| 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. |
| 4 | |
| 5 | package ssa |
| 6 | |
| 7 | // An optional pass for sanity-checking invariants of the SSA representation. |
| 8 | // Currently it checks CFG invariants but little at the instruction level. |
| 9 | |
| 10 | import ( |
| 11 | "fmt" |
| 12 | "go/types" |
| 13 | "io" |
| 14 | "os" |
| 15 | "strings" |
| 16 | ) |
| 17 | |
| 18 | type sanity struct { |
| 19 | reporter io.Writer |
| 20 | fn *Function |
| 21 | block *BasicBlock |
| 22 | instrs map[Instruction]struct{} |
| 23 | insane bool |
| 24 | } |
| 25 | |
| 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. |
| 30 | // |
| 31 | // Sanity-checking is intended to facilitate the debugging of code |
| 32 | // transformation passes. |
| 33 | func sanityCheck(fn *Function, reporter io.Writer) bool { |
| 34 | if reporter == nil { |
| 35 | reporter = os.Stderr |
| 36 | } |
| 37 | return (&sanity{reporter: reporter}).checkFunction(fn) |
| 38 | } |
| 39 | |
| 40 | // mustSanityCheck is like sanityCheck but panics instead of returning |
| 41 | // a negative result. |
| 42 | func mustSanityCheck(fn *Function, reporter io.Writer) { |
| 43 | if !sanityCheck(fn, reporter) { |
| 44 | fn.WriteTo(os.Stderr) |
| 45 | panic("SanityCheck failed") |
| 46 | } |
| 47 | } |
| 48 | |
| 49 | func (s *sanity) diagnostic(prefix, format string, args ...interface{}) { |
| 50 | fmt.Fprintf(s.reporter, "%s: function %s", prefix, s.fn) |
| 51 | if s.block != nil { |
| 52 | fmt.Fprintf(s.reporter, ", block %s", s.block) |
| 53 | } |
| 54 | io.WriteString(s.reporter, ": ") |
| 55 | fmt.Fprintf(s.reporter, format, args...) |
| 56 | io.WriteString(s.reporter, "\n") |
| 57 | } |
| 58 | |
| 59 | func (s *sanity) errorf(format string, args ...interface{}) { |
| 60 | s.insane = true |
| 61 | s.diagnostic("Error", format, args...) |
| 62 | } |
| 63 | |
| 64 | func (s *sanity) warnf(format string, args ...interface{}) { |
| 65 | s.diagnostic("Warning", format, args...) |
| 66 | } |
| 67 | |
| 68 | // findDuplicate returns an arbitrary basic block that appeared more |
| 69 | // than once in blocks, or nil if all were unique. |
| 70 | func findDuplicate(blocks []*BasicBlock) *BasicBlock { |
| 71 | if len(blocks) < 2 { |
| 72 | return nil |
| 73 | } |
| 74 | if blocks[0] == blocks[1] { |
| 75 | return blocks[0] |
| 76 | } |
| 77 | // Slow path: |
| 78 | m := make(map[*BasicBlock]bool) |
| 79 | for _, b := range blocks { |
| 80 | if m[b] { |
| 81 | return b |
| 82 | } |
| 83 | m[b] = true |
| 84 | } |
| 85 | return nil |
| 86 | } |
| 87 | |
| 88 | func (s *sanity) checkInstr(idx int, instr Instruction) { |
| 89 | switch instr := instr.(type) { |
| 90 | case *If, *Jump, *Return, *Panic: |
| 91 | s.errorf("control flow instruction not at end of block") |
| 92 | case *Phi: |
| 93 | if idx == 0 { |
| 94 | // It suffices to apply this check to just the first phi node. |
| 95 | if dup := findDuplicate(s.block.Preds); dup != nil { |
| 96 | s.errorf("phi node in block with duplicate predecessor %s", dup) |
| 97 | } |
| 98 | } else { |
| 99 | prev := s.block.Instrs[idx-1] |
| 100 | if _, ok := prev.(*Phi); !ok { |
