+++ /dev/null
-// 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 ssa
-
-// This file implements the Function and BasicBlock types.
-
-import (
- "bytes"
- "fmt"
- "go/ast"
- "go/token"
- "go/types"
- "io"
- "os"
- "strings"
-)
-
-// addEdge adds a control-flow graph edge from from to to.
-func addEdge(from, to *BasicBlock) {
- from.Succs = append(from.Succs, to)
- to.Preds = append(to.Preds, from)
-}
-
-// Parent returns the function that contains block b.
-func (b *BasicBlock) Parent() *Function { return b.parent }
-
-// String returns a human-readable label of this block.
-// It is not guaranteed unique within the function.
-//
-func (b *BasicBlock) String() string {
- return fmt.Sprintf("%d", b.Index)
-}
-
-// emit appends an instruction to the current basic block.
-// If the instruction defines a Value, it is returned.
-//
-func (b *BasicBlock) emit(i Instruction) Value {
- i.setBlock(b)
- b.Instrs = append(b.Instrs, i)
- v, _ := i.(Value)
- return v
-}
-
-// predIndex returns the i such that b.Preds[i] == c or panics if
-// there is none.
-func (b *BasicBlock) predIndex(c *BasicBlock) int {
- for i, pred := range b.Preds {
- if pred == c {
- return i
- }
- }
- panic(fmt.Sprintf("no edge %s -> %s", c, b))
-}
-
-// hasPhi returns true if b.Instrs contains φ-nodes.
-func (b *BasicBlock) hasPhi() bool {
- _, ok := b.Instrs[0].(*Phi)
- return ok
-}
-
-// phis returns the prefix of b.Instrs containing all the block's φ-nodes.
-func (b *BasicBlock) phis() []Instruction {
- for i, instr := range b.Instrs {
- if _, ok := instr.(*Phi); !ok {
- return b.Instrs[:i]
- }
- }
- return nil // unreachable in well-formed blocks
-}
-
-// replacePred replaces all occurrences of p in b's predecessor list with q.
-// Ordinarily there should be at most one.
-//
-func (b *BasicBlock) replacePred(p, q *BasicBlock) {
- for i, pred := range b.Preds {
- if pred == p {
- b.Preds[i] = q
- }
- }
-}
-
-// replaceSucc replaces all occurrences of p in b's successor list with q.
-// Ordinarily there should be at most one.
-//
-func (b *BasicBlock) replaceSucc(p, q *BasicBlock) {
- for i, succ := range b.Succs {
- if succ == p {
- b.Succs[i] = q
- }
- }
-}
-
-// removePred removes all occurrences of p in b's
-// predecessor list and φ-nodes.
-// Ordinarily there should be at most one.
-//
-func (b *BasicBlock) removePred(p *BasicBlock) {
- phis := b.phis()
-
- // We must preserve edge order for φ-nodes.
- j := 0
- for i, pred := range b.Preds {
- if pred != p {
- b.Preds[j] = b.Preds[i]
- // Strike out φ-edge too.
- for _, instr := range phis {
- phi := instr.(*Phi)
- phi.Edges[j] = phi.Edges[i]
- }
- j++
- }
- }
- // Nil out b.Preds[j:] and φ-edges[j:] to aid GC.
- for i := j; i < len(b.Preds); i++ {
- b.Preds[i] = nil
- for _, instr := range phis {
- instr.(*Phi).Edges[i] = nil
- }
- }
- b.Preds = b.Preds[:j]
- for _, instr := range phis {
- phi := instr.(*Phi)
- phi.Edges = phi.Edges[:j]
- }
-}
-
-// 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.
-//
-type lblock struct {
- _goto *BasicBlock
- _break *BasicBlock
- _continue *BasicBlock
-}
-
-// labelledBlock returns the branch target associated with the
-// specified label, creating it if needed.
-//
-func (f *Function) labelledBlock(label *ast.Ident) *lblock {
- lb := f.lblocks[label.Obj]
- if lb == nil {
- lb = &lblock{_goto: f.newBasicBlock(label.Name)}
- if f.lblocks == nil {
- f.lblocks = make(map[*ast.Object]*lblock)
- }
- f.lblocks[label.Obj] = lb
- }
- return lb
-}
-
-// addParam adds a (non-escaping) parameter to f.Params of the
-// specified name, type and source position.
