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949 lines (860 loc) · 26.4 KB
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// Copyright 2013 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
// This file implements the Function type.
import (
"bytes"
"fmt"
"go/ast"
"go/token"
"go/types"
"io"
"iter"
"os"
"strings"
)
// Like ObjectOf, but panics instead of returning nil.
// Only valid during f's create and build phases.
func (f *Function) objectOf(id *ast.Ident) types.Object {
if o := f.info.ObjectOf(id); o != nil {
return o
}
panic(fmt.Sprintf("no types.Object for ast.Ident %s @ %s",
id.Name, f.Prog.Fset.Position(id.Pos())))
}
// instrs returns an iterator that returns each reachable instruction of the SSA function.
func (f *Function) instrs() iter.Seq[Instruction] {
return func(yield func(i Instruction) bool) {
for _, block := range f.Blocks {
for _, instr := range block.Instrs {
if !yield(instr) {
return
}
}
}
}
}
// Like TypeOf, but panics instead of returning nil.
// Only valid during f's create and build phases.
func (f *Function) typeOf(e ast.Expr) types.Type {
if T := f.info.TypeOf(e); T != nil {
return f.typ(T)
}
panic(fmt.Sprintf("no type for %T @ %s", e, f.Prog.Fset.Position(e.Pos())))
}
// typ is the locally instantiated type of T.
// If f is not an instantiation, then f.typ(T)==T.
func (f *Function) typ(T types.Type) types.Type {
return f.subst.typ(T)
}
// If id is an Instance, returns info.Instances[id].Type.
// Otherwise returns f.typeOf(id).
func (f *Function) instanceType(id *ast.Ident) types.Type {
if t, ok := f.info.Instances[id]; ok {
return t.Type
}
return f.typeOf(id)
}
// selection returns a *selection corresponding to f.info.Selections[selector]
// with potential updates for type substitution.
func (f *Function) selection(selector *ast.SelectorExpr) *selection {
sel := f.info.Selections[selector]
if sel == nil {
return nil
}
switch sel.Kind() {
case types.MethodExpr, types.MethodVal:
if recv := f.typ(sel.Recv()); recv != sel.Recv() {
// recv changed during type substitution.
pkg := f.declaredPackage().Pkg
obj, index, indirect := types.LookupFieldOrMethod(recv, true, pkg, sel.Obj().Name())
// sig replaces sel.Type(). See (types.Selection).Typ() for details.
sig := obj.Type().(*types.Signature)
sig = changeRecv(sig, newVar(sig.Recv().Name(), recv))
if sel.Kind() == types.MethodExpr {
sig = recvAsFirstArg(sig)
}
return &selection{
kind: sel.Kind(),
recv: recv,
typ: sig,
obj: obj,
index: index,
indirect: indirect,
}
}
}
return toSelection(sel)
}
// Destinations associated with unlabelled for/switch/select stmts.
// We push/pop one of these as we enter/leave each construct and for
// each BranchStmt we scan for the innermost target of the right type.
type targets struct {
tail *targets // rest of stack
_break *BasicBlock
_continue *BasicBlock
_fallthrough *BasicBlock
}
// Destinations associated with a labelled block.
// We populate these as labels are encountered in forward gotos or
// labelled statements.
// Forward gotos are resolved once it is known which statement they
// are associated with inside the Function.
type lblock struct {
label *types.Label // Label targeted by the blocks.
resolved bool // _goto block encountered (back jump or resolved fwd jump)
_goto *BasicBlock
_break *BasicBlock
_continue *BasicBlock
}
// label returns the symbol denoted by a label identifier.
//
// label should be a non-blank identifier (label.Name != "_").
func (f *Function) label(label *ast.Ident) *types.Label {
return f.objectOf(label).(*types.Label)
}
// lblockOf returns the branch target associated with the
// specified label, creating it if needed.
func (f *Function) lblockOf(label *types.Label) *lblock {
lb := f.lblocks[label]
if lb == nil {
lb = &lblock{
label: label,
_goto: f.newBasicBlock(label.Name()),
}
if f.lblocks == nil {
f.lblocks = make(map[*types.Label]*lblock)
}
f.lblocks[label] = lb
}
return lb
}
// labelledBlock searches f for the block of the specified label.