| 101 | s.errorf("Phi instruction follows a non-Phi: %T", prev) |
| 102 | } |
| 103 | } |
| 104 | if ne, np := len(instr.Edges), len(s.block.Preds); ne != np { |
| 105 | s.errorf("phi node has %d edges but %d predecessors", ne, np) |
| 106 | |
| 107 | } else { |
| 108 | for i, e := range instr.Edges { |
| 109 | if e == nil { |
| 110 | s.errorf("phi node '%s' has no value for edge #%d from %s", instr.Comment, i, s.block.Preds[i]) |
| 111 | } |
| 112 | } |
| 113 | } |
| 114 | |
| 115 | case *Alloc: |
| 116 | if !instr.Heap { |
| 117 | found := false |
| 118 | for _, l := range s.fn.Locals { |
| 119 | if l == instr { |
| 120 | found = true |
| 121 | break |
| 122 | } |
| 123 | } |
| 124 | if !found { |
| 125 | s.errorf("local alloc %s = %s does not appear in Function.Locals", instr.Name(), instr) |
| 126 | } |
| 127 | } |
| 128 | |
| 129 | case *BinOp: |
| 130 | case *Call: |
| 131 | case *ChangeInterface: |
| 132 | case *ChangeType: |
| 133 | case *SliceToArrayPointer: |
| 134 | case *Convert: |
| 135 | if from := instr.X.Type(); !isBasicConvTypes(typeSetOf(from)) { |
| 136 | if to := instr.Type(); !isBasicConvTypes(typeSetOf(to)) { |
| 137 | s.errorf("convert %s -> %s: at least one type must be basic (or all basic, []byte, or []rune)", from, to) |
| 138 | } |
| 139 | } |
| 140 | |
| 141 | case *Defer: |
| 142 | case *Extract: |
| 143 | case *Field: |
| 144 | case *FieldAddr: |
| 145 | case *Go: |
| 146 | case *Index: |
| 147 | case *IndexAddr: |
| 148 | case *Lookup: |
| 149 | case *MakeChan: |
| 150 | case *MakeClosure: |
| 151 | numFree := len(instr.Fn.(*Function).FreeVars) |
| 152 | numBind := len(instr.Bindings) |
| 153 | if numFree != numBind { |
| 154 | s.errorf("MakeClosure has %d Bindings for function %s with %d free vars", |
| 155 | numBind, instr.Fn, numFree) |
| 156 | |
| 157 | } |
| 158 | if recv := instr.Type().(*types.Signature).Recv(); recv != nil { |
| 159 | s.errorf("MakeClosure's type includes receiver %s", recv.Type()) |
| 160 | } |
| 161 | |
| 162 | case *MakeInterface: |
| 163 | case *MakeMap: |
| 164 | case *MakeSlice: |
| 165 | case *MapUpdate: |
| 166 | case *Next: |
| 167 | case *Range: |
| 168 | case *RunDefers: |
| 169 | case *Select: |
| 170 | case *Send: |
| 171 | case *Slice: |
| 172 | case *Store: |
| 173 | case *TypeAssert: |
| 174 | case *UnOp: |
| 175 | case *DebugRef: |
| 176 | // TODO(adonovan): implement checks. |
| 177 | default: |
| 178 | panic(fmt.Sprintf("Unknown instruction type: %T", instr)) |
| 179 | } |
| 180 | |
| 181 | if call, ok := instr.(CallInstruction); ok { |
| 182 | if call.Common().Signature() == nil { |
| 183 | s.errorf("nil signature: %s", call) |
| 184 | } |
| 185 | } |
| 186 | |
| 187 | // Check that value-defining instructions have valid types |
| 188 | // and a valid referrer list. |
| 189 | if v, ok := instr.(Value); ok { |
| 190 | t := v.Type() |
| 191 | if t == nil { |
| 192 | s.errorf("no type: %s = %s", v.Name(), v) |
| 193 | } else if t == tRangeIter { |
| 194 | // not a proper type; ignore. |
| 195 | } else if b, ok := t.Underlying().(*types.Basic); ok && b.Info()&types.IsUntyped != 0 { |