-//
-func (f *Function) addParam(name string, typ types.Type, pos token.Pos) *Parameter {
- v := &Parameter{
- name: name,
- typ: typ,
- pos: pos,
- parent: f,
- }
- f.Params = append(f.Params, v)
- return v
-}
-
-func (f *Function) addParamObj(obj types.Object) *Parameter {
- name := obj.Name()
- if name == "" {
- name = fmt.Sprintf("arg%d", len(f.Params))
- }
- param := f.addParam(name, obj.Type(), obj.Pos())
- param.object = obj
- 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.Object) {
- param := f.addParamObj(obj)
- spill := &Alloc{Comment: obj.Name()}
- spill.setType(types.NewPointer(obj.Type()))
- spill.setPos(obj.Pos())
- f.objects[obj] = spill
- f.Locals = append(f.Locals, spill)
- f.emit(spill)
- f.emit(&Store{Addr: spill, Val: param})
-}
-
-// startBody initializes the function prior to generating SSA code for its body.
-// Precondition: f.Type() already set.
-//
-func (f *Function) startBody() {
- f.currentBlock = f.newBasicBlock("entry")
- f.objects = make(map[types.Object]Value) // needed for some synthetics, e.g. init
-}
-
-// 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.
-// 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(f.Pkg.info.Defs[n])
- }
- // Anonymous receiver? No need to spill.
- if field.Names == nil {
- f.addParamObj(f.Signature.Recv())
- }
- }
- }
-
- // 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(f.Pkg.info.Defs[n])
- }
- // Anonymous parameter? No need to spill.
- if field.Names == nil {
- f.addParamObj(f.Signature.Params().At(len(f.Params) - n))
- }
- }
- }
-
- // Named results.
- if functype.Results != nil {
- for _, field := range functype.Results.List {
- // Implicit "var" decl of locals for named results.
- for _, n := range field.Names {
- f.namedResults = append(f.namedResults, f.addLocalForIdent(n))
- }
- }
- }
-}
-
-type setNumable interface {
- setNum(int)
-}
-
-// numberRegisters assigns numbers to all SSA registers
-// (value-defining Instructions) in f, to aid debugging.
-// (Non-Instruction Values are named at construction.)
-//
-func numberRegisters(f *Function) {
- v := 0
- for _, b := range f.Blocks {
- for _, instr := range b.Instrs {
- switch instr.(type) {
- case Value:
- instr.(setNumable).setNum(v)
- v++
- }
- }
- }
-}
-
-// 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
- for _, rand := range rands {
- if r := *rand; r != nil {
- if ref := r.Referrers(); ref != nil {
- *ref = append(*ref, instr)
- }
- }
- }
- }
- }
-}
-
-// finishBody() finalizes the function after SSA code generation of its body.
-func (f *Function) finishBody() {
- f.objects = nil
- f.currentBlock = nil
- f.lblocks = nil
-
- // Don't pin the AST in memory (except in debug mode).
- if n := f.syntax; n != nil && !f.debugInfo() {
- f.syntax = extentNode{n.Pos(), n.End()}
- }
-
- // 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)
-
- if f.Prog.mode&NaiveForm == 0 {
- // For debugging pre-state of lifting pass:
- // numberRegisters(f)
- // f.WriteTo(os.Stderr)
- lift(f)
- }
-
- f.namedResults = nil // (used by lifting)
-
- numberRegisters(f)
-
- if f.Prog.mode&PrintFunctions != 0 {
- printMu.Lock()
- f.WriteTo(os.Stdout)
- printMu.Unlock()
- }
-
- if f.Prog.mode&SanityCheckFunctions != 0 {
- mustSanityCheck(f, nil)
- }
-}
-
-// 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) {
- // TODO(adonovan): do we want ast.File granularity?
- pkg.debug = debug
-}
-
-// debugInfo reports whether debug info is wanted for this function.
-func (f *Function) debugInfo() bool {
- return f.Pkg != nil && f.Pkg.debug
-}
-
-// addNamedLocal creates a local variable, adds it to function f and
-// returns it. Its name and type are taken from obj. Subsequent
-// calls to f.lookup(obj) will return the same local.
-//
-func (f *Function) addNamedLocal(obj types.Object) *Alloc {
- l := f.addLocal(obj.Type(), obj.Pos())
- l.Comment = obj.Name()
- f.objects[obj] = l
- return l
-}
-
-func (f *Function) addLocalForIdent(id *ast.Ident) *Alloc {
- return f.addNamedLocal(f.Pkg.info.Defs[id])
-}
-
-// addLocal creates an anonymous local variable of type typ, adds it
-// to function f and returns it. pos is the optional source location.
