cmd/compile: loop to ensure all autogenerated functions are compiled

I was wrong. There was a need to loop here.

Fixes #24761

Change-Id: If13b3ab72febde930bdaebdddd1c05e0d0446020
Reviewed-on: https://go-review.googlesource.com/105615
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/cmd/compile/internal/gc/obj.go

@@ -144,16 +144,17 @@ func dumpLinkerObj(bout *bio.Writer) {
 	dumpimportstrings()
 	dumpbasictypes()
 
-	// The first call to dumpsignats can generate functions,
+	// Calls to dumpsignats can generate functions,
 	// like method wrappers and hash and equality routines.
-	compileFunctions()
-
-	// Process any new signats added during compilation.
-	// No need to loop here; signats from compiling the generated
-	// functions should not themselves generate new functions.
-	// If they do, we'll know about it; the sanity check of
-	// len(compilequeue) in gc.Main will fail.
-	dumpsignats()
+	// Compile any generated functions, process any new resulting types, repeat.
+	// This can't loop forever, because there is no way to generate an infinite
+	// number of types in a finite amount of code.
+	// In the typical case, we loop 0 or 1 times.
+	// It was not until issue 24761 that we found any code that required a loop at all.
+	for len(compilequeue) > 0 {
+		compileFunctions()
+		dumpsignats()
+	}
 
 	// Dump extra globals.
 	tmp := externdcl

test/fixedbugs/issue24761.dir/a.go

+// Copyright 2018 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
+
+type T2 struct{}
+
+func (t *T2) M2(a, b float64) {
+	variadic(a, b)
+}
+
+func variadic(points ...float64) {
+	println(points)
+}

test/fixedbugs/issue24761.dir/b.go

+// Copyright 2018 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"
+
+type T1 struct {
+	*a.T2
+}

test/fixedbugs/issue24761.go

+// compiledir -c=4
+
+// Copyright 2018 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 ignored