| // 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 |
| |
| // An optional pass for sanity-checking invariants of the SSA representation. |
| // Currently it checks CFG invariants but little at the instruction level. |
| |
| import ( |
| "fmt" |
| "io" |
| "os" |
| "strings" |
| |
| "code.google.com/p/go.tools/go/types" |
| ) |
| |
| type sanity struct { |
| reporter io.Writer |
| fn *Function |
| block *BasicBlock |
| insane bool |
| } |
| |
| // sanityCheck performs integrity checking of the SSA representation |
| // of the function fn and returns true if it was valid. Diagnostics |
| // are written to reporter if non-nil, os.Stderr otherwise. Some |
| // diagnostics are only warnings and do not imply a negative result. |
| // |
| // Sanity-checking is intended to facilitate the debugging of code |
| // transformation passes. |
| // |
| func sanityCheck(fn *Function, reporter io.Writer) bool { |
| if reporter == nil { |
| reporter = os.Stderr |
| } |
| return (&sanity{reporter: reporter}).checkFunction(fn) |
| } |
| |
| // mustSanityCheck is like sanityCheck but panics instead of returning |
| // a negative result. |
| // |
| func mustSanityCheck(fn *Function, reporter io.Writer) { |
| if !sanityCheck(fn, reporter) { |
| fn.DumpTo(os.Stderr) |
| panic("SanityCheck failed") |
| } |
| } |
| |
| func (s *sanity) diagnostic(prefix, format string, args ...interface{}) { |
| fmt.Fprintf(s.reporter, "%s: function %s", prefix, s.fn) |
| if s.block != nil { |
| fmt.Fprintf(s.reporter, ", block %s", s.block) |
| } |
| io.WriteString(s.reporter, ": ") |
| fmt.Fprintf(s.reporter, format, args...) |
| io.WriteString(s.reporter, "\n") |
| } |
| |
| func (s *sanity) errorf(format string, args ...interface{}) { |
| s.insane = true |
| s.diagnostic("Error", format, args...) |
| } |
| |
| func (s *sanity) warnf(format string, args ...interface{}) { |
| s.diagnostic("Warning", format, args...) |
| } |
| |
| // findDuplicate returns an arbitrary basic block that appeared more |
| // than once in blocks, or nil if all were unique. |
| func findDuplicate(blocks []*BasicBlock) *BasicBlock { |
| if len(blocks) < 2 { |
| return nil |
| } |
| if blocks[0] == blocks[1] { |
| return blocks[0] |
| } |
| // Slow path: |
| m := make(map[*BasicBlock]bool) |
| for _, b := range blocks { |
| if m[b] { |
| return b |
| } |
| m[b] = true |
| } |
| return nil |
| } |
| |
| func (s *sanity) checkInstr(idx int, instr Instruction) { |
| switch instr := instr.(type) { |
| case *If, *Jump, *Ret, *Panic: |
| s.errorf("control flow instruction not at end of block") |
| case *Phi: |
| if idx == 0 { |
| // It suffices to apply this check to just the first phi node. |
| if dup := findDuplicate(s.block.Preds); dup != nil { |
| s.errorf("phi node in block with duplicate predecessor %s", dup) |
| } |
| } else { |
| prev := s.block.Instrs[idx-1] |
| if _, ok := prev.(*Phi); !ok { |
| s.errorf("Phi instruction follows a non-Phi: %T", prev) |
| } |
| } |
| if ne, np := len(instr.Edges), len(s.block.Preds); ne != np { |
| s.errorf("phi node has %d edges but %d predecessors", ne, np) |
| |
| } else { |
| for i, e := range instr.Edges { |
| if e == nil { |
| s.errorf("phi node '%s' has no value for edge #%d from %s", instr.Comment, i, s.block.Preds[i]) |
| } |
| } |
| } |
| |
| case *Alloc: |
| if !instr.Heap { |
| found := false |
| for _, l := range s.fn.Locals { |
| if l == instr { |
| found = true |
| break |
| } |
| } |
| if !found { |
| s.errorf("local alloc %s = %s does not appear in Function.Locals", instr.Name(), instr) |
| } |
| } |
| |
| case *BinOp: |
| case *Call: |
| case *ChangeInterface: |
| case *ChangeType: |
| case *Convert: |
| if _, ok := instr.X.Type().Underlying().(*types.Basic); !ok { |
| if _, ok := instr.Type().Underlying().(*types.Basic); !ok { |
