cmd/gc: generate type alg after calling dowidth.

Previously it might happen before calling dowidth and
result in a compiler crash.

Fixes #8060.

LGTM=dvyukov, rsc
R=golang-codereviews, dvyukov, gobot, rsc
CC=golang-codereviews
https://golang.org/cl/110980044

src/cmd/gc/reflect.c

@@ -727,12 +727,12 @@ dcommontype(Sym *s, int ot, Type *t)
 	sizeofAlg = 2*widthptr;
 	if(algarray == nil)
 		algarray = pkglookup("algarray", runtimepkg);
+	dowidth(t);
 	alg = algtype(t);
 	algsym = S;
 	if(alg < 0)
 		algsym = dalgsym(t);
 
-	dowidth(t);
 	if(t->sym != nil && !isptr[t->etype])
 		sptr = dtypesym(ptrto(t));
 	else

test/fixedbugs/issue8060.dir/a.go

+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+var A = []*[2][1]float64{}

test/fixedbugs/issue8060.dir/b.go

+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package b
+
+import "a"
+
+var X = a.A
+
+func b() {
+	_ = [3][1]float64{}
+}

test/fixedbugs/issue8060.go

+// compiledir
+
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Issue 8060: internal compiler error.
+
+package ignored