src/cmd/compile/internal/ir/func.go - go - Git at Google

 // Copyright 2020 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 ir

 import (
 	"cmd/compile/internal/base"
 	"cmd/compile/internal/types"
 	"cmd/internal/obj"
 	"cmd/internal/src"
 	"fmt"
 )

 // A Func corresponds to a single function in a Go program
 // (and vice versa: each function is denoted by exactly one *Func).
 //
 // There are multiple nodes that represent a Func in the IR.
 //
 // The ONAME node (Func.Nname) is used for plain references to it.
 // The ODCLFUNC node (the Func itself) is used for its declaration code.
 // The OCLOSURE node (Func.OClosure) is used for a reference to a
 // function literal.
 //
 // An imported function will have an ONAME node which points to a Func
 // with an empty body.
 // A declared function or method has an ODCLFUNC (the Func itself) and an ONAME.
 // A function literal is represented directly by an OCLOSURE, but it also
 // has an ODCLFUNC (and a matching ONAME) representing the compiled
 // underlying form of the closure, which accesses the captured variables
 // using a special data structure passed in a register.
 //
 // A method declaration is represented like functions, except f.Sym
 // will be the qualified method name (e.g., "T.m") and
 // f.Func.Shortname is the bare method name (e.g., "m").
 //
 // A method expression (T.M) is represented as an OMETHEXPR node,
 // in which n.Left and n.Right point to the type and method, respectively.
 // Each distinct mention of a method expression in the source code
 // constructs a fresh node.
 //
 // A method value (t.M) is represented by ODOTMETH/ODOTINTER
 // when it is called directly and by OMETHVALUE otherwise.
 // These are like method expressions, except that for ODOTMETH/ODOTINTER,
 // the method name is stored in Sym instead of Right.
 // Each OMETHVALUE ends up being implemented as a new
 // function, a bit like a closure, with its own ODCLFUNC.
 // The OMETHVALUE uses n.Func to record the linkage to
 // the generated ODCLFUNC, but there is no
 // pointer from the Func back to the OMETHVALUE.
 type Func struct {
 	miniNode
 	Body Nodes
 	Iota int64

 	Nname    *Name        // ONAME node
 	OClosure *ClosureExpr // OCLOSURE node

 	Shortname *types.Sym

 	// Extra entry code for the function. For example, allocate and initialize
 	// memory for escaping parameters.
 	Enter Nodes
 	Exit  Nodes

 	// ONAME nodes for all params/locals for this func/closure, does NOT
 	// include closurevars until transforming closures during walk.
 	// Names must be listed PPARAMs, PPARAMOUTs, then PAUTOs,
 	// with PPARAMs and PPARAMOUTs in order corresponding to the function signature.
 	// However, as anonymous or blank PPARAMs are not actually declared,
 	// they are omitted from Dcl.
 	// Anonymous and blank PPARAMOUTs are declared as ~rNN and ~bNN Names, respectively.
 	Dcl []*Name

 	// ClosureVars lists the free variables that are used within a
 	// function literal, but formally declared in an enclosing
 	// function. The variables in this slice are the closure function's
 	// own copy of the variables, which are used within its function
 	// body. They will also each have IsClosureVar set, and will have
 	// Byval set if they're captured by value.
 	ClosureVars []*Name

 	// Enclosed functions that need to be compiled.
 	// Populated during walk.
 	Closures []*Func

 	// Parents records the parent scope of each scope within a
 	// function. The root scope (0) has no parent, so the i'th
 	// scope's parent is stored at Parents[i-1].
 	Parents []ScopeID

 	// Marks records scope boundary changes.
 	Marks []Mark

 	FieldTrack map[*obj.LSym]struct{}
 	DebugInfo  interface{}
 	LSym       *obj.LSym // Linker object in this function's native ABI (Func.ABI)

 	Inl *Inline

 	// Closgen tracks how many closures have been generated within
 	// this function. Used by closurename for creating unique
 	// function names.
 	Closgen int32

 	Label int32 // largest auto-generated label in this function

 	Endlineno src.XPos
 	WBPos     src.XPos // position of first write barrier; see SetWBPos