//
// If f is a yield function, it additionally searches ancestor Functions
// corresponding to enclosing range-over-func statements within the
// same source function, so the returned block may belong to a different Function.
func labelledBlock(f *Function, label *types.Label, tok token.Token) *BasicBlock {
if lb := f.lblocks[label]; lb != nil {
var block *BasicBlock
switch tok {
case token.BREAK:
block = lb._break
case token.CONTINUE:
block = lb._continue
case token.GOTO:
block = lb._goto
}
if block != nil {
return block
}
}
// Search ancestors if this is a yield function.
if f.jump != nil {
return labelledBlock(f.parent, label, tok)
}
return nil
}
// targetedBlock looks for the nearest block in f.targets
// (and f's ancestors) that matches tok's type, and returns
// the block and function it was found in.
func targetedBlock(f *Function, tok token.Token) *BasicBlock {
if f == nil {
return nil
}
for t := f.targets; t != nil; t = t.tail {
var block *BasicBlock
switch tok {
case token.BREAK:
block = t._break
case token.CONTINUE:
block = t._continue
case token.FALLTHROUGH:
block = t._fallthrough
}
if block != nil {
return block
}
}
// Search f's ancestors (in case f is a yield function).
return targetedBlock(f.parent, tok)
}
// addResultVar adds a result for a variable v to f.results and v to f.returnVars.
func (f *Function) addResultVar(v *types.Var, source ast.Node) {
name := v.Name()
if name == "" {
name = fmt.Sprintf("res.%d", len(f.results))
}
result := emitLocalVar(f, v, source)
result.comment = name
f.results = append(f.results, result)
f.returnVars = append(f.returnVars, v)
}
// addParamVar adds a parameter to f.Params.
func (f *Function) addParamVar(v *types.Var, source ast.Node) *Parameter {
name := v.Name()
if name == "" {
name = fmt.Sprintf("arg%d", len(f.Params))
}
param := &Parameter{name: name, typ: f.typ(v.Type()), parent: f}
param.setSource(source)
param.object = v
f.Params = append(f.Params, param)
return param
}
// addSpilledParam declares a parameter that is pre-spilled to the
// stack; the function body will load/store the spilled location.
// Subsequent lifting will eliminate spills where possible.
func (f *Function) addSpilledParam(obj *types.Var, source ast.Node) {
param := f.addParamVar(obj, source)
spill := emitLocalVar(f, obj, source)
emitStore(f, spill, param, source)
}
// startBody initializes the function prior to generating IR code for its body.
// Precondition: f.Type() already set.
func (f *Function) startBody() {
entry := f.newBasicBlock("entry")
f.currentBlock = entry
f.vars = make(map[*types.Var]Value) // needed for some synthetics, e.g. init
}
func (f *Function) blockset(i int) *BlockSet {
bs := &f.blocksets[i]
if len(bs.values) != len(f.Blocks) {
if cap(bs.values) >= len(f.Blocks) {
bs.values = bs.values[:len(f.Blocks)]
bs.Clear()
} else {
bs.values = make([]bool, len(f.Blocks))
}
} else {
bs.Clear()
}
return bs
}
// createSyntacticParams populates f.Params and generates code (spills
// and named result locals) for all the parameters declared in the
// syntax. In addition it populates the f.objects mapping.
//
// Preconditions:
// f.startBody() was called. f.info != nil.