| s.errorf("convert %s -> %s: at least one type must be basic", instr.X.Type(), instr.Type()) |
| } |
| } |
| case *Defer: |
| case *Extract: |
| case *Field: |
| case *FieldAddr: |
| case *Go: |
| case *Index: |
| case *IndexAddr: |
| case *Lookup: |
| case *MakeChan: |
| case *MakeClosure: |
| numFree := len(instr.Fn.(*Function).FreeVars) |
| numBind := len(instr.Bindings) |
| if numFree != numBind { |
| s.errorf("MakeClosure has %d Bindings for function %s with %d free vars", |
| numBind, instr.Fn, numFree) |
| |
| } |
| if recv := instr.Type().(*types.Signature).Recv(); recv != nil { |
| s.errorf("MakeClosure's type includes receiver %s", recv.Type()) |
| } |
| |
| case *MakeInterface: |
| case *MakeMap: |
| case *MakeSlice: |
| case *MapUpdate: |
| case *Next: |
| case *Range: |
| case *RunDefers: |
| case *Select: |
| case *Send: |
| case *Slice: |
| case *Store: |
| case *TypeAssert: |
| case *UnOp: |
| case *DebugRef: |
| // TODO(adonovan): implement checks. |
| default: |
| panic(fmt.Sprintf("Unknown instruction type: %T", instr)) |
| } |
| |
| // Check that value-defining instructions have valid types. |
| if v, ok := instr.(Value); ok { |
| t := v.Type() |
| if t == nil { |
| s.errorf("no type: %s = %s", v.Name(), v) |
| } else if t == tRangeIter { |
| // not a proper type; ignore. |
| } else if b, ok := t.Underlying().(*types.Basic); ok && b.Info()&types.IsUntyped != 0 { |
| s.errorf("instruction has 'untyped' result: %s = %s : %s", v.Name(), v, t) |
| } |
| } |
| |
| // TODO(adonovan): sanity-check Consts used as instruction Operands(), |
| // e.g. reject Consts with "untyped" types. |
| // |
| // All other non-Instruction Values can be found via their |
| // enclosing Function or Package. |
| } |
| |
| func (s *sanity) checkFinalInstr(idx int, instr Instruction) { |
| switch instr.(type) { |
| case *If: |
| if nsuccs := len(s.block.Succs); nsuccs != 2 { |
| s.errorf("If-terminated block has %d successors; expected 2", nsuccs) |
| return |
| } |
| if s.block.Succs[0] == s.block.Succs[1] { |
| s.errorf("If-instruction has same True, False target blocks: %s", s.block.Succs[0]) |
| return |
| } |
| |
| case *Jump: |
| if nsuccs := len(s.block.Succs); nsuccs != 1 { |
| s.errorf("Jump-terminated block has %d successors; expected 1", nsuccs) |
| return |
| } |
| |
| case *Ret: |
| if nsuccs := len(s.block.Succs); nsuccs != 0 { |
| s.errorf("Ret-terminated block has %d successors; expected none", nsuccs) |
| return |
| } |
| // TODO(adonovan): check number and types of results |
| |
| case *Panic: |
| if nsuccs := len(s.block.Succs); nsuccs != 0 { |
| s.errorf("Panic-terminated block has %d successors; expected none", nsuccs) |
| return |
| } |
| |
| default: |
| s.errorf("non-control flow instruction at end of block") |
| } |
| } |
| |
| func (s *sanity) checkBlock(b *BasicBlock, index int) { |
| s.block = b |
| |
| if b.Index != index { |
| s.errorf("block has incorrect Index %d", b.Index) |
| } |
| if b.parent != s.fn { |
| s.errorf("block has incorrect parent %s", b.parent) |
| } |
| |
| // Check all blocks are reachable. |
| // (The entry block is always implicitly reachable.) |
| if index > 0 && len(b.Preds) == 0 { |
| s.warnf("unreachable block") |
| if b.Instrs == nil { |
| // Since this block is about to be pruned, |
| // tolerating transient problems in it |
| // simplifies other optimizations. |
| return |
| } |
| } |
| |
| // Check predecessor and successor relations are dual, |
| // and that all blocks in CFG belong to same function. |
| for _, a := range b.Preds { |
| found := false |
| for _, bb := range a.Succs { |
| if bb == b { |
| found = true |
| break |
| } |
| } |
| if !found { |
| s.errorf("expected successor edge in predecessor %s; found only: %s", a, a.Succs) |
| } |
| if a.parent != s.fn { |
| s.errorf("predecessor %s belongs to different function %s", a, a.parent) |
| } |
| } |