 	Pragma PragmaFlag // go:xxx function annotations

 	flags bitset16

 	// ABI is a function's "definition" ABI. This is the ABI that
 	// this function's generated code is expecting to be called by.
 	//
 	// For most functions, this will be obj.ABIInternal. It may be
 	// a different ABI for functions defined in assembly or ABI wrappers.
 	//
 	// This is included in the export data and tracked across packages.
 	ABI obj.ABI
 	// ABIRefs is the set of ABIs by which this function is referenced.
 	// For ABIs other than this function's definition ABI, the
 	// compiler generates ABI wrapper functions. This is only tracked
 	// within a package.
 	ABIRefs obj.ABISet

 	NumDefers  int32 // number of defer calls in the function
 	NumReturns int32 // number of explicit returns in the function

 	// nwbrCalls records the LSyms of functions called by this
 	// function for go:nowritebarrierrec analysis. Only filled in
 	// if nowritebarrierrecCheck != nil.
 	NWBRCalls *[]SymAndPos
 }

 func NewFunc(pos src.XPos) *Func {
 	f := new(Func)
 	f.pos = pos
 	f.op = ODCLFUNC
 	f.Iota = -1
 	// Most functions are ABIInternal. The importer or symabis
 	// pass may override this.
 	f.ABI = obj.ABIInternal
 	return f
 }

 func (f *Func) isStmt() {}

 func (n *Func) copy() Node                         { panic(n.no("copy")) }
 func (n *Func) doChildren(do func(Node) bool) bool { return doNodes(n.Body, do) }
 func (n *Func) editChildren(edit func(Node) Node)  { editNodes(n.Body, edit) }

 func (f *Func) Type() *types.Type                { return f.Nname.Type() }
 func (f *Func) Sym() *types.Sym                  { return f.Nname.Sym() }
 func (f *Func) Linksym() *obj.LSym               { return f.Nname.Linksym() }
 func (f *Func) LinksymABI(abi obj.ABI) *obj.LSym { return f.Nname.LinksymABI(abi) }

 // 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 Func.Body for use during inlining. Copies are
 	// needed because the function's dcl/body may be changed by later compiler
 	// transformations. These fields are also populated when a function from
 	// another package is imported.
 	Dcl  []*Name
 	Body []Node

 	// CanDelayResults reports whether it's safe for the inliner to delay
 	// initializing the result parameters until immediately before the
 	// "return" statement.
 	CanDelayResults bool
 }

 // A Mark represents a scope boundary.
 type Mark struct {
 	// Pos is the position of the token that marks the scope
 	// change.
 	Pos src.XPos

 	// Scope identifies the innermost scope to the right of Pos.
 	Scope ScopeID
 }

 // A ScopeID represents a lexical scope within a function.
 type ScopeID int32

 const (
 	funcDupok         = 1 << iota // duplicate definitions ok
 	funcWrapper                   // hide frame from users (elide in tracebacks, don't count as a frame for recover())
 	funcABIWrapper                // is an ABI wrapper (also set flagWrapper)
 	funcNeedctxt                  // function uses context register (has closure variables)
 	funcReflectMethod             // function calls reflect.Type.Method or MethodByName
 	// true if closure inside a function; false if a simple function or a
 	// closure in a global variable initialization
 	funcIsHiddenClosure
 	funcIsDeadcodeClosure        // true if closure is deadcode
 	funcHasDefer                 // contains a defer statement
 	funcNilCheckDisabled         // disable nil checks when compiling this function
 	funcInlinabilityChecked      // inliner has already determined whether the function is inlinable
 	funcExportInline             // include inline body in export data
 	funcInstrumentBody           // add race/msan/asan instrumentation during SSA construction
 	funcOpenCodedDeferDisallowed // can't do open-coded defers
 	funcClosureCalled            // closure is only immediately called; used by escape analysis
 )

 type SymAndPos struct {
 	Sym *obj.LSym // LSym of callee
 	Pos src.XPos  // line of call
 }

 func (f *Func) Dupok() bool                    { return f.flags&funcDupok != 0 }
 func (f *Func) Wrapper() bool                  { return f.flags&funcWrapper != 0 }
 func (f *Func) ABIWrapper() bool               { return f.flags&funcABIWrapper != 0 }
 func (f *Func) Needctxt() bool                 { return f.flags&funcNeedctxt != 0 }
 func (f *Func) ReflectMethod() bool            { return f.flags&funcReflectMethod != 0 }
 func (f *Func) IsHiddenClosure() bool          { return f.flags&funcIsHiddenClosure != 0 }
 func (f *Func) IsDeadcodeClosure() bool        { return f.flags&funcIsDeadcodeClosure != 0 }
 func (f *Func) HasDefer() bool                 { return f.flags&funcHasDefer != 0 }
 func (f *Func) NilCheckDisabled() bool         { return f.flags&funcNilCheckDisabled != 0 }
 func (f *Func) InlinabilityChecked() bool      { return f.flags&funcInlinabilityChecked != 0 }
 func (f *Func) ExportInline() bool             { return f.flags&funcExportInline != 0 }
 func (f *Func) InstrumentBody() bool           { return f.flags&funcInstrumentBody != 0 }
 func (f *Func) OpenCodedDeferDisallowed() bool { return f.flags&funcOpenCodedDeferDisallowed != 0 }
 func (f *Func) ClosureCalled() bool            { return f.flags&funcClosureCalled != 0 }

