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957 lines (857 loc) · 24.7 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 and BasicBlock types.
import (
"bytes"
"fmt"
"go/ast"
"go/format"
"go/token"
"go/types"
"io"
"os"
"sort"
"strings"
"honnef.co/go/tools/go/types/typeutil"
)
// 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)
}
// Control returns the last instruction in the block.
func (b *BasicBlock) Control() Instruction {
if len(b.Instrs) == 0 {
return nil
}
return b.Instrs[len(b.Instrs)-1]
}
// SigmaFor returns the sigma node for v coming from pred.
func (b *BasicBlock) SigmaFor(v Value, pred *BasicBlock) *Sigma {
for _, instr := range b.Instrs {
sigma, ok := instr.(*Sigma)
if !ok {
// no more sigmas
return nil
}
if sigma.From == pred && sigma.X == v {
return sigma
}
}
return nil
}
// 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, source ast.Node) Value {
i.setSource(source)
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))
}
// succIndex returns the i such that b.Succs[i] == c or -1 if there is none.
func (b *BasicBlock) succIndex(c *BasicBlock) int {
for i, succ := range b.Succs {
if succ == c {
return i
}
}
return -1
}
// hasPhi returns true if b.Instrs contains φ-nodes.
func (b *BasicBlock) hasPhi() bool {
_, ok := b.Instrs[0].(*Phi)
return ok
}
func (b *BasicBlock) Phis() []Instruction {
return b.phis()
}
// 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 {
obj := f.Pkg.info.ObjectOf(label)
if obj == nil {
// Blank label, as in '_:' - don't store to f.lblocks, this label can never be referred to; just return a fresh
// lbock.
return &lblock{_goto: f.newBasicBlock(label.Name)}
}
lb := f.lblocks[obj]
if lb == nil {
lb = &lblock{_goto: f.newBasicBlock(label.Name)}
if f.lblocks == nil {
f.lblocks = make(map[types.Object]*lblock)
}
f.lblocks[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, source ast.Node) *Parameter {
var b *BasicBlock
if len(f.Blocks) > 0 {
b = f.Blocks[0]
}
v := &Parameter{
name: name,
}
v.setBlock(b)
v.setType(typ)
v.setSource(source)
f.Params = append(f.Params, v)
if b != nil {
// There may be no blocks if this function has no body. We
// still create params, but aren't interested in the
// instruction.
f.Blocks[0].Instrs = append(f.Blocks[0].Instrs, v)
}
return v
}
func (f *Function) addParamObj(obj types.Object, source ast.Node) *Parameter {
name := obj.Name()
if name == "" {
name = fmt.Sprintf("arg%d", len(f.Params))
}
param := f.addParam(name, obj.Type(), source)
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, source ast.Node) {
param := f.addParamObj(obj, source)
spill := &Alloc{}
spill.setType(types.NewPointer(obj.Type()))
spill.source = source
f.objects[obj] = spill
f.Locals = append(f.Locals, spill)
f.emit(spill, source)
emitStore(f, spill, param, source)
// f.emit(&Store{Addr: spill, Val: param})
}
// 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.objects = make(map[types.Object]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
}
func (f *Function) exitBlock() {
old := f.currentBlock
f.Exit = f.newBasicBlock("exit")
f.currentBlock = f.Exit
ret := f.results()
results := make([]Value, len(ret))
// Run function calls deferred in this
// function when explicitly returning from it.
f.emit(new(RunDefers), nil)
for i, r := range ret {
results[i] = emitLoad(f, r, nil)
}
f.emit(&Return{Results: results}, nil)
f.currentBlock = old
}
// 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], n)
}
// Anonymous receiver? No need to spill.
if field.Names == nil {
f.addParamObj(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(f.Pkg.info.Defs[n], n)
}
// Anonymous parameter? No need to spill.