| for _, c := range b.Succs { |
| found := false |
| for _, bb := range c.Preds { |
| if bb == b { |
| found = true |
| break |
| } |
| } |
| if !found { |
| s.errorf("expected predecessor edge in successor %s; found only: %s", c, c.Preds) |
| } |
| if c.parent != s.fn { |
| s.errorf("successor %s belongs to different function %s", c, c.parent) |
| } |
| } |
| |
| // Check each instruction is sane. |
| // TODO(adonovan): check Instruction invariants: |
| // - check Operands is dual to Value.Referrers. |
| // - check all Operands that are also Instructions belong to s.fn too |
| // (and for bonus marks, that their block dominates block b). |
| n := len(b.Instrs) |
| if n == 0 { |
| s.errorf("basic block contains no instructions") |
| } |
| for j, instr := range b.Instrs { |
| if instr == nil { |
| s.errorf("nil instruction at index %d", j) |
| continue |
| } |
| if b2 := instr.Block(); b2 == nil { |
| s.errorf("nil Block() for instruction at index %d", j) |
| continue |
| } else if b2 != b { |
| s.errorf("wrong Block() (%s) for instruction at index %d ", b2, j) |
| continue |
| } |
| if j < n-1 { |
| s.checkInstr(j, instr) |
| } else { |
| s.checkFinalInstr(j, instr) |
| } |
| } |
| } |
| |
| func (s *sanity) checkFunction(fn *Function) bool { |
| // TODO(adonovan): check Function invariants: |
| // - check params match signature |
| // - check transient fields are nil |
| // - warn if any fn.Locals do not appear among block instructions. |
| s.fn = fn |
| if fn.Prog == nil { |
| s.errorf("nil Prog") |
| } |
| // All functions have a package, except wrappers for error.Error() |
| // (and embedding of that method in other interfaces). |
| if fn.Pkg == nil { |
| if strings.Contains(fn.Synthetic, "wrapper") && |
| strings.HasSuffix(fn.name, "Error") { |
| // wrapper for error.Error() has no package. |
| } else { |
| s.errorf("nil Pkg") |
| } |
| } |
| for i, l := range fn.Locals { |
| if l.Parent() != fn { |
| s.errorf("Local %s at index %d has wrong parent", l.Name(), i) |
| } |
| if l.Heap { |
| s.errorf("Local %s at index %d has Heap flag set", l.Name(), i) |
| } |
| } |
| for i, p := range fn.Params { |
| if p.Parent() != fn { |
| s.errorf("Param %s at index %d has wrong parent", p.Name(), i) |
| } |
| } |
| for i, fv := range fn.FreeVars { |
| if fv.Parent() != fn { |
| s.errorf("FreeVar %s at index %d has wrong parent", fv.Name(), i) |
| } |
| } |
| |
| if fn.Blocks != nil && len(fn.Blocks) == 0 { |
| // Function _had_ blocks (so it's not external) but |
| // they were "optimized" away, even the entry block. |
| s.errorf("Blocks slice is non-nil but empty") |
| } |
| for i, b := range fn.Blocks { |
| if b == nil { |
| s.warnf("nil *BasicBlock at f.Blocks[%d]", i) |
| continue |
| } |
| s.checkBlock(b, i) |
| } |
| s.block = nil |
| s.fn = nil |
| return !s.insane |
| } |
| |
| // sanityCheckPackage checks invariants of packages upon creation. |
| // It does not require that the package is built. |
| // Unlike sanityCheck (for functions), it just panics at the first error. |
| func sanityCheckPackage(pkg *Package) { |
| for name, mem := range pkg.Members { |
| if name != mem.Name() { |
| panic(fmt.Sprintf("%s: %T.Name() = %s, want %s", |
| pkg.Object.Path(), mem, mem.Name(), name)) |
| } |
| obj := mem.Object() |
| if obj == nil { |
| // This check is sound because fields |
| // {Global,Function}.object have type |
| // types.Object. (If they were declared as |
| // *types.{Var,Func}, we'd have a non-empty |
| // interface containing a nil pointer.) |
| |
| continue // not all members have typechecker objects |
| } |
| if obj.Name() != name { |
| panic(fmt.Sprintf("%s: %T.Object().Name() = %s, want %s", |
| pkg.Object.Path(), mem, obj.Name(), name)) |
| } |
| if obj.Pos() != mem.Pos() { |
| panic(fmt.Sprintf("%s Pos=%d obj.Pos=%d", mem, mem.Pos(), obj.Pos())) |
| } |
| } |
| } |