 func (f *Func) SetDupok(b bool)                    { f.flags.set(funcDupok, b) }
 func (f *Func) SetWrapper(b bool)                  { f.flags.set(funcWrapper, b) }
 func (f *Func) SetABIWrapper(b bool)               { f.flags.set(funcABIWrapper, b) }
 func (f *Func) SetNeedctxt(b bool)                 { f.flags.set(funcNeedctxt, b) }
 func (f *Func) SetReflectMethod(b bool)            { f.flags.set(funcReflectMethod, b) }
 func (f *Func) SetIsHiddenClosure(b bool)          { f.flags.set(funcIsHiddenClosure, b) }
 func (f *Func) SetIsDeadcodeClosure(b bool)        { f.flags.set(funcIsDeadcodeClosure, b) }
 func (f *Func) SetHasDefer(b bool)                 { f.flags.set(funcHasDefer, b) }
 func (f *Func) SetNilCheckDisabled(b bool)         { f.flags.set(funcNilCheckDisabled, b) }
 func (f *Func) SetInlinabilityChecked(b bool)      { f.flags.set(funcInlinabilityChecked, b) }
 func (f *Func) SetExportInline(b bool)             { f.flags.set(funcExportInline, b) }
 func (f *Func) SetInstrumentBody(b bool)           { f.flags.set(funcInstrumentBody, b) }
 func (f *Func) SetOpenCodedDeferDisallowed(b bool) { f.flags.set(funcOpenCodedDeferDisallowed, b) }
 func (f *Func) SetClosureCalled(b bool)            { f.flags.set(funcClosureCalled, b) }

 func (f *Func) SetWBPos(pos src.XPos) {
 	if base.Debug.WB != 0 {
 		base.WarnfAt(pos, "write barrier")
 	}
 	if !f.WBPos.IsKnown() {
 		f.WBPos = pos
 	}
 }

 // FuncName returns the name (without the package) of the function n.
 func FuncName(f *Func) string {
 	if f == nil || f.Nname == nil {
 		return "<nil>"
 	}
 	return f.Sym().Name
 }

 // PkgFuncName returns the name of the function referenced by n, with package prepended.
 // This differs from the compiler's internal convention where local functions lack a package
 // because the ultimate consumer of this is a human looking at an IDE; package is only empty
 // if the compilation package is actually the empty string.
 func PkgFuncName(f *Func) string {
 	if f == nil || f.Nname == nil {
 		return "<nil>"
 	}
 	s := f.Sym()
 	pkg := s.Pkg

 	p := base.Ctxt.Pkgpath
 	if pkg != nil && pkg.Path != "" {
 		p = pkg.Path
 	}
 	if p == "" {
 		return s.Name
 	}
 	return p + "." + s.Name
 }

 var CurFunc *Func

 // WithFunc invokes do with CurFunc and base.Pos set to curfn and
 // curfn.Pos(), respectively, and then restores their previous values
 // before returning.
 func WithFunc(curfn *Func, do func()) {
 	oldfn, oldpos := CurFunc, base.Pos
 	defer func() { CurFunc, base.Pos = oldfn, oldpos }()

