cmd/compile: extract inline related fields into separate Inline type

Inl, Inldcl, and InlCost are only applicable to functions with bodies
that can be inlined, so pull them out into a separate Inline type to
make understanding them easier.

A side benefit is that we can check if a function can be inlined by
just checking if n.Func.Inl is non-nil, which simplifies handling of
empty function bodies.

While here, remove some unnecessary Curfn twiddling, and make imported
functions use Inl.Dcl instead of Func.Dcl for consistency for local
functions.

Passes toolstash-check.

Change-Id: Ifd4a80349d85d9e8e4484952b38ec4a63182e81f
Reviewed-on: https://go-review.googlesource.com/104756
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

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

@@ -377,11 +377,11 @@ func export(out *bufio.Writer, trace bool) int {
 			// function has inlineable body:
 			// write index and body
 			if p.trace {
-				p.tracef("\n----\nfunc { %#v }\n", f.Inl)
+				p.tracef("\n----\nfunc { %#v }\n", asNodes(f.Inl.Body))
 			}
 			p.int(i)
-			p.int(int(f.InlCost))
-			p.stmtList(f.Inl)
+			p.int(int(f.Inl.Cost))
+			p.stmtList(asNodes(f.Inl.Body))
 			if p.trace {
 				p.tracef("\n")
 			}

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

@@ -188,28 +188,22 @@ func Import(imp *types.Pkg, in *bufio.Reader) {
 		// parameter renaming which doesn't matter if we don't have a body.
 
 		inlCost := p.int()
-		if f := p.funcList[i]; f != nil && f.Func.Inl.Len() == 0 {
+		if f := p.funcList[i]; f != nil && f.Func.Inl == nil {
 			// function not yet imported - read body and set it
 			funchdr(f)
 			body := p.stmtList()
-			if body == nil {
-				// Make sure empty body is not interpreted as
-				// no inlineable body (see also parser.fnbody)
-				// (not doing so can cause significant performance
-				// degradation due to unnecessary calls to empty
-				// functions).
-				body = []*Node{nod(OEMPTY, nil, nil)}
-			}
-			f.Func.Inl.Set(body)
-			f.Func.InlCost = int32(inlCost)
-			if Debug['E'] > 0 && Debug['m'] > 2 && f.Func.Inl.Len() != 0 {
-				if Debug['m'] > 3 {
-					fmt.Printf("inl body for %v: %+v\n", f, f.Func.Inl)
-				} else {
-					fmt.Printf("inl body for %v: %v\n", f, f.Func.Inl)
-				}
-			}
 			funcbody()
+			f.Func.Inl = &Inline{
+				Cost: int32(inlCost),
+				Body: body,
+			}
+			if Debug['E'] > 0 && Debug['m'] > 2 {
+				if Debug['m'] > 3 {
+					fmt.Printf("inl body for %v: %+v\n", f, asNodes(body))
+				} else {
+					fmt.Printf("inl body for %v: %v\n", f, asNodes(body))
+				}
+			}
 		} else {
 			// function already imported - read body but discard declarations
 			dclcontext = PDISCARD // throw away any declarations

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

@@ -70,7 +70,7 @@ func typecheckinl(fn *Node) {
 	}
 
 	if Debug['m'] > 2 || Debug_export != 0 {
-		fmt.Printf("typecheck import [%v] %L { %#v }\n", fn.Sym, fn, fn.Func.Inl)
+		fmt.Printf("typecheck import [%v] %L { %#v }\n", fn.Sym, fn, asNodes(fn.Func.Inl.Body))
 	}
 
 	save_safemode := safemode
@@ -78,9 +78,16 @@ func typecheckinl(fn *Node) {
 
 	savefn := Curfn
 	Curfn = fn
-	typecheckslice(fn.Func.Inl.Slice(), Etop)
+	typecheckslice(fn.Func.Inl.Body, Etop)
 	Curfn = savefn
 
+	// During typechecking, declarations are added to
+	// Curfn.Func.Dcl. Move them to Inl.Dcl for consistency with
+	// how local functions behave. (Append because typecheckinl
+	// may be called multiple times.)
+	fn.Func.Inl.Dcl = append(fn.Func.Inl.Dcl, fn.Func.Dcl...)
+	fn.Func.Dcl = nil
+
 	safemode = save_safemode
 
 	lineno = lno
@@ -155,26 +162,21 @@ func caninl(fn *Node) {
 		return
 	}
 
-	savefn := Curfn
-	Curfn = fn
-
-	n.Func.Inl.Set(fn.Nbody.Slice())
-	fn.Nbody.Set(inlcopylist(n.Func.Inl.Slice()))
-	inldcl := inlcopylist(n.Name.Defn.Func.Dcl)
-	n.Func.Inldcl.Set(inldcl)
-	n.Func.InlCost = maxBudget - visitor.budget
+	n.Func.Inl = &Inline{
+		Cost: maxBudget - visitor.budget,
+		Dcl:  inlcopylist(n.Name.Defn.Func.Dcl),
+		Body: inlcopylist(fn.Nbody.Slice()),
+	}
 