if field.Names == nil {
f.addParamObj(f.Signature.Params().At(len(f.Params)-n), field)
}
}
}
// 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))
}
}
if len(f.namedResults) == 0 {
sig := f.Signature.Results()
for i := 0; i < sig.Len(); i++ {
// XXX position information
v := f.addLocal(sig.At(i).Type(), nil)
f.implicitResults = append(f.implicitResults, v)
}
}
}
}
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)
}
}
for _, c := range f.consts {
rands = c.c.Operands(rands[:0])
updateOperandsReferrers(c.c, rands)
}
}
func (f *Function) emitConsts() {
defer func() {
f.consts = nil
f.aggregateConsts = typeutil.Map[[]*AggregateConst]{}
}()
if len(f.Blocks) == 0 {
return
}
// TODO(dh): our deduplication only works on booleans and
// integers. other constants are represented as pointers to
// things.
head := make([]constValue, 0, len(f.consts))
for _, c := range f.consts {
if len(*c.c.Referrers()) == 0 {
// TODO(dh): killing a const may make other consts dead, too
killInstruction(c.c)
} else {
head = append(head, c)
}
}
sort.Slice(head, func(i, j int) bool {
return head[i].idx < head[j].idx
})
entry := f.Blocks[0]
instrs := make([]Instruction, 0, len(entry.Instrs)+len(head))
for _, c := range head {
instrs = append(instrs, c.c)
}
f.aggregateConsts.Iterate(func(key types.Type, value []*AggregateConst) {
for _, c := range value {
instrs = append(instrs, c)
}
})
instrs = append(instrs, entry.Instrs...)
entry.Instrs = instrs
}
// buildFakeExits ensures that every block in the function is
// reachable in reverse from the Exit block. This is required to build
// a full post-dominator tree, and to ensure the exit block's
// inclusion in the dominator tree.
func buildFakeExits(fn *Function) {
// Find back-edges via forward DFS
fn.fakeExits = BlockSet{values: make([]bool, len(fn.Blocks))}
seen := fn.blockset(0)
backEdges := fn.blockset(1)
var dfs func(b *BasicBlock)
dfs = func(b *BasicBlock) {
if !seen.Add(b) {
backEdges.Add(b)
return
}
for _, pred := range b.Succs {
dfs(pred)
}
}
dfs(fn.Blocks[0])
buildLoop:
for {
seen := fn.blockset(2)
var dfs func(b *BasicBlock)
dfs = func(b *BasicBlock) {
if !seen.Add(b) {
return
}
for _, pred := range b.Preds {
dfs(pred)
}
if b == fn.Exit {
for _, b := range fn.Blocks {
if fn.fakeExits.Has(b) {
dfs(b)
}
}
}
}
dfs(fn.Exit)
for _, b := range fn.Blocks {
if !seen.Has(b) && backEdges.Has(b) {
// Block b is not reachable from the exit block. Add a
// fake jump from b to exit, then try again. Note that we
// only add one fake edge at a time, as it may make
// multiple blocks reachable.
//
// We only consider those blocks that have back edges.
// Any unreachable block that doesn't have a back edge
// must flow into a loop, which by definition has a
// back edge. Thus, by looking for loops, we should
// need fewer fake edges overall.
fn.fakeExits.Add(b)
continue buildLoop
}
}
break
}
}
// finishBody() finalizes the function after IR code generation of its body.
func (f *Function) finishBody() {
f.objects = nil
f.currentBlock = nil
f.lblocks = 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)
buildFakeExits(f)
buildReferrers(f)
buildDomTree(f)
buildPostDomTree(f)
if f.Prog.mode&NaiveForm == 0 {
for lift(f) {
}
if doSimplifyConstantCompositeValues {
for simplifyConstantCompositeValues(f) {
}
}
}
// emit constants after lifting, because lifting may produce new constants, but before other variable splitting,
// because it expects constants to have been deduplicated.
