diff --git a/src/cmd/internal/obj/x86/obj6.go b/src/cmd/internal/obj/x86/obj6.go
index 7738d79b1b..c479a07fe4 100644
--- a/src/cmd/internal/obj/x86/obj6.go
+++ b/src/cmd/internal/obj/x86/obj6.go
@@ -660,8 +660,13 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 		for q := p; q != nil; q = q.Link {
 			switch q.As {
 			case obj.ACALL:
-				leaf = false
-				break LeafSearch
+				// Treat common runtime calls that take no arguments
+				// the same as duffcopy and duffzero.
+				if !isZeroArgRuntimeCall(q.To.Sym) {
+					leaf = false
+					break LeafSearch
+				}
+				fallthrough
 			case obj.ADUFFCOPY, obj.ADUFFZERO:
 				if autoffset >= obj.StackSmall-8 {
 					leaf = false
@@ -928,6 +933,17 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 	}
 }
 
+func isZeroArgRuntimeCall(s *obj.LSym) bool {
+	if s == nil {
+		return false
+	}
+	switch s.Name {
+	case "runtime.panicindex", "runtime.panicslice", "runtime.panicdivide":
+		return true
+	}
+	return false
+}
+
 func indir_cx(ctxt *obj.Link, p *obj.Prog, a *obj.Addr) {
 	if ctxt.Headtype == obj.Hnacl && p.Mode == 64 {
 		a.Type = obj.TYPE_MEM