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// 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 (
// 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").
// 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 {
Body Nodes
Nname *Name // ONAME node
OClosure *ClosureExpr // OCLOSURE node
// 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.
// 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
// For wrapper functions, WrappedFunc point to the original Func.
// Currently only used for go/defer wrappers.
WrappedFunc *Func
func NewFunc(pos src.XPos) *Func {
f := new(Func)
f.pos = pos
// 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("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 (n *Func) editChildrenWithHidden(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
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
return pkg.Path + "." + 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()
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
// 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
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.Nname = NewNameAt(pos, BlankNode.Sym())
fn.Nname.Func = fn
fn.Nname.Defn = fn
fn.OClosure = &ClosureExpr{Func: fn}
fn.OClosure.op = OCLOSURE
fn.OClosure.pos = pos
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)
// 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