// Postcondition:
// len(f.Params) == len(f.Signature.Params) + (f.Signature.Recv() ? 1 : 0)
func (f *Function) createSyntacticParams(recv *ast.FieldList, functype *ast.FuncType) {
// Receiver (at most one inner iteration).
if recv != nil {
for _, field := range recv.List {
for _, n := range field.Names {
f.addSpilledParam(identVar(f, n), n)
}
// Anonymous receiver? No need to spill.
if field.Names == nil {
f.addParamVar(f.Signature.Recv(), field)
}
}
}
// Parameters.
if functype.Params != nil {
n := len(f.Params) // 1 if has recv, 0 otherwise
for _, field := range functype.Params.List {
for _, n := range field.Names {
f.addSpilledParam(identVar(f, n), n)
}
// Anonymous parameter? No need to spill.
if field.Names == nil {
f.addParamVar(f.Signature.Params().At(len(f.Params)-n), field)
}
}
}
// Results.
if functype.Results != nil {
for _, field := range functype.Results.List {
// Implicit "var" decl of locals for named results.
for _, n := range field.Names {
v := identVar(f, n)
f.addResultVar(v, n)
}
// Implicit "var" decl of local for an unnamed result.
if field.Names == nil {
v := f.Signature.Results().At(len(f.results))
f.addResultVar(v, field.Type)
}
}
}
}
// createDeferStack initializes fn.deferstack to a local variable
// initialized to a ssa:deferstack() call.
func (fn *Function) createDeferStack() {
// Each syntactic function makes a call to ssa:deferstack,
// which is spilled to a local. Unused ones are later removed.
fn.deferstack = newVar("defer$stack", tDeferStack)
call := &Call{Call: CallCommon{Value: vDeferStack}}
call.setType(tDeferStack)
deferstack := fn.emit(call, nil)
spill := emitLocalVar(fn, fn.deferstack, nil)
emitStore(fn, spill, deferstack, nil)
}
func numberNodes(f *Function) {
var base ID
for _, b := range f.Blocks {
for _, instr := range b.Instrs {
if instr == nil {
continue
}
base++
instr.setID(base)
}
}
}
func updateOperandsReferrers(instr Instruction, ops []*Value) {
for _, op := range ops {
if r := *op; r != nil {
if refs := (*op).Referrers(); refs != nil {
if len(*refs) == 0 {
// per median, each value has two referrers, so we can avoid one call into growslice
//
// Note: we experimented with allocating
// sequential scratch space, but we
// couldn't find a value that gave better
// performance than making many individual
// allocations
*refs = make([]Instruction, 1, 2)
(*refs)[0] = instr
} else {
*refs = append(*refs, instr)
}
}
}
}
}
// buildReferrers populates the def/use information in all non-nil
// Value.Referrers slice.
// Precondition: all such slices are initially empty.
func buildReferrers(f *Function) {
var rands []*Value
for _, b := range f.Blocks {
for _, instr := range b.Instrs {
rands = instr.Operands(rands[:0]) // recycle storage
updateOperandsReferrers(instr, rands)
}
}
}
// finishBody() finalizes the contents of the function after IR code generation of its body.
//
// The function is not done being built until done() is called.
func (f *Function) finishBody() {
f.currentBlock = nil
f.lblocks = nil
f.returnVars = nil
f.jump = nil
f.source = nil
f.exits = nil
// Remove from f.Locals any Allocs that escape to the heap.
j := 0
for _, l := range f.Locals {
if !l.Heap {
f.Locals[j] = l
j++
}
}
// Nil out f.Locals[j:] to aid GC.
for i := j; i < len(f.Locals); i++ {
f.Locals[i] = nil
}
f.Locals = f.Locals[:j]
optimizeBlocks(f)
buildReferrers(f)
buildDomTree(f)
buildSCCs(f)
if f.Prog.mode&NaiveForm == 0 {
for lift(f) {
}
if doSimplifyConstantCompositeValues {
for simplifyConstantCompositeValues(f) {
}
}
}
if f.debugInfo() {
// Turn debug references into a map
f.exprToValue = map[ast.Expr]struct {
v Value
isAddr bool
}{}
for _, b := range f.Blocks {
newInstrs := b.Instrs[:0]
for _, instr := range b.Instrs {
if instr, ok := instr.(*debugRef); ok {
if refs := instr.X.Referrers(); refs != nil {
*refs = removeInstr(*refs, instr)
}
if _, ok := f.exprToValue[instr.Expr]; !ok {
f.exprToValue[instr.Expr] = struct {
v Value
isAddr bool
}{instr.X, instr.IsAddr}
}
continue
}
newInstrs = append(newInstrs, instr)
}
b.Instrs = newInstrs
}
}
// clear remaining builder state
f.results = nil // (used by lifting)
f.deferstack = nil // (used by lifting)
f.vars = nil // (used by lifting)
numberNodes(f)
// clear out other function state (keep consistent with buildParamsOnly)
f.subst = nil
// Release the package's type information, unless
// instances of f will later be built from it.