-//
-func (f *Function) addLocal(typ types.Type, pos token.Pos) *Alloc {
- v := &Alloc{}
- v.setType(types.NewPointer(typ))
- v.setPos(pos)
- f.Locals = append(f.Locals, v)
- f.emit(v)
- return v
-}
-
-// 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.
-//
-func (f *Function) lookup(obj types.Object, escaping bool) Value {
- if v, ok := f.objects[obj]; ok {
- if alloc, ok := v.(*Alloc); ok && escaping {
- 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 ssa.Value for " + obj.String())
- }
- outer := f.parent.lookup(obj, true) // escaping
- v := &FreeVar{
- name: obj.Name(),
- typ: outer.Type(),
- pos: outer.Pos(),
- outer: outer,
- parent: f,
- }
- f.objects[obj] = v
- f.FreeVars = append(f.FreeVars, v)
- return v
-}
-
-// emit emits the specified instruction to function f.
-func (f *Function) emit(instr Instruction) Value {
- return f.currentBlock.emit(instr)
-}
-
-// 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.pkg(); 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, params []*Parameter) {
- buf.WriteString("func ")
- if recv := sig.Recv(); recv != nil {
- buf.WriteString("(")
- if n := params[0].Name(); n != "" {
- buf.WriteString(n)
- buf.WriteString(" ")
- }
- types.WriteType(buf, params[0].Type(), types.RelativeTo(from))
- buf.WriteString(") ")
- }
- buf.WriteString(name)
- types.WriteSignature(buf, sig, types.RelativeTo(from))
-}
-
-func (f *Function) pkg() *types.Package {
- if f.Pkg != nil {
- return f.Pkg.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())
- }
-
- if f.Recover != nil {
- fmt.Fprintf(buf, "# Recover: %s\n", f.Recover)
- }
-
- from := f.pkg()
-
- if f.FreeVars != nil {
- buf.WriteString("# Free variables:\n")
- for i, fv := range f.FreeVars {
- fmt.Fprintf(buf, "# % 3d:\t%s %s\n", i, 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:\t%s %s\n", i, l.Name(), relType(deref(l.Type()), from))
- }
- }
- writeSignature(buf, from, f.Name(), f.Signature, f.Params)
- buf.WriteString(":\n")
-
- if f.Blocks == nil {
- buf.WriteString("\t(external)\n")
- }
-
- // NB. column calculations are confused by non-ASCII
- // characters and assume 8-space tabs.
- const punchcard = 80 // for old time's sake.
- const tabwidth = 8
- for _, b := range f.Blocks {
- if b == nil {
- // Corrupt CFG.
- fmt.Fprintf(buf, ".nil:\n")
- continue
- }
- n, _ := fmt.Fprintf(buf, "%d:", b.Index)
- bmsg := fmt.Sprintf("%s P:%d S:%d", b.Comment, len(b.Preds), len(b.Succs))
- fmt.Fprintf(buf, "%*s%s\n", punchcard-1-n-len(bmsg), "", bmsg)
-
- if false { // CFG debugging
- fmt.Fprintf(buf, "\t# CFG: %s --> %s --> %s\n", b.Preds, b, b.Succs)
- }
- for _, instr := range b.Instrs {
- buf.WriteString("\t")
- switch v := instr.(type) {
- case Value:
- l := punchcard - tabwidth
- // 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())
- }
- buf.WriteString("\n")
- }
- }
- fmt.Fprintf(buf, "\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
-// SSA 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}
-}
-
-type extentNode [2]token.Pos
-
-func (n extentNode) Pos() token.Pos { return n[0] }
-func (n extentNode) End() token.Pos { return n[1] }
-
-// Syntax returns an ast.Node whose Pos/End methods provide the
-// lexical extent of the function if it was defined by Go source code
-// (f.Synthetic==""), or nil otherwise.
-//
-// If f was built with debug information (see Package.SetDebugRef),
-// the result is the *ast.FuncDecl or *ast.FuncLit that declared the
-// function. Otherwise, it is an opaque Node providing only position
-// information; this avoids pinning the AST in memory.
-//
-func (f *Function) Syntax() ast.Node { return f.syntax }
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