 	// hack, TODO, check for better way to link method nodes back to the thing with the ->inl
 	// this is so export can find the body of a method
 	fn.Type.FuncType().Nname = asTypesNode(n)
 
 	if Debug['m'] > 1 {
-		fmt.Printf("%v: can inline %#v as: %#v { %#v }\n", fn.Line(), n, fn.Type, n.Func.Inl)
+		fmt.Printf("%v: can inline %#v as: %#v { %#v }\n", fn.Line(), n, fn.Type, asNodes(n.Func.Inl.Body))
 	} else if Debug['m'] != 0 {
 		fmt.Printf("%v: can inline %v\n", fn.Line(), n)
 	}
-
-	Curfn = savefn
 }
 
 // inlFlood marks n's inline body for export and recursively ensures
@@ -189,7 +191,7 @@ func inlFlood(n *Node) {
 	if n.Func == nil {
 		Fatalf("inlFlood: missing Func on %v", n)
 	}
-	if n.Func.Inl.Len() == 0 {
+	if n.Func.Inl == nil {
 		return
 	}
 
@@ -200,7 +202,7 @@ func inlFlood(n *Node) {
 
 	typecheckinl(n)
 
-	inspectList(n.Func.Inl, func(n *Node) bool {
+	inspectList(asNodes(n.Func.Inl.Body), func(n *Node) bool {
 		switch n.Op {
 		case ONAME:
 			// Mark any referenced global variables or
@@ -259,13 +261,13 @@ func (v *hairyVisitor) visit(n *Node) bool {
 			}
 		}
 
-		if fn := n.Left.Func; fn != nil && fn.Inl.Len() != 0 {
-			v.budget -= fn.InlCost
+		if fn := n.Left.Func; fn != nil && fn.Inl != nil {
+			v.budget -= fn.Inl.Cost
 			break
 		}
 		if n.Left.isMethodExpression() {
-			if d := asNode(n.Left.Sym.Def); d != nil && d.Func.Inl.Len() != 0 {
-				v.budget -= d.Func.InlCost
+			if d := asNode(n.Left.Sym.Def); d != nil && d.Func.Inl != nil {
+				v.budget -= d.Func.Inl.Cost
 				break
 			}
 		}
@@ -300,8 +302,8 @@ func (v *hairyVisitor) visit(n *Node) bool {
 				break
 			}
 		}
-		if inlfn := asNode(t.FuncType().Nname).Func; inlfn.Inl.Len() != 0 {
-			v.budget -= inlfn.InlCost
+		if inlfn := asNode(t.FuncType().Nname).Func; inlfn.Inl != nil {
+			v.budget -= inlfn.Inl.Cost
 			break
 		}
 		if Debug['l'] < 4 {
@@ -394,7 +396,7 @@ func inlcopy(n *Node) *Node {
 
 	m := n.copy()
 	if m.Func != nil {
-		m.Func.Inl.Set(nil)
+		Fatalf("unexpected Func: %v", m)
 	}
 	m.Left = inlcopy(n.Left)
 	m.Right = inlcopy(n.Right)
@@ -583,7 +585,7 @@ func inlnode(n *Node) *Node {
 		if Debug['m'] > 3 {
 			fmt.Printf("%v:call to func %+v\n", n.Line(), n.Left)
 		}
-		if n.Left.Func != nil && n.Left.Func.Inl.Len() != 0 && !isIntrinsicCall(n) { // normal case
+		if n.Left.Func != nil && n.Left.Func.Inl != nil && !isIntrinsicCall(n) { // normal case
 			n = mkinlcall(n, n.Left)
 		} else if n.Left.isMethodExpression() && asNode(n.Left.Sym.Def) != nil {
 			n = mkinlcall(n, asNode(n.Left.Sym.Def))
@@ -647,7 +649,7 @@ func inlinableClosure(n *Node) *Node {
 	c := n.Func.Closure
 	caninl(c)
 	f := c.Func.Nname
-	if f == nil || f.Func.Inl.Len() == 0 {
+	if f == nil || f.Func.Inl == nil {
 		return nil
 	}
 	return f
@@ -772,7 +774,7 @@ var inlgen int
 // The result of mkinlcall1 MUST be assigned back to n, e.g.
 // 	n.Left = mkinlcall1(n.Left, fn, isddd)
 func mkinlcall1(n, fn *Node) *Node {
-	if fn.Func.Inl.Len() == 0 {
+	if fn.Func.Inl == nil {
 		// No inlinable body.
 		return n
 	}
@@ -798,7 +800,7 @@ func mkinlcall1(n, fn *Node) *Node {
 
