1 // Copyright 2013 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
7 // An optional pass for sanity-checking invariants of the SSA representation.
8 // Currently it checks CFG invariants but little at the instruction level.
22 instrs map[Instruction]struct{}
26 // sanityCheck performs integrity checking of the SSA representation
27 // of the function fn and returns true if it was valid. Diagnostics
28 // are written to reporter if non-nil, os.Stderr otherwise. Some
29 // diagnostics are only warnings and do not imply a negative result.
31 // Sanity-checking is intended to facilitate the debugging of code
32 // transformation passes.
34 func sanityCheck(fn *Function, reporter io.Writer) bool {
38 return (&sanity{reporter: reporter}).checkFunction(fn)
41 // mustSanityCheck is like sanityCheck but panics instead of returning
44 func mustSanityCheck(fn *Function, reporter io.Writer) {
45 if !sanityCheck(fn, reporter) {
47 panic("SanityCheck failed")
51 func (s *sanity) diagnostic(prefix, format string, args ...interface{}) {
52 fmt.Fprintf(s.reporter, "%s: function %s", prefix, s.fn)
54 fmt.Fprintf(s.reporter, ", block %s", s.block)
56 io.WriteString(s.reporter, ": ")
57 fmt.Fprintf(s.reporter, format, args...)
58 io.WriteString(s.reporter, "\n")
61 func (s *sanity) errorf(format string, args ...interface{}) {
63 s.diagnostic("Error", format, args...)
66 func (s *sanity) warnf(format string, args ...interface{}) {
67 s.diagnostic("Warning", format, args...)
70 // findDuplicate returns an arbitrary basic block that appeared more
71 // than once in blocks, or nil if all were unique.
72 func findDuplicate(blocks []*BasicBlock) *BasicBlock {
76 if blocks[0] == blocks[1] {
80 m := make(map[*BasicBlock]bool)
81 for _, b := range blocks {
90 func (s *sanity) checkInstr(idx int, instr Instruction) {
91 switch instr := instr.(type) {
92 case *If, *Jump, *Return, *Panic:
93 s.errorf("control flow instruction not at end of block")
96 // It suffices to apply this check to just the first phi node.
97 if dup := findDuplicate(s.block.Preds); dup != nil {
98 s.errorf("phi node in block with duplicate predecessor %s", dup)
101 prev := s.block.Instrs[idx-1]
102 if _, ok := prev.(*Phi); !ok {
103 s.errorf("Phi instruction follows a non-Phi: %T", prev)
106 if ne, np := len(instr.Edges), len(s.block.Preds); ne != np {
107 s.errorf("phi node has %d edges but %d predecessors", ne, np)
110 for i, e := range instr.Edges {
112 s.errorf("phi node '%s' has no value for edge #%d from %s", instr.Comment, i, s.block.Preds[i])
120 for _, l := range s.fn.Locals {
127 s.errorf("local alloc %s = %s does not appear in Function.Locals", instr.Name(), instr)
133 case *ChangeInterface:
136 if _, ok := instr.X.Type().Underlying().(*types.Basic); !ok {
137 if _, ok := instr.Type().Underlying().(*types.Basic); !ok {
138 s.errorf("convert %s -> %s: at least one type must be basic", instr.X.Type(), instr.Type())
152 numFree := len(instr.Fn.(*Function).FreeVars)
153 numBind := len(instr.Bindings)
154 if numFree != numBind {
155 s.errorf("MakeClosure has %d Bindings for function %s with %d free vars",
156 numBind, instr.Fn, numFree)
159 if recv := instr.Type().(*types.Signature).Recv(); recv != nil {
160 s.errorf("MakeClosure's type includes receiver %s", recv.Type())
177 // TODO(adonovan): implement checks.
179 panic(fmt.Sprintf("Unknown instruction type: %T", instr))
182 if call, ok := instr.(CallInstruction); ok {
183 if call.Common().Signature() == nil {
184 s.errorf("nil signature: %s", call)
188 // Check that value-defining instructions have valid types
189 // and a valid referrer list.
190 if v, ok := instr.(Value); ok {
193 s.errorf("no type: %s = %s", v.Name(), v)
194 } else if t == tRangeIter {
195 // not a proper type; ignore.
196 } else if b, ok := t.Underlying().(*types.Basic); ok && b.Info()&types.IsUntyped != 0 {
197 s.errorf("instruction has 'untyped' result: %s = %s : %s", v.Name(), v, t)
199 s.checkReferrerList(v)
202 // Untyped constants are legal as instruction Operands(),
206 // if wordsize==64 {...}
208 // All other non-Instruction Values can be found via their
209 // enclosing Function or Package.