if !f.isGenericOrigin() {
f.info = nil
}
numberNodes(f)
}
// done marks the building of f's SSA body complete,
// along with any nested functions, and optionally prints them.
func (f *Function) done() {
assert(f.parent == nil, "done called on an anonymous function")
var visit func(*Function)
visit = func(f *Function) {
for _, anon := range f.AnonFuncs {
visit(anon) // anon is done building before f.
}
f.uniq = 0 // done with uniq
f.build = nil // function is built
if f.Prog.mode&PrintFunctions != 0 {
printMu.Lock()
f.WriteTo(os.Stdout)
printMu.Unlock()
}
if f.Prog.mode&SanityCheckFunctions != 0 {
mustSanityCheck(f, nil)
}
}
visit(f)
}
func isUselessPhi(phi *Phi) (Value, bool) {
var v0 Value
if len(phi.Edges) == 0 {
panic("φ with no edges")
}
for _, e := range phi.Edges {
if e == nil {
panic(fmt.Sprintf("φ has nil edge: %v", phi))
}
if e == phi {
continue
}
if v0 == nil {
v0 = e
}
if v0 != e {
if v0, ok := v0.(*Const); ok {
if e, ok := e.(*Const); ok {
if v0.typ == e.typ && v0.Value == e.Value {
continue
}
}
}
return nil, false
}
}
if v0 == nil {
panic("trying to replace φ with nil")
}
return v0, true
}
// removeNilBlocks eliminates nils from f.Blocks and updates each
// BasicBlock.Index. Use this after any pass that may delete blocks.
func (f *Function) removeNilBlocks() {
j := 0
for _, b := range f.Blocks {
if b != nil {
b.Index = j
f.Blocks[j] = b
j++
}
}
// Nil out f.Blocks[j:] to aid GC.
for i := j; i < len(f.Blocks); i++ {
f.Blocks[i] = nil
}
f.Blocks = f.Blocks[:j]
}
// SetDebugMode sets the debug mode for package pkg. If true, all its
// functions will include full debug info. This greatly increases the
// size of the instruction stream, and causes Functions to depend upon
// the ASTs, potentially keeping them live in memory for longer.
func (pkg *Package) SetDebugMode(debug bool) {
pkg.debug = debug
}
// debugInfo reports whether debug info is wanted for this function.
func (f *Function) debugInfo() bool {
// debug info for instantiations follows the debug info of their origin.
p := f.declaredPackage()
return p != nil && p.debug
}
// lookup returns the address of the named variable identified by obj
// that is local to function f or one of its enclosing functions.
// If escaping, the reference comes from a potentially escaping pointer
// expression and the referent must be heap-allocated.
// We assume the referent is a *Alloc or *Phi.
// (The only Phis at this stage are those created directly by go1.22 "for" loops.)
func (f *Function) lookup(obj *types.Var, escaping bool) Value {
if v, ok := f.vars[obj]; ok {
if escaping {
switch v := v.(type) {
case *Alloc:
v.Heap = true
case *Phi:
for _, edge := range v.Edges {
if alloc, ok := edge.(*Alloc); ok {
alloc.Heap = true
}
}
}
}
return v // function-local var (address)
}
// Definition must be in an enclosing function;
// plumb it through intervening closures.
if f.parent == nil {
panic("no ir.Value for " + obj.String())
}
outer := f.parent.lookup(obj, true) // escaping
v := &FreeVar{
name: obj.Name(),
typ: outer.Type(),
outer: outer,
parent: f,
}
f.vars[obj] = v
f.FreeVars = append(f.FreeVars, v)
return v
}
// emit emits the specified instruction to function f.
func (f *Function) emit(instr Instruction, source ast.Node) Value {
return f.currentBlock.emit(instr, source)
}
// RelString returns the full name of this function, qualified by
// package name, receiver type, etc.
