272 lines
7 KiB
Go
272 lines
7 KiB
Go
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package ir
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import (
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"go/types"
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)
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func (b *builder) buildExits(fn *Function) {
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if obj := fn.Object(); obj != nil {
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switch obj.Pkg().Path() {
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case "runtime":
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switch obj.Name() {
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case "exit":
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fn.WillExit = true
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return
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case "throw":
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fn.WillExit = true
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return
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case "Goexit":
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fn.WillUnwind = true
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return
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}
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case "github.com/sirupsen/logrus":
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switch obj.(*types.Func).FullName() {
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case "(*github.com/sirupsen/logrus.Logger).Exit":
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// Technically, this method does not unconditionally exit
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// the process. It dynamically calls a function stored in
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// the logger. If the function is nil, it defaults to
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// os.Exit.
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//
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// The main intent of this method is to terminate the
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// process, and that's what the vast majority of people
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// will use it for. We'll happily accept some false
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// negatives to avoid a lot of false positives.
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fn.WillExit = true
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return
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case "(*github.com/sirupsen/logrus.Logger).Panic",
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"(*github.com/sirupsen/logrus.Logger).Panicf",
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"(*github.com/sirupsen/logrus.Logger).Panicln":
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// These methods will always panic, but that's not
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// statically known from the code alone, because they
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// take a detour through the generic Log methods.
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fn.WillUnwind = true
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return
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case "(*github.com/sirupsen/logrus.Entry).Panicf",
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"(*github.com/sirupsen/logrus.Entry).Panicln":
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// Entry.Panic has an explicit panic, but Panicf and
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// Panicln do not, relying fully on the generic Log
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// method.
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fn.WillUnwind = true
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return
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case "(*github.com/sirupsen/logrus.Logger).Log",
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"(*github.com/sirupsen/logrus.Logger).Logf",
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"(*github.com/sirupsen/logrus.Logger).Logln":
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// TODO(dh): we cannot handle these case. Whether they
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// exit or unwind depends on the level, which is set
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// via the first argument. We don't currently support
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// call-site-specific exit information.
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}
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}
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}
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buildDomTree(fn)
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isRecoverCall := func(instr Instruction) bool {
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if instr, ok := instr.(*Call); ok {
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if builtin, ok := instr.Call.Value.(*Builtin); ok {
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if builtin.Name() == "recover" {
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return true
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}
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}
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}
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return false
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}
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// All panics branch to the exit block, which means that if every
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// possible path through the function panics, then all
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// predecessors of the exit block must panic.
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willPanic := true
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for _, pred := range fn.Exit.Preds {
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if _, ok := pred.Control().(*Panic); !ok {
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willPanic = false
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}
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}
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if willPanic {
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recovers := false
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recoverLoop:
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for _, u := range fn.Blocks {
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for _, instr := range u.Instrs {
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if instr, ok := instr.(*Defer); ok {
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call := instr.Call.StaticCallee()
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if call == nil {
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// not a static call, so we can't be sure the
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// deferred call isn't calling recover
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recovers = true
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break recoverLoop
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}
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if len(call.Blocks) == 0 {
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// external function, we don't know what's
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// happening inside it
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//
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// TODO(dh): this includes functions from
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// imported packages, due to how go/analysis
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// works. We could introduce another fact,
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// like we've done for exiting and unwinding,
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// but it doesn't seem worth it. Virtually all
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// uses of recover will be in closures.
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recovers = true
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break recoverLoop
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}
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for _, y := range call.Blocks {
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for _, instr2 := range y.Instrs {
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if isRecoverCall(instr2) {
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recovers = true
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break recoverLoop
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}
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}
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}
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}
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}
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}
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if !recovers {
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fn.WillUnwind = true
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return
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}
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}
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// TODO(dh): don't check that any specific call dominates the exit
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// block. instead, check that all calls combined cover every
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// possible path through the function.
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exits := NewBlockSet(len(fn.Blocks))
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unwinds := NewBlockSet(len(fn.Blocks))
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for _, u := range fn.Blocks {
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for _, instr := range u.Instrs {
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if instr, ok := instr.(CallInstruction); ok {
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switch instr.(type) {
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case *Defer, *Call:
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default:
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continue
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}
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if instr.Common().IsInvoke() {
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// give up
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return
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}
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var call *Function
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switch instr.Common().Value.(type) {
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case *Function, *MakeClosure:
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call = instr.Common().StaticCallee()
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case *Builtin:
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// the only builtins that affect control flow are
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// panic and recover, and we've already handled
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// those
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continue
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default:
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// dynamic dispatch
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return
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}
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// buildFunction is idempotent. if we're part of a
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// (mutually) recursive call chain, then buildFunction
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// will immediately return, and fn.WillExit will be false.
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if call.Package() == fn.Package() {
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b.buildFunction(call)
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}
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dom := u.Dominates(fn.Exit)
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if call.WillExit {
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if dom {
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fn.WillExit = true
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return
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}
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exits.Add(u)
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} else if call.WillUnwind {
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if dom {
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fn.WillUnwind = true
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return
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}
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unwinds.Add(u)
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}
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}
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}
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}
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// depth-first search trying to find a path to the exit block that
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// doesn't cross any of the blacklisted blocks
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seen := NewBlockSet(len(fn.Blocks))
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var findPath func(root *BasicBlock, bl *BlockSet) bool
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findPath = func(root *BasicBlock, bl *BlockSet) bool {
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if root == fn.Exit {
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return true
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}
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if seen.Has(root) {
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return false
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}
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if bl.Has(root) {
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return false
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}
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seen.Add(root)
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for _, succ := range root.Succs {
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if findPath(succ, bl) {
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return true
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}
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}
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return false
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}
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if exits.Num() > 0 {
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if !findPath(fn.Blocks[0], exits) {
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fn.WillExit = true
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return
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}
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}
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if unwinds.Num() > 0 {
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seen.Clear()
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if !findPath(fn.Blocks[0], unwinds) {
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fn.WillUnwind = true
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return
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}
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}
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}
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func (b *builder) addUnreachables(fn *Function) {
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for _, bb := range fn.Blocks {
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for i, instr := range bb.Instrs {
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if instr, ok := instr.(*Call); ok {
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var call *Function
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switch v := instr.Common().Value.(type) {
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case *Function:
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call = v
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case *MakeClosure:
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call = v.Fn.(*Function)
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}
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if call == nil {
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continue
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}
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if call.Package() == fn.Package() {
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// make sure we have information on all functions in this package
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b.buildFunction(call)
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}
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if call.WillExit {
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// This call will cause the process to terminate.
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// Remove remaining instructions in the block and
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// replace any control flow with Unreachable.
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for _, succ := range bb.Succs {
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succ.removePred(bb)
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}
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bb.Succs = bb.Succs[:0]
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bb.Instrs = bb.Instrs[:i+1]
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bb.emit(new(Unreachable), instr.Source())
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addEdge(bb, fn.Exit)
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break
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} else if call.WillUnwind {
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// This call will cause the goroutine to terminate
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// and defers to run (i.e. a panic or
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// runtime.Goexit). Remove remaining instructions
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// in the block and replace any control flow with
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// an unconditional jump to the exit block.
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for _, succ := range bb.Succs {
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succ.removePred(bb)
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}
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bb.Succs = bb.Succs[:0]
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bb.Instrs = bb.Instrs[:i+1]
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bb.emit(new(Jump), instr.Source())
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addEdge(bb, fn.Exit)
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break
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}
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}
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}
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}
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}
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