cmd/compile: run checkbce after fuseLate pass

So the bounds check which are eliminated during late fuse pass could be
detected correctly.

Fixes #67329

Change-Id: Id7992fbb8c26e0d43e7db66a0a3a2c0d9ed937a8
Reviewed-on: https://go-review.googlesource.com/c/go/+/598635
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/cmd/compile/internal/ssa/checkbce.go

@@ -16,6 +16,9 @@ func checkbce(f *Func) {
 	}
 
 	for _, b := range f.Blocks {
+		if b.Kind == BlockInvalid {
+			continue
+		}
 		for _, v := range b.Values {
 			if v.Op == OpIsInBounds || v.Op == OpIsSliceInBounds {
 				if f.pass.debug > 0 {

src/cmd/compile/internal/ssa/compile.go

@@ -477,9 +477,9 @@ var passes = [...]pass{
 	{name: "dead auto elim", fn: elimDeadAutosGeneric},
 	{name: "sccp", fn: sccp},
 	{name: "generic deadcode", fn: deadcode, required: true}, // remove dead stores, which otherwise mess up store chain
-	{name: "check bce", fn: checkbce},
 	{name: "branchelim", fn: branchelim},
 	{name: "late fuse", fn: fuseLate},
+	{name: "check bce", fn: checkbce},
 	{name: "dse", fn: dse},
 	{name: "memcombine", fn: memcombine},
 	{name: "writebarrier", fn: writebarrier, required: true}, // expand write barrier ops

test/fixedbugs/issue67329.go

@@ -0,0 +1,27 @@
+// errorcheck -0 -d=ssa/check_bce/debug=1
+
+// Copyright 2024 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 x
+
+func Found(x []string) string {
+	switch len(x) {
+	default:
+		return x[0]
+	case 0, 1:
+		return ""
+	}
+}
+
+func NotFound(x []string) string {
+	switch len(x) {
+	default:
+		return x[0]
+	case 0:
+		return ""
+	case 1:
+		return ""
+	}
+}