cmd/compile: do not mark arrays used for map initialization noalg

Arrays marked noalg are created by the compiler to hold keys and values
to initialize map literals. The ssa backend creates a pointer type for
the array type when creating an OpAddr while processing the loop that
initializes the map from the arrays. The pointer type does not inherit
the noalg property but points to the noalg array type.

This causes values created through reflect of types that should be
equal to compare unequal because the noalg and alg type might be
compared and these are not the same.

A similar problem occurred in #32595 for argument arrays of defer structs.

Created #47904 to track improve noalg handling to be able to
reintroduce this optimization again.

Fixes #47068

Change-Id: I87549342bd404b98d71a3c0f33e3c169e9d4efc8
Reviewed-on: https://go-review.googlesource.com/c/go/+/344349
Trust: Martin Möhrmann <martin@golang.org>
Run-TryBot: Martin Möhrmann <martin@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/cmd/compile/internal/walk/complit.go

@@ -440,8 +440,8 @@ func maplit(n *ir.CompLitExpr, m ir.Node, init *ir.Nodes) {
 		tk := types.NewArray(n.Type().Key(), int64(len(entries)))
 		te := types.NewArray(n.Type().Elem(), int64(len(entries)))
 
-		tk.SetNoalg(true)
-		te.SetNoalg(true)
+		// TODO(#47904): mark tk and te NoAlg here once the
+		// compiler/linker can handle NoAlg types correctly.
 
 		types.CalcSize(tk)
 		types.CalcSize(te)

test/fixedbugs/issue47068.dir/a.go

@@ -0,0 +1,15 @@
+// Copyright 2021 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
+
+func A() {
+	var m map[int]int = map[int]int{
+		0: 0, 1: 0, 2: 0, 3: 0, 4: 0, 5: 0, 6: 0, 7: 0, 8: 0, 9: 0,
+		10: 0, 11: 0, 12: 0, 13: 0, 14: 0, 15: 0, 16: 0, 17: 0, 18: 0, 19: 0,
+		20: 0, 21: 0, 22: 0, 23: 0, 24: 0, 25: 0, 26: 0, 27: 0, 28: 0, 29: 0}
+	if len(m) != 30 {
+		panic("unepexted map length")
+	}
+}

test/fixedbugs/issue47068.dir/b.go

@@ -0,0 +1,15 @@
+// Copyright 2021 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 "reflect"
+
+func B() {
+	t1 := reflect.TypeOf([30]int{})
+	t2 := reflect.TypeOf(new([30]int)).Elem()
+	if t1 != t2 {
+		panic("[30]int types do not match")
+	}
+}

test/fixedbugs/issue47068.dir/main.go

@@ -0,0 +1,15 @@
+// Copyright 2021 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 main
+
+import (
+	"a"
+	"b"
+)
+
+func main() {
+	a.A()
+	b.B()
+}

test/fixedbugs/issue47068.go

@@ -0,0 +1,7 @@
+// rundir
+
+// Copyright 2019 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