 	CurFunc, base.Pos = curfn, curfn.Pos()
 	do()
 }

 func FuncSymName(s *types.Sym) string {
 	return s.Name + "·f"
 }

 // MarkFunc marks a node as a function.
 func MarkFunc(n *Name) {
 	if n.Op() != ONAME || n.Class != Pxxx {
 		base.FatalfAt(n.Pos(), "expected ONAME/Pxxx node, got %v (%v/%v)", n, n.Op(), n.Class)
 	}

 	n.Class = PFUNC
 	n.Sym().SetFunc(true)
 }

 // ClosureDebugRuntimeCheck applies boilerplate checks for debug flags
 // and compiling runtime
 func ClosureDebugRuntimeCheck(clo *ClosureExpr) {
 	if base.Debug.Closure > 0 {
 		if clo.Esc() == EscHeap {
 			base.WarnfAt(clo.Pos(), "heap closure, captured vars = %v", clo.Func.ClosureVars)
 		} else {
 			base.WarnfAt(clo.Pos(), "stack closure, captured vars = %v", clo.Func.ClosureVars)
 		}
 	}
 	if base.Flag.CompilingRuntime && clo.Esc() == EscHeap && !clo.IsGoWrap {
 		base.ErrorfAt(clo.Pos(), "heap-allocated closure %s, not allowed in runtime", FuncName(clo.Func))
 	}
 }

 // IsTrivialClosure reports whether closure clo has an
 // empty list of captured vars.
 func IsTrivialClosure(clo *ClosureExpr) bool {
 	return len(clo.Func.ClosureVars) == 0
 }

 // globClosgen is like Func.Closgen, but for the global scope.
 var globClosgen int32

 // closureName generates a new unique name for a closure within outerfn.
 func closureName(outerfn *Func) *types.Sym {
 	pkg := types.LocalPkg
 	outer := "glob."
 	prefix := "func"
 	gen := &globClosgen

 	if outerfn != nil {
 		if outerfn.OClosure != nil {
 			prefix = ""
 		}

 		pkg = outerfn.Sym().Pkg
 		outer = FuncName(outerfn)

 		// There may be multiple functions named "_". In those
 		// cases, we can't use their individual Closgens as it
 		// would lead to name clashes.
 		if !IsBlank(outerfn.Nname) {
 			gen = &outerfn.Closgen
 		}
 	}

 	*gen++
 	return pkg.Lookup(fmt.Sprintf("%s.%s%d", outer, prefix, *gen))
 }

 // NewClosureFunc creates a new Func to represent a function literal.
 // If hidden is true, then the closure is marked hidden (i.e., as a
 // function literal contained within another function, rather than a
 // package-scope variable initialization expression).
 func NewClosureFunc(pos src.XPos, hidden bool) *Func {
 	fn := NewFunc(pos)
 	fn.SetIsHiddenClosure(hidden)

 	fn.Nname = NewNameAt(pos, BlankNode.Sym())
 	fn.Nname.Func = fn
 	fn.Nname.Defn = fn

 	fn.OClosure = NewClosureExpr(pos, fn)

 	return fn
 }

 // NameClosure generates a unique for the given function literal,
 // which must have appeared within outerfn.
 func NameClosure(clo *ClosureExpr, outerfn *Func) {
 	fn := clo.Func
 	if fn.IsHiddenClosure() != (outerfn != nil) {
 		base.FatalfAt(clo.Pos(), "closure naming inconsistency: hidden %v, but outer %v", fn.IsHiddenClosure(), outerfn)
 	}

 	name := fn.Nname
 	if !IsBlank(name) {
 		base.FatalfAt(clo.Pos(), "closure already named: %v", name)
 	}

 	name.SetSym(closureName(outerfn))
 	MarkFunc(name)
 }

 // UseClosure checks that the ginen function literal has been setup
 // correctly, and then returns it as an expression.
 // It must be called after clo.Func.ClosureVars has been set.
 func UseClosure(clo *ClosureExpr, pkg *Package) Node {
 	fn := clo.Func
 	name := fn.Nname

 	if IsBlank(name) {
 		base.FatalfAt(fn.Pos(), "unnamed closure func: %v", fn)
 	}
 	// Caution: clo.Typecheck() is still 0 when UseClosure is called by
 	// tcClosure.
 	if fn.Typecheck() != 1 || name.Typecheck() != 1 {
 		base.FatalfAt(fn.Pos(), "missed typecheck: %v", fn)
 	}
 	if clo.Type() == nil || name.Type() == nil {
 		base.FatalfAt(fn.Pos(), "missing types: %v", fn)
 	}
 	if !types.Identical(clo.Type(), name.Type()) {
 		base.FatalfAt(fn.Pos(), "mismatched types: %v", fn)
 	}

 	if base.Flag.W > 1 {
 		s := fmt.Sprintf("new closure func: %v", fn)
 		Dump(s, fn)
 	}

 	if pkg != nil {
 		pkg.Decls = append(pkg.Decls, fn)
 	}

 	if false && IsTrivialClosure(clo) {
 		// TODO(mdempsky): Investigate if we can/should optimize this
 		// case. walkClosure already handles it later, but it could be
 		// useful to recognize earlier (e.g., it might allow multiple
 		// inlined calls to a function to share a common trivial closure
 		// func, rather than cloning it for each inlined call).
 	}

 	return clo
 }
	// Copyright 2020 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 ir

	import (
	"cmd/compile/internal/base"
	"cmd/compile/internal/types"
	"cmd/internal/obj"
	"cmd/internal/src"
	"fmt"
	)