 	// We have a function node, and it has an inlineable body.
 	if Debug['m'] > 1 {
-		fmt.Printf("%v: inlining call to %v %#v { %#v }\n", n.Line(), fn.Sym, fn.Type, fn.Func.Inl)
+		fmt.Printf("%v: inlining call to %v %#v { %#v }\n", n.Line(), fn.Sym, fn.Type, asNodes(fn.Func.Inl.Body))
 	} else if Debug['m'] != 0 {
 		fmt.Printf("%v: inlining call to %v\n", n.Line(), fn)
 	}
@@ -814,12 +816,8 @@ func mkinlcall1(n, fn *Node) *Node {
 	// record formals/locals for later post-processing
 	var inlfvars []*Node
 
-	// Find declarations corresponding to inlineable body.
-	var dcl []*Node
+	// Handle captured variables when inlining closures.
 	if fn.Name.Defn != nil {
-		dcl = fn.Func.Inldcl.Slice() // local function
-
-		// handle captured variables when inlining closures
 		if c := fn.Name.Defn.Func.Closure; c != nil {
 			for _, v := range c.Func.Closure.Func.Cvars.Slice() {
 				if v.Op == OXXX {
@@ -854,11 +852,9 @@ func mkinlcall1(n, fn *Node) *Node {
 				}
 			}
 		}
-	} else {
-		dcl = fn.Func.Dcl // imported function
 	}
 
-	for _, ln := range dcl {
+	for _, ln := range fn.Func.Inl.Dcl {
 		if ln.Op != ONAME {
 			continue
 		}
@@ -1020,7 +1016,7 @@ func mkinlcall1(n, fn *Node) *Node {
 		newInlIndex: newIndex,
 	}
 
-	body := subst.list(fn.Func.Inl)
+	body := subst.list(asNodes(fn.Func.Inl.Body))
 
 	lab := nod(OLABEL, retlabel, nil)
 	body = append(body, lab)

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

@@ -544,7 +544,7 @@ func Main(archInit func(*Arch)) {
 		// Typecheck imported function bodies if debug['l'] > 1,
 		// otherwise lazily when used or re-exported.
 		for _, n := range importlist {
-			if n.Func.Inl.Len() != 0 {
+			if n.Func.Inl != nil {
 				saveerrors()
 				typecheckinl(n)
 			}

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

@@ -570,13 +570,8 @@ func createDwarfVars(fnsym *obj.LSym, fn *Func, automDecls []*Node) ([]*Node, []
 // with local vars; disregard this versioning when sorting.
 func preInliningDcls(fnsym *obj.LSym) []*Node {
 	fn := Ctxt.DwFixups.GetPrecursorFunc(fnsym).(*Node)
-	var dcl, rdcl []*Node
-	if fn.Name.Defn != nil {
-		dcl = fn.Func.Inldcl.Slice() // local function
-	} else {
-		dcl = fn.Func.Dcl // imported function
-	}
-	for _, n := range dcl {
+	var rdcl []*Node
+	for _, n := range fn.Func.Inl.Dcl {
 		c := n.Sym.Name[0]
 		// Avoid reporting "_" parameters, since if there are more than
 		// one, it can result in a collision later on, as in #23179.

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

@@ -22,7 +22,7 @@ func TestSizeof(t *testing.T) {
 		_32bit uintptr     // size on 32bit platforms
 		_64bit uintptr     // size on 64bit platforms
 	}{
-		{Func{}, 124, 224},
+		{Func{}, 116, 208},
 		{Name{}, 32, 56},
 		{Param{}, 24, 48},
 		{Node{}, 76, 128},

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

@@ -461,7 +461,6 @@ type Func struct {
 	Exit      Nodes
 	Cvars     Nodes   // closure params
 	Dcl       []*Node // autodcl for this func/closure
-	Inldcl    Nodes   // copy of dcl for use in inlining
 
 	// Parents records the parent scope of each scope within a
 	// function. The root scope (0) has no parent, so the i'th
@@ -484,8 +483,7 @@ type Func struct {
 	Nname      *Node
 	lsym       *obj.LSym
 
-	Inl     Nodes // copy of the body for use in inlining
-	InlCost int32
+	Inl *Inline
 
 	Label int32 // largest auto-generated label in this function
 
@@ -502,6 +500,15 @@ type Func struct {
 	nwbrCalls *[]nowritebarrierrecCallSym
 }
 
+// An Inline holds fields used for function bodies that can be inlined.
+type Inline struct {
+	Cost int32 // heuristic cost of inlining this function
+
+	// Copies of Func.Dcl and Nbody for use during inlining.
+	Dcl  []*Node
+	Body []*Node
+}
+
 // A Mark represents a scope boundary.
 type Mark struct {
 	// Pos is the position of the token that marks the scope
@@ -737,6 +744,11 @@ const (
 // a slice to save space.
 type Nodes struct{ slice *[]*Node }
 
+// asNodes returns a slice of *Node as a Nodes value.
+func asNodes(s []*Node) Nodes {
+	return Nodes{&s}
+}
+
 // Slice returns the entries in Nodes as a slice.
 // Changes to the slice entries (as in s[i] = n) will be reflected in
 // the Nodes.