//
// The specific formatting rules are not guaranteed and may change.
//
// Examples:
//
// "math.IsNaN" // a package-level function
// "(*bytes.Buffer).Bytes" // a declared method or a wrapper
// "(*bytes.Buffer).Bytes$thunk" // thunk (func wrapping method; receiver is param 0)
// "(*bytes.Buffer).Bytes$bound" // bound (func wrapping method; receiver supplied by closure)
// "main.main$1" // an anonymous function in main
// "main.init#1" // a declared init function
// "main.init" // the synthesized package initializer
//
// When these functions are referred to from within the same package
// (i.e. from == f.Pkg.Object), they are rendered without the package path.
// For example: "IsNaN", "(*Buffer).Bytes", etc.
//
// All non-synthetic functions have distinct package-qualified names.
// (But two methods may have the same name "(T).f" if one is a synthetic
// wrapper promoting a non-exported method "f" from another package; in
// that case, the strings are equal but the identifiers "f" are distinct.)
func (f *Function) RelString(from *types.Package) string {
// Anonymous?
if f.parent != nil {
// An anonymous function's Name() looks like "parentName$1",
// but its String() should include the type/package/etc.
parent := f.parent.RelString(from)
for i, anon := range f.parent.AnonFuncs {
if anon == f {
return fmt.Sprintf("%s$%d", parent, 1+i)
}
}
return f.name // should never happen
}
// Method (declared or wrapper)?
if recv := f.Signature.Recv(); recv != nil {
return f.relMethod(from, recv.Type())
}
// Thunk?
if f.method != nil {
return f.relMethod(from, f.method.recv)
}
// Bound?
if len(f.FreeVars) == 1 && strings.HasSuffix(f.name, "$bound") {
return f.relMethod(from, f.FreeVars[0].Type())
}
// Package-level function?
// Prefix with package name for cross-package references only.
if p := f.relPkg(); p != nil && p != from {
return fmt.Sprintf("%s.%s", p.Path(), f.name)
}
// Unknown.
return f.name
}
func (f *Function) relMethod(from *types.Package, recv types.Type) string {
return fmt.Sprintf("(%s).%s", relType(recv, from), f.name)
}
// writeSignature writes to buf the signature sig in declaration syntax.
func writeSignature(buf *bytes.Buffer, from *types.Package, name string, sig *types.Signature) {
buf.WriteString("func ")
if recv := sig.Recv(); recv != nil {
buf.WriteString("(")
if name := recv.Name(); name != "" {
buf.WriteString(name)
buf.WriteString(" ")
}
types.WriteType(buf, recv.Type(), types.RelativeTo(from))
buf.WriteString(") ")
}
buf.WriteString(name)
types.WriteSignature(buf, sig, types.RelativeTo(from))
}
// declaredPackage returns the package fn is declared in or nil if the
// function is not declared in a package.
func (fn *Function) declaredPackage() *Package {
switch {
case fn.Pkg != nil:
return fn.Pkg // non-generic function (does that follow??)
case fn.topLevelOrigin != nil:
return fn.topLevelOrigin.Pkg // instance of a named generic function
case fn.parent != nil:
return fn.parent.declaredPackage() // instance of an anonymous [generic] function
default:
return nil // function is not declared in a package, e.g. a wrapper.