	// A Func corresponds to a single function in a Go program
	// (and vice versa: each function is denoted by exactly one *Func).
	//
	// There are multiple nodes that represent a Func in the IR.
	//
	// The ONAME node (Func.Nname) is used for plain references to it.
	// The ODCLFUNC node (the Func itself) is used for its declaration code.
	// The OCLOSURE node (Func.OClosure) is used for a reference to a
	// function literal.
	//
	// An imported function will have an ONAME node which points to a Func
	// with an empty body.
	// A declared function or method has an ODCLFUNC (the Func itself) and an ONAME.
	// A function literal is represented directly by an OCLOSURE, but it also
	// has an ODCLFUNC (and a matching ONAME) representing the compiled
	// underlying form of the closure, which accesses the captured variables
	// using a special data structure passed in a register.
	//
	// A method declaration is represented like functions, except f.Sym
	// will be the qualified method name (e.g., "T.m") and
	// f.Func.Shortname is the bare method name (e.g., "m").
	//
	// A method expression (T.M) is represented as an OMETHEXPR node,
	// in which n.Left and n.Right point to the type and method, respectively.
	// Each distinct mention of a method expression in the source code
	// constructs a fresh node.
	//
	// A method value (t.M) is represented by ODOTMETH/ODOTINTER
	// when it is called directly and by OMETHVALUE otherwise.
	// These are like method expressions, except that for ODOTMETH/ODOTINTER,
	// the method name is stored in Sym instead of Right.
	// Each OMETHVALUE ends up being implemented as a new
	// function, a bit like a closure, with its own ODCLFUNC.
	// The OMETHVALUE uses n.Func to record the linkage to
	// the generated ODCLFUNC, but there is no
	// pointer from the Func back to the OMETHVALUE.
	type Func struct {
	miniNode
	Body Nodes
	Iota int64

	Nname *Name // ONAME node
	OClosure *ClosureExpr // OCLOSURE node

	Shortname *types.Sym

	// Extra entry code for the function. For example, allocate and initialize
	// memory for escaping parameters.
	Enter Nodes
	Exit Nodes

	// ONAME nodes for all params/locals for this func/closure, does NOT
	// include closurevars until transforming closures during walk.
	// Names must be listed PPARAMs, PPARAMOUTs, then PAUTOs,
	// with PPARAMs and PPARAMOUTs in order corresponding to the function signature.
	// However, as anonymous or blank PPARAMs are not actually declared,
	// they are omitted from Dcl.
	// Anonymous and blank PPARAMOUTs are declared as ~rNN and ~bNN Names, respectively.
	Dcl []*Name

	// ClosureVars lists the free variables that are used within a
	// function literal, but formally declared in an enclosing
	// function. The variables in this slice are the closure function's
	// own copy of the variables, which are used within its function
	// body. They will also each have IsClosureVar set, and will have
	// Byval set if they're captured by value.
	ClosureVars []*Name

	// Enclosed functions that need to be compiled.
	// Populated during walk.
	Closures []*Func

	// Parents records the parent scope of each scope within a
	// function. The root scope (0) has no parent, so the i'th
	// scope's parent is stored at Parents[i-1].
	Parents []ScopeID

	// Marks records scope boundary changes.
	Marks []Mark

	FieldTrack map[*obj.LSym]struct{}
	DebugInfo interface{}
	LSym *obj.LSym // Linker object in this function's native ABI (Func.ABI)

	Inl *Inline

	// Closgen tracks how many closures have been generated within
	// this function. Used by closurename for creating unique
	// function names.
	Closgen int32

	Label int32 // largest auto-generated label in this function

	Endlineno src.XPos
	WBPos src.XPos // position of first write barrier; see SetWBPos