212 func (s *sanity) checkFinalInstr(instr Instruction) {
213 switch instr := instr.(type) {
215 if nsuccs := len(s.block.Succs); nsuccs != 2 {
216 s.errorf("If-terminated block has %d successors; expected 2", nsuccs)
219 if s.block.Succs[0] == s.block.Succs[1] {
220 s.errorf("If-instruction has same True, False target blocks: %s", s.block.Succs[0])
225 if nsuccs := len(s.block.Succs); nsuccs != 1 {
226 s.errorf("Jump-terminated block has %d successors; expected 1", nsuccs)
231 if nsuccs := len(s.block.Succs); nsuccs != 0 {
232 s.errorf("Return-terminated block has %d successors; expected none", nsuccs)
235 if na, nf := len(instr.Results), s.fn.Signature.Results().Len(); nf != na {
236 s.errorf("%d-ary return in %d-ary function", na, nf)
240 if nsuccs := len(s.block.Succs); nsuccs != 0 {
241 s.errorf("Panic-terminated block has %d successors; expected none", nsuccs)
246 s.errorf("non-control flow instruction at end of block")
250 func (s *sanity) checkBlock(b *BasicBlock, index int) {
253 if b.Index != index {
254 s.errorf("block has incorrect Index %d", b.Index)
256 if b.parent != s.fn {
257 s.errorf("block has incorrect parent %s", b.parent)
260 // Check all blocks are reachable.
261 // (The entry block is always implicitly reachable,
262 // as is the Recover block, if any.)
263 if (index > 0 && b != b.parent.Recover) && len(b.Preds) == 0 {
264 s.warnf("unreachable block")
266 // Since this block is about to be pruned,
267 // tolerating transient problems in it
268 // simplifies other optimizations.
273 // Check predecessor and successor relations are dual,
274 // and that all blocks in CFG belong to same function.
275 for _, a := range b.Preds {
277 for _, bb := range a.Succs {
284 s.errorf("expected successor edge in predecessor %s; found only: %s", a, a.Succs)
286 if a.parent != s.fn {
287 s.errorf("predecessor %s belongs to different function %s", a, a.parent)
290 for _, c := range b.Succs {
292 for _, bb := range c.Preds {
299 s.errorf("expected predecessor edge in successor %s; found only: %s", c, c.Preds)
301 if c.parent != s.fn {
302 s.errorf("successor %s belongs to different function %s", c, c.parent)
306 // Check each instruction is sane.
309 s.errorf("basic block contains no instructions")
311 var rands [10]*Value // reuse storage
312 for j, instr := range b.Instrs {
314 s.errorf("nil instruction at index %d", j)
317 if b2 := instr.Block(); b2 == nil {
318 s.errorf("nil Block() for instruction at index %d", j)
321 s.errorf("wrong Block() (%s) for instruction at index %d ", b2, j)
325 s.checkInstr(j, instr)
327 s.checkFinalInstr(instr)
330 // Check Instruction.Operands.
332 for i, op := range instr.Operands(rands[:0]) {
334 s.errorf("nil operand pointer %d of %s", i, instr)
339 continue // a nil operand is ok
342 // Check that "untyped" types only appear on constant operands.
343 if _, ok := (*op).(*Const); !ok {
344 if basic, ok := (*op).Type().(*types.Basic); ok {
345 if basic.Info()&types.IsUntyped != 0 {
346 s.errorf("operand #%d of %s is untyped: %s", i, instr, basic)
351 // Check that Operands that are also Instructions belong to same function.
352 // TODO(adonovan): also check their block dominates block b.
353 if val, ok := val.(Instruction); ok {
354 if val.Block() == nil {
355 s.errorf("operand %d of %s is an instruction (%s) that belongs to no block", i, instr, val)
356 } else if val.Parent() != s.fn {
357 s.errorf("operand %d of %s is an instruction (%s) from function %s", i, instr, val, val.Parent())
361 // Check that each function-local operand of
362 // instr refers back to instr. (NB: quadratic)
363 switch val := val.(type) {
364 case *Const, *Global, *Builtin:
365 continue // not local
367 if val.parent == nil {
368 continue // only anon functions are local
372 // TODO(adonovan): check val.Parent() != nil <=> val.Referrers() is defined.