}
}
// relPkg returns types.Package fn is printed in relationship to.
func (fn *Function) relPkg() *types.Package {
if p := fn.declaredPackage(); p != nil {
return p.Pkg
}
return nil
}
var _ io.WriterTo = (*Function)(nil) // *Function implements io.Writer
func (f *Function) WriteTo(w io.Writer) (int64, error) {
var buf bytes.Buffer
WriteFunction(&buf, f)
n, err := w.Write(buf.Bytes())
return int64(n), err
}
// WriteFunction writes to buf a human-readable "disassembly" of f.
func WriteFunction(buf *bytes.Buffer, f *Function) {
fmt.Fprintf(buf, "# Name: %s\n", f.String())
if f.Pkg != nil {
fmt.Fprintf(buf, "# Package: %s\n", f.Pkg.Pkg.Path())
}
if syn := f.Synthetic; syn != "" {
fmt.Fprintln(buf, "# Synthetic:", syn)
}
if pos := f.Pos(); pos.IsValid() {
fmt.Fprintf(buf, "# Location: %s\n", f.Prog.Fset.Position(pos))
}
if f.parent != nil {
fmt.Fprintf(buf, "# Parent: %s\n", f.parent.Name())
}
from := f.relPkg()
// NB. column calculations are confused by non-ASCII
// characters
const punchcard = 80 // for old time's sake.
const padding = " "
if f.FreeVars != nil {
buf.WriteString("# Free variables:\n")
for i, fv := range f.FreeVars {
fmt.Fprintf(buf, "# % 3d:%s%s %s\n", i, padding, fv.Name(), relType(fv.Type(), from))
}
}
if len(f.Locals) > 0 {
buf.WriteString("# Locals:\n")
for i, l := range f.Locals {
fmt.Fprintf(buf, "# % 3d:%s%s %s\n", i, padding, l.Name(), relType(deref(l.Type()), from))
}
}
writeSignature(buf, from, f.Name(), f.Signature)
buf.WriteString(":\n")
if f.Blocks == nil {
buf.WriteString(padding)
buf.WriteString("(external)\n")
}
for _, b := range f.Blocks {
if b == nil {
// Corrupt CFG.
fmt.Fprintf(buf, ".nil:\n")
continue
}
n, _ := fmt.Fprintf(buf, "%d:", b.Index)
// (|predecessors|, |successors|, immediate dominator)
bmsg := fmt.Sprintf("%s P:%d S:%d", b.Comment, len(b.Preds), len(b.Succs))
if b.Idom() != nil {
bmsg = fmt.Sprintf("%s idom:%d", bmsg, b.Idom().Index)
}
fmt.Fprintf(buf, "%*s%s\n", punchcard-1-n-len(bmsg), "", bmsg)
if false { // CFG debugging
fmt.Fprintf(buf, "%s# CFG: %s --> %s --> %s\n", padding, b.Preds, b, b.Succs)
}
for _, instr := range b.Instrs {
buf.WriteString(padding)
switch v := instr.(type) {
case Value:
l := punchcard - len(padding)
// Left-align the instruction.
if name := v.Name(); name != "" {
n, _ := fmt.Fprintf(buf, "%s = ", name)
l -= n
}
n, _ := buf.WriteString(instr.String())
l -= n
// Right-align the type if there's space.
if t := v.Type(); t != nil {
buf.WriteByte(' ')
ts := relType(t, from)
l -= len(ts) + len(" ") // (spaces before and after type)
if l > 0 {
fmt.Fprintf(buf, "%*s", l, "")
}
buf.WriteString(ts)
}
case nil:
// Be robust against bad transforms.
buf.WriteString("<deleted>")
default:
buf.WriteString(instr.String())
}
// -mode=S: show line numbers
if f.Prog.mode&LogSource != 0 {
if pos := instr.Pos(); pos.IsValid() {
fmt.Fprintf(buf, " L%d", f.Prog.Fset.Position(pos).Line)
}
}
buf.WriteString("\n")
}
}
buf.WriteString("\n")
}
// newBasicBlock adds to f a new basic block and returns it. It does
// not automatically become the current block for subsequent calls to emit.
// comment is an optional string for more readable debugging output.
func (f *Function) newBasicBlock(comment string) *BasicBlock {
b := &BasicBlock{
Index: len(f.Blocks),
Comment: comment,
parent: f,
}
b.Succs = b.succs2[:0]
f.Blocks = append(f.Blocks, b)
return b
}
// NewFunction returns a new synthetic Function instance belonging to
// prog, with its name and signature fields set as specified.