	Pragma PragmaFlag // go:xxx function annotations

	flags bitset16

	// ABI is a function's "definition" ABI. This is the ABI that
	// this function's generated code is expecting to be called by.
	//
	// For most functions, this will be obj.ABIInternal. It may be
	// a different ABI for functions defined in assembly or ABI wrappers.
	//
	// This is included in the export data and tracked across packages.
	ABI obj.ABI
	// ABIRefs is the set of ABIs by which this function is referenced.
	// For ABIs other than this function's definition ABI, the
	// compiler generates ABI wrapper functions. This is only tracked
	// within a package.
	ABIRefs obj.ABISet

	NumDefers int32 // number of defer calls in the function
	NumReturns int32 // number of explicit returns in the function

	// nwbrCalls records the LSyms of functions called by this
	// function for go:nowritebarrierrec analysis. Only filled in
	// if nowritebarrierrecCheck != nil.
	NWBRCalls *[]SymAndPos
	}

	func NewFunc(pos src.XPos) *Func {
	f := new(Func)
	f.pos = pos
	f.op = ODCLFUNC
	f.Iota = -1
	// Most functions are ABIInternal. The importer or symabis
	// pass may override this.
	f.ABI = obj.ABIInternal
	return f
	}

	func (f *Func) isStmt() {}

	func (n *Func) copy() Node { panic(n.no("copy")) }
	func (n *Func) doChildren(do func(Node) bool) bool { return doNodes(n.Body, do) }
	func (n *Func) editChildren(edit func(Node) Node) { editNodes(n.Body, edit) }

	func (f Func) Type() types.Type { return f.Nname.Type() }
	func (f Func) Sym() types.Sym { return f.Nname.Sym() }
	func (f Func) Linksym() obj.LSym { return f.Nname.Linksym() }
	func (f Func) LinksymABI(abi obj.ABI) obj.LSym { return f.Nname.LinksymABI(abi) }

	// 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 Func.Body for use during inlining. Copies are
	// needed because the function's dcl/body may be changed by later compiler
	// transformations. These fields are also populated when a function from
	// another package is imported.
	Dcl []*Name
	Body []Node

	// CanDelayResults reports whether it's safe for the inliner to delay
	// initializing the result parameters until immediately before the
	// "return" statement.
	CanDelayResults bool
	}

	// A Mark represents a scope boundary.
	type Mark struct {
	// Pos is the position of the token that marks the scope
	// change.
	Pos src.XPos

	// Scope identifies the innermost scope to the right of Pos.
	Scope ScopeID
	}

	// A ScopeID represents a lexical scope within a function.
	type ScopeID int32

	const (
	funcDupok = 1 << iota // duplicate definitions ok
	funcWrapper // hide frame from users (elide in tracebacks, don't count as a frame for recover())
	funcABIWrapper // is an ABI wrapper (also set flagWrapper)
	funcNeedctxt // function uses context register (has closure variables)
	funcReflectMethod // function calls reflect.Type.Method or MethodByName
	// true if closure inside a function; false if a simple function or a
	// closure in a global variable initialization
	funcIsHiddenClosure
	funcIsDeadcodeClosure // true if closure is deadcode
	funcHasDefer // contains a defer statement
	funcNilCheckDisabled // disable nil checks when compiling this function
	funcInlinabilityChecked // inliner has already determined whether the function is inlinable
	funcExportInline // include inline body in export data
	funcInstrumentBody // add race/msan/asan instrumentation during SSA construction
	funcOpenCodedDeferDisallowed // can't do open-coded defers
	funcClosureCalled // closure is only immediately called; used by escape analysis
	)

	type SymAndPos struct {
	Sym *obj.LSym // LSym of callee
	Pos src.XPos // line of call
	}

	func (f *Func) Dupok() bool { return f.flags&funcDupok != 0 }
	func (f *Func) Wrapper() bool { return f.flags&funcWrapper != 0 }
	func (f *Func) ABIWrapper() bool { return f.flags&funcABIWrapper != 0 }
	func (f *Func) Needctxt() bool { return f.flags&funcNeedctxt != 0 }
	func (f *Func) ReflectMethod() bool { return f.flags&funcReflectMethod != 0 }
	func (f *Func) IsHiddenClosure() bool { return f.flags&funcIsHiddenClosure != 0 }
	func (f *Func) IsDeadcodeClosure() bool { return f.flags&funcIsDeadcodeClosure != 0 }
	func (f *Func) HasDefer() bool { return f.flags&funcHasDefer != 0 }
	func (f *Func) NilCheckDisabled() bool { return f.flags&funcNilCheckDisabled != 0 }
	func (f *Func) InlinabilityChecked() bool { return f.flags&funcInlinabilityChecked != 0 }
	func (f *Func) ExportInline() bool { return f.flags&funcExportInline != 0 }
	func (f *Func) InstrumentBody() bool { return f.flags&funcInstrumentBody != 0 }
	func (f *Func) OpenCodedDeferDisallowed() bool { return f.flags&funcOpenCodedDeferDisallowed != 0 }
	func (f *Func) ClosureCalled() bool { return f.flags&funcClosureCalled != 0 }

