
CC=golang-dev
https://golang.org/cl/6259057

src/cmd/5g/gsubr.c

@@ -174,64 +174,6 @@ newplist(void)
 	return pl;
 }
 
-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, 0), p3);
-
-	// continue with original code.
-	gins(ANOP, N, N)->link = p2;
-	pc = P;
-}	
-
 void
 gused(Node *n)
 {

src/cmd/6g/gsubr.c

@@ -172,44 +172,6 @@ newplist(void)
 	return pl;
 }
 
-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)
 {

src/cmd/8g/gsubr.c

@@ -173,44 +173,6 @@ newplist(void)
 	return pl;
 }
 
-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)
 {