Imported Upstream version 2011.06.23upstream-weekly/2011.06.23

1 files changed, 71 insertions, 0 deletions

diff --git a/src/cmd/5g/gsubr.c b/src/cmd/5g/gsubr.c
index bc39912ea..2d9218461 100644
--- a/src/cmd/5g/gsubr.c
+++ b/src/cmd/5g/gsubr.c
@@ -102,6 +102,19 @@ patch(Prog *p, Prog *to)
 	p->to.offset = to->loc;
 }
 
+Prog*
+unpatch(Prog *p)
+{
+	Prog *q;
+
+	if(p->to.type != D_BRANCH)
+		fatal("unpatch: not a branch");
+	q = p->to.branch;
+	p->to.branch = P;
+	p->to.offset = 0;
+	return q;
+}
+
 /*
  * start a new Prog list.
  */
@@ -125,6 +138,64 @@ 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