374 if refs := val.Referrers(); refs != nil {
375 for _, ref := range *refs {
380 s.errorf("operand %d of %s (%s) does not refer to us", i, instr, val)
382 s.errorf("operand %d of %s (%s) has no referrers", i, instr, val)
388 func (s *sanity) checkReferrerList(v Value) {
389 refs := v.Referrers()
391 s.errorf("%s has missing referrer list", v.Name())
394 for i, ref := range *refs {
395 if _, ok := s.instrs[ref]; !ok {
396 s.errorf("%s.Referrers()[%d] = %s is not an instruction belonging to this function", v.Name(), i, ref)
401 func (s *sanity) checkFunction(fn *Function) bool {
402 // TODO(adonovan): check Function invariants:
403 // - check params match signature
404 // - check transient fields are nil
405 // - warn if any fn.Locals do not appear among block instructions.
411 _ = fn.String() // must not crash
412 _ = fn.RelString(fn.pkg()) // must not crash
414 // All functions have a package, except delegates (which are
415 // shared across packages, or duplicated as weak symbols in a
416 // separate-compilation model), and error.Error.
418 if strings.HasPrefix(fn.Synthetic, "wrapper ") ||
419 strings.HasPrefix(fn.Synthetic, "bound ") ||
420 strings.HasPrefix(fn.Synthetic, "thunk ") ||
421 strings.HasSuffix(fn.name, "Error") {
427 if src, syn := fn.Synthetic == "", fn.Syntax() != nil; src != syn {
428 s.errorf("got fromSource=%t, hasSyntax=%t; want same values", src, syn)
430 for i, l := range fn.Locals {
431 if l.Parent() != fn {
432 s.errorf("Local %s at index %d has wrong parent", l.Name(), i)
435 s.errorf("Local %s at index %d has Heap flag set", l.Name(), i)
438 // Build the set of valid referrers.
439 s.instrs = make(map[Instruction]struct{})
440 for _, b := range fn.Blocks {
441 for _, instr := range b.Instrs {
442 s.instrs[instr] = struct{}{}
445 for i, p := range fn.Params {
446 if p.Parent() != fn {
447 s.errorf("Param %s at index %d has wrong parent", p.Name(), i)
449 // Check common suffix of Signature and Params match type.
450 if sig := fn.Signature; sig != nil {
451 j := i - len(fn.Params) + sig.Params().Len() // index within sig.Params
455 if !types.Identical(p.Type(), sig.Params().At(j).Type()) {
456 s.errorf("Param %s at index %d has wrong type (%s, versus %s in Signature)", p.Name(), i, p.Type(), sig.Params().At(j).Type())
460 s.checkReferrerList(p)
462 for i, fv := range fn.FreeVars {
463 if fv.Parent() != fn {
464 s.errorf("FreeVar %s at index %d has wrong parent", fv.Name(), i)
466 s.checkReferrerList(fv)
469 if fn.Blocks != nil && len(fn.Blocks) == 0 {
470 // Function _had_ blocks (so it's not external) but
471 // they were "optimized" away, even the entry block.
472 s.errorf("Blocks slice is non-nil but empty")
474 for i, b := range fn.Blocks {
476 s.warnf("nil *BasicBlock at f.Blocks[%d]", i)
481 if fn.Recover != nil && fn.Blocks[fn.Recover.Index] != fn.Recover {
482 s.errorf("Recover block is not in Blocks slice")
486 for i, anon := range fn.AnonFuncs {
487 if anon.Parent() != fn {
488 s.errorf("AnonFuncs[%d]=%s but %s.Parent()=%s", i, anon, anon, anon.Parent())
495 // sanityCheckPackage checks invariants of packages upon creation.
496 // It does not require that the package is built.
497 // Unlike sanityCheck (for functions), it just panics at the first error.
498 func sanityCheckPackage(pkg *Package) {
500 panic(fmt.Sprintf("Package %s has no Object", pkg))
502 _ = pkg.String() // must not crash
504 for name, mem := range pkg.Members {
505 if name != mem.Name() {
506 panic(fmt.Sprintf("%s: %T.Name() = %s, want %s",
507 pkg.Pkg.Path(), mem, mem.Name(), name))
511 // This check is sound because fields
512 // {Global,Function}.object have type
513 // types.Object. (If they were declared as
514 // *types.{Var,Func}, we'd have a non-empty
515 // interface containing a nil pointer.)
517 continue // not all members have typechecker objects
519 if obj.Name() != name {
520 if obj.Name() == "init" && strings.HasPrefix(mem.Name(), "init#") {
521 // Ok. The name of a declared init function varies between
522 // its types.Func ("init") and its ssa.Function ("init#%d").
524 panic(fmt.Sprintf("%s: %T.Object().Name() = %s, want %s",
525 pkg.Pkg.Path(), mem, obj.Name(), name))
528 if obj.Pos() != mem.Pos() {
529 panic(fmt.Sprintf("%s Pos=%d obj.Pos=%d", mem, mem.Pos(), obj.Pos()))