//
// The caller is responsible for initializing the remaining fields of
// the function object, e.g. Pkg, Params, Blocks.
//
// It is practically impossible for clients to construct well-formed
// IR functions/packages/programs directly, so we assume this is the
// job of the Builder alone. NewFunction exists to provide clients a
// little flexibility. For example, analysis tools may wish to
// construct fake Functions for the root of the callgraph, a fake
// "reflect" package, etc.
//
// TODO(adonovan): think harder about the API here.
func (prog *Program) NewFunction(name string, sig *types.Signature, provenance string) *Function {
return &Function{Prog: prog, name: name, Signature: sig, Synthetic: provenance}
}
//lint:ignore U1000 we may make use of this for functions loaded from export data
type extentNode [2]token.Pos
func (n extentNode) Pos() token.Pos { return n[0] }
func (n extentNode) End() token.Pos { return n[1] }
func killInstruction(instr Instruction) {
ops := instr.Operands(nil)
for _, op := range ops {
if refs := (*op).Referrers(); refs != nil {
*refs = removeInstr(*refs, instr)
}
}
}
// Syntax returns the function's syntax (*ast.Func{Decl,Lit})
// if it was produced from syntax or an *ast.RangeStmt if
// it is a range-over-func yield function.
func (f *Function) Syntax() ast.Node { return f.syntax }
// identVar returns the variable defined by id.
func identVar(fn *Function, id *ast.Ident) *types.Var {
return fn.info.Defs[id].(*types.Var)
}
// unique returns a unique positive int within the source tree of f.
// The source tree of f includes all of f's ancestors by parent and all
// of the AnonFuncs contained within these.
func unique(f *Function) int64 {
f.uniq++
return f.uniq
}
// exit is a change of control flow going from a range-over-func
// yield function to an ancestor function caused by a break, continue,
// goto, or return statement.
//
// There are 3 types of exits:
// * return from the source function (from ReturnStmt),
// * jump to a block (from break and continue statements [labelled/unlabelled]),
// * go to a label (from goto statements).
//
// As the builder does one pass over the ast, it is unclear whether
// a forward goto statement will leave a range-over-func body.
// The function being exited to is unresolved until the end
// of building the range-over-func body.
type exit struct {
id int64 // unique value for exit within from and to
from *Function // the function the exit starts from
to *Function // the function being exited to (nil if unresolved)
source ast.Node
block *BasicBlock // basic block within to being jumped to.
label *types.Label // forward label being jumped to via goto.
// block == nil && label == nil => return
}
// storeVar emits to function f code to store a value v to a *types.Var x.
func storeVar(f *Function, x *types.Var, v Value, source ast.Node) {
emitStore(f, f.lookup(x, true), v, source)
}
// labelExit creates a new exit to a yield fn to exit the function using a label.
func labelExit(fn *Function, label *types.Label, source ast.Node) *exit {
e := &exit{
id: unique(fn),
from: fn,
to: nil,
source: source,
label: label,
}
fn.exits = append(fn.exits, e)
return e
}
// blockExit creates a new exit to a yield fn that jumps to a basic block.
func blockExit(fn *Function, block *BasicBlock, source ast.Node) *exit {
e := &exit{
id: unique(fn),
from: fn,
to: block.parent,
source: source,
block: block,
}
fn.exits = append(fn.exits, e)
return e
}
// returnExit creates a new exit to a yield fn that returns to the source function.
func returnExit(fn *Function, source ast.Node) *exit {
e := &exit{
id: unique(fn),
from: fn,
to: fn.source,
source: source,
}
fn.exits = append(fn.exits, e)
return e
}
// isGenericOrigin reports whether f is an uninstantiated generic
// function or a method of an uninstantiated generic type.
func (f *Function) isGenericOrigin() bool {
return (f.typeparams.Len() > 0 && len(f.typeargs) == 0) ||
(f.recvtypeparams.Len() > 0 && len(f.recvtypeargs) == 0)
}