f.emitConsts()
if f.Prog.mode&SplitAfterNewInformation != 0 {
splitOnNewInformation(f.Blocks[0], &StackMap{})
}
f.namedResults = nil // (used by lifting)
f.implicitResults = nil
numberNodes(f)
defer f.wr.Close()
f.wr.WriteFunc("start", "start", f)
if f.Prog.mode&PrintFunctions != 0 {
printMu.Lock()
f.WriteTo(os.Stdout)
printMu.Unlock()
}
if f.Prog.mode&SanityCheckFunctions != 0 {
mustSanityCheck(f, nil)
}
}
func isUselessPhi(phi *Phi) (Value, bool) {
var v0 Value
for _, e := range phi.Edges {
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
}
}
return v0, true
}
func (f *Function) RemoveNilBlocks() {
f.removeNilBlocks()
}
// 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, source ast.Node) *Alloc {
l := f.addLocal(obj.Type(), source)
f.objects[obj] = l
return l
}
func (f *Function) addLocalForIdent(id *ast.Ident) *Alloc {
return f.addNamedLocal(f.Pkg.info.Defs[id], 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, source ast.Node) *Alloc {
v := &Alloc{}
v.setType(types.NewPointer(typ))
f.Locals = append(f.Locals, v)
f.emit(v, source)
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 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.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, 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.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 != 0 {
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.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")
}
for _, b := range f.Blocks {
if b == nil {
// Corrupt CFG.
fmt.Fprintf(buf, ".nil:\n")
continue
}
fmt.Fprintf(buf, "b%d:", b.Index)
if len(b.Preds) > 0 {
fmt.Fprint(buf, " ←")
for _, pred := range b.Preds {
fmt.Fprintf(buf, " b%d", pred.Index)
}
}
if b.Comment != "" {
fmt.Fprintf(buf, " # %s", b.Comment)
}
buf.WriteByte('\n')
if false { // CFG debugging
fmt.Fprintf(buf, "\t# CFG: %s --> %s --> %s\n", b.Preds, b, b.Succs)
}
buf2 := &bytes.Buffer{}
for _, instr := range b.Instrs {
buf.WriteString("\t")
switch v := instr.(type) {
case Value:
// Left-align the instruction.
if name := v.Name(); name != "" {
fmt.Fprintf(buf, "%s = ", name)
}
buf.WriteString(instr.String())
case nil:
// Be robust against bad transforms.
buf.WriteString("<deleted>")
default:
buf.WriteString(instr.String())
}
if instr != nil && instr.Comment() != "" {
buf.WriteString(" # ")
buf.WriteString(instr.Comment())
}
buf.WriteString("\n")
if f.Prog.mode&PrintSource != 0 {
if s := instr.Source(); s != nil {
buf2.Reset()
format.Node(buf2, f.Prog.Fset, s)
for {
line, err := buf2.ReadString('\n')
if len(line) == 0 {
break
}
buf.WriteString("\t\t> ")
buf.WriteString(line)
if line[len(line)-1] != '\n' {
buf.WriteString("\n")
}
if err != nil {
break
}
}
}
}
}
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 {
var instrs []Instruction
if len(f.functionBody.scratchInstructions) > 0 {
instrs = f.functionBody.scratchInstructions[0:0:avgInstructionsPerBlock]
f.functionBody.scratchInstructions = f.functionBody.scratchInstructions[avgInstructionsPerBlock:]
} else {
instrs = make([]Instruction, 0, avgInstructionsPerBlock)
}
b := &BasicBlock{
Index: len(f.Blocks),
Comment: comment,
parent: f,
Instrs: instrs,
}
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 Synthetic) *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 (f *Function) initHTML(name string) {
if name == "" {
return
}
if rel := f.RelString(nil); rel == name {
f.wr = NewHTMLWriter("ir.html", rel, "")
}
}
func killInstruction(instr Instruction) {
ops := instr.Operands(nil)
for _, op := range ops {
if refs := (*op).Referrers(); refs != nil {
*refs = removeInstr(*refs, instr)
}
}
}