	func (f *Func) SetDupok(b bool) { f.flags.set(funcDupok, b) }
	func (f *Func) SetWrapper(b bool) { f.flags.set(funcWrapper, b) }
	func (f *Func) SetABIWrapper(b bool) { f.flags.set(funcABIWrapper, b) }
	func (f *Func) SetNeedctxt(b bool) { f.flags.set(funcNeedctxt, b) }
	func (f *Func) SetReflectMethod(b bool) { f.flags.set(funcReflectMethod, b) }
	func (f *Func) SetIsHiddenClosure(b bool) { f.flags.set(funcIsHiddenClosure, b) }
	func (f *Func) SetIsDeadcodeClosure(b bool) { f.flags.set(funcIsDeadcodeClosure, b) }
	func (f *Func) SetHasDefer(b bool) { f.flags.set(funcHasDefer, b) }
	func (f *Func) SetNilCheckDisabled(b bool) { f.flags.set(funcNilCheckDisabled, b) }
	func (f *Func) SetInlinabilityChecked(b bool) { f.flags.set(funcInlinabilityChecked, b) }
	func (f *Func) SetExportInline(b bool) { f.flags.set(funcExportInline, b) }
	func (f *Func) SetInstrumentBody(b bool) { f.flags.set(funcInstrumentBody, b) }
	func (f *Func) SetOpenCodedDeferDisallowed(b bool) { f.flags.set(funcOpenCodedDeferDisallowed, b) }
	func (f *Func) SetClosureCalled(b bool) { f.flags.set(funcClosureCalled, b) }

	func (f *Func) SetWBPos(pos src.XPos) {
	if base.Debug.WB != 0 {
	base.WarnfAt(pos, "write barrier")
	}
	if !f.WBPos.IsKnown() {
	f.WBPos = pos
	}
	}

	// FuncName returns the name (without the package) of the function n.
	func FuncName(f *Func) string {
	if f == nil \|\| f.Nname == nil {
	return "<nil>"
	}
	return f.Sym().Name
	}

	// PkgFuncName returns the name of the function referenced by n, with package prepended.
	// This differs from the compiler's internal convention where local functions lack a package
	// because the ultimate consumer of this is a human looking at an IDE; package is only empty
	// if the compilation package is actually the empty string.
	func PkgFuncName(f *Func) string {
	if f == nil \|\| f.Nname == nil {
	return "<nil>"
	}
	s := f.Sym()
	pkg := s.Pkg

	p := base.Ctxt.Pkgpath
	if pkg != nil && pkg.Path != "" {
	p = pkg.Path
	}
	if p == "" {
	return s.Name
	}
	return p + "." + s.Name
	}

	var CurFunc *Func

	// WithFunc invokes do with CurFunc and base.Pos set to curfn and
	// curfn.Pos(), respectively, and then restores their previous values
	// before returning.
	func WithFunc(curfn *Func, do func()) {
	oldfn, oldpos := CurFunc, base.Pos
	defer func() { CurFunc, base.Pos = oldfn, oldpos }()

	CurFunc, base.Pos = curfn, curfn.Pos()
	do()
	}

	func FuncSymName(s *types.Sym) string {
	return s.Name + "·f"
	}

	// MarkFunc marks a node as a function.
	func MarkFunc(n *Name) {
	if n.Op() != ONAME \|\| n.Class != Pxxx {
	base.FatalfAt(n.Pos(), "expected ONAME/Pxxx node, got %v (%v/%v)", n, n.Op(), n.Class)
	}

	n.Class = PFUNC
	n.Sym().SetFunc(true)
	}

	// ClosureDebugRuntimeCheck applies boilerplate checks for debug flags
	// and compiling runtime
	func ClosureDebugRuntimeCheck(clo *ClosureExpr) {
	if base.Debug.Closure > 0 {
	if clo.Esc() == EscHeap {
	base.WarnfAt(clo.Pos(), "heap closure, captured vars = %v", clo.Func.ClosureVars)
	} else {
	base.WarnfAt(clo.Pos(), "stack closure, captured vars = %v", clo.Func.ClosureVars)
	}
	}
	if base.Flag.CompilingRuntime && clo.Esc() == EscHeap && !clo.IsGoWrap {
	base.ErrorfAt(clo.Pos(), "heap-allocated closure %s, not allowed in runtime", FuncName(clo.Func))
	}
	}

