cmd/compile: disable inlining functions with closures for now

Added a flag '-d=inlfuncswithclosures=1' to allow inlining functions with
closures, and change the default to off for now, until #44370 is fixed.

Updates #44370.

Change-Id: Ic17723aa5c091d91f5f5004d8b63ec7125257acf
Reviewed-on: https://go-review.googlesource.com/c/go/+/296049
Run-TryBot: Dan Scales <danscales@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Dan Scales <danscales@google.com>

src/cmd/compile/internal/base/debug.go

@@ -40,6 +40,7 @@ type DebugFlags struct {
 	Export               int    `help:"print export data"`
 	Fieldtrack           *int   `help:"enable field tracking"`
 	GCProg               int    `help:"print dump of GC programs"`
+	InlFuncsWithClosures int    `help:"allow functions with closures to be inlined"`
 	Libfuzzer            int    `help:"enable coverage instrumentation for libfuzzer"`
 	LocationLists        int    `help:"print information about DWARF location list creation"`
 	Nil                  int    `help:"print information about nil checks"`

src/cmd/compile/internal/inline/inl.go

@@ -354,15 +354,15 @@ func (v *hairyVisitor) doNode(n ir.Node) bool {
 		return true
 
 	case ir.OCLOSURE:
-		// TODO(danscales,mdempsky): Get working with -G.
-		// Probably after #43818 is fixed.
-		if base.Flag.G > 0 {
-			v.reason = "inlining closures not yet working with -G"
+		if base.Debug.InlFuncsWithClosures == 0 {
+			// TODO(danscales): change default of InlFuncsWithClosures
+			// to 1 when #44370 is fixed
+			v.reason = "not inlining functions with closures"
 			return true
 		}
 
-		// TODO(danscales) - fix some bugs when budget is lowered below 15
-		// Maybe make budget proportional to number of closure variables, e.g.:
+		// TODO(danscales): Maybe make budget proportional to number of closure
+		// variables, e.g.:
 		//v.budget -= int32(len(n.(*ir.ClosureExpr).Func.ClosureVars) * 3)
 		v.budget -= 15
 		// Scan body of closure (which DoChildren doesn't automatically

test/closure3.go

@@ -1,4 +1,4 @@
-// errorcheckandrundir -0 -m
+// errorcheckandrundir -0 -m -d=inlfuncswithclosures=1
 
 // Copyright 2017 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style

test/inline.go

@@ -1,4 +1,4 @@
-// errorcheck -0 -m
+// errorcheck -0 -m -d=inlfuncswithclosures=1
 
 // Copyright 2015 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style