	// IsTrivialClosure reports whether closure clo has an
	// empty list of captured vars.
	func IsTrivialClosure(clo *ClosureExpr) bool {
	return len(clo.Func.ClosureVars) == 0
	}

	// globClosgen is like Func.Closgen, but for the global scope.
	var globClosgen int32

	// closureName generates a new unique name for a closure within outerfn.
	func closureName(outerfn Func) types.Sym {
	pkg := types.LocalPkg
	outer := "glob."
	prefix := "func"
	gen := &globClosgen

	if outerfn != nil {
	if outerfn.OClosure != nil {
	prefix = ""
	}

	pkg = outerfn.Sym().Pkg
	outer = FuncName(outerfn)

	// There may be multiple functions named "_". In those
	// cases, we can't use their individual Closgens as it
	// would lead to name clashes.
	if !IsBlank(outerfn.Nname) {
	gen = &outerfn.Closgen
	}
	}

	*gen++
	return pkg.Lookup(fmt.Sprintf("%s.%s%d", outer, prefix, *gen))
	}

	// NewClosureFunc creates a new Func to represent a function literal.
	// If hidden is true, then the closure is marked hidden (i.e., as a
	// function literal contained within another function, rather than a
	// package-scope variable initialization expression).
	func NewClosureFunc(pos src.XPos, hidden bool) *Func {
	fn := NewFunc(pos)
	fn.SetIsHiddenClosure(hidden)

	fn.Nname = NewNameAt(pos, BlankNode.Sym())
	fn.Nname.Func = fn
	fn.Nname.Defn = fn

	fn.OClosure = NewClosureExpr(pos, fn)

	return fn
	}

	// NameClosure generates a unique for the given function literal,
	// which must have appeared within outerfn.
	func NameClosure(clo ClosureExpr, outerfn Func) {
	fn := clo.Func
	if fn.IsHiddenClosure() != (outerfn != nil) {
	base.FatalfAt(clo.Pos(), "closure naming inconsistency: hidden %v, but outer %v", fn.IsHiddenClosure(), outerfn)
	}

	name := fn.Nname
	if !IsBlank(name) {
	base.FatalfAt(clo.Pos(), "closure already named: %v", name)
	}

	name.SetSym(closureName(outerfn))
	MarkFunc(name)
	}

	// UseClosure checks that the ginen function literal has been setup
	// correctly, and then returns it as an expression.
	// It must be called after clo.Func.ClosureVars has been set.
	func UseClosure(clo ClosureExpr, pkg Package) Node {
	fn := clo.Func
	name := fn.Nname

	if IsBlank(name) {
	base.FatalfAt(fn.Pos(), "unnamed closure func: %v", fn)
	}
	// Caution: clo.Typecheck() is still 0 when UseClosure is called by
	// tcClosure.
	if fn.Typecheck() != 1 \|\| name.Typecheck() != 1 {
	base.FatalfAt(fn.Pos(), "missed typecheck: %v", fn)
	}
	if clo.Type() == nil \|\| name.Type() == nil {
	base.FatalfAt(fn.Pos(), "missing types: %v", fn)
	}
	if !types.Identical(clo.Type(), name.Type()) {
	base.FatalfAt(fn.Pos(), "mismatched types: %v", fn)
	}

	if base.Flag.W > 1 {
	s := fmt.Sprintf("new closure func: %v", fn)
	Dump(s, fn)
	}

	if pkg != nil {
	pkg.Decls = append(pkg.Decls, fn)
	}

	if false && IsTrivialClosure(clo) {
	// TODO(mdempsky): Investigate if we can/should optimize this
	// case. walkClosure already handles it later, but it could be
	// useful to recognize earlier (e.g., it might allow multiple
	// inlined calls to a function to share a common trivial closure
	// func, rather than cloning it for each inlined call).
	}

	return clo
	}