| 196 | s.errorf("instruction has 'untyped' result: %s = %s : %s", v.Name(), v, t) |
| 197 | } |
| 198 | s.checkReferrerList(v) |
| 199 | } |
| 200 | |
| 201 | // Untyped constants are legal as instruction Operands(), |
| 202 | // for example: |
| 203 | // _ = "foo"[0] |
| 204 | // or: |
| 205 | // if wordsize==64 {...} |
| 206 | |
| 207 | // All other non-Instruction Values can be found via their |
| 208 | // enclosing Function or Package. |
| 209 | } |
| 210 | |
| 211 | func (s *sanity) checkFinalInstr(instr Instruction) { |
| 212 | switch instr := instr.(type) { |
| 213 | case *If: |
| 214 | if nsuccs := len(s.block.Succs); nsuccs != 2 { |
| 215 | s.errorf("If-terminated block has %d successors; expected 2", nsuccs) |
| 216 | return |
| 217 | } |
| 218 | if s.block.Succs[0] == s.block.Succs[1] { |
| 219 | s.errorf("If-instruction has same True, False target blocks: %s", s.block.Succs[0]) |
| 220 | return |
| 221 | } |
| 222 | |
| 223 | case *Jump: |
| 224 | if nsuccs := len(s.block.Succs); nsuccs != 1 { |
| 225 | s.errorf("Jump-terminated block has %d successors; expected 1", nsuccs) |
| 226 | return |
| 227 | } |
| 228 | |
| 229 | case *Return: |
| 230 | if nsuccs := len(s.block.Succs); nsuccs != 0 { |
| 231 | s.errorf("Return-terminated block has %d successors; expected none", nsuccs) |
| 232 | return |
| 233 | } |
| 234 | if na, nf := len(instr.Results), s.fn.Signature.Results().Len(); nf != na { |
| 235 | s.errorf("%d-ary return in %d-ary function", na, nf) |
| 236 | } |
| 237 | |
| 238 | case *Panic: |
| 239 | if nsuccs := len(s.block.Succs); nsuccs != 0 { |
| 240 | s.errorf("Panic-terminated block has %d successors; expected none", nsuccs) |
| 241 | return |
| 242 | } |
| 243 | |
| 244 | default: |
| 245 | s.errorf("non-control flow instruction at end of block") |
| 246 | } |
| 247 | } |
| 248 | |
| 249 | func (s *sanity) checkBlock(b *BasicBlock, index int) { |
| 250 | s.block = b |
| 251 | |
| 252 | if b.Index != index { |
| 253 | s.errorf("block has incorrect Index %d", b.Index) |
| 254 | } |
| 255 | if b.parent != s.fn { |
| 256 | s.errorf("block has incorrect parent %s", b.parent) |
| 257 | } |
| 258 | |
| 259 | // Check all blocks are reachable. |
| 260 | // (The entry block is always implicitly reachable, |
| 261 | // as is the Recover block, if any.) |
| 262 | if (index > 0 && b != b.parent.Recover) && len(b.Preds) == 0 { |
| 263 | s.warnf("unreachable block") |
| 264 | if b.Instrs == nil { |
| 265 | // Since this block is about to be pruned, |
| 266 | // tolerating transient problems in it |
| 267 | // simplifies other optimizations. |
| 268 | return |
| 269 | } |
| 270 | } |
| 271 | |
| 272 | // Check predecessor and successor relations are dual, |
| 273 | // and that all blocks in CFG belong to same function. |
| 274 | for _, a := range b.Preds { |
| 275 | found := false |
| 276 | for _, bb := range a.Succs { |
| 277 | if bb == b { |
| 278 | found = true |
| 279 | break |
| 280 | } |
| 281 | } |
| 282 | if !found { |
| 283 | s.errorf("expected successor edge in predecessor %s; found only: %s", a, a.Succs) |
| 284 | } |
| 285 | if a.parent != s.fn { |
| 286 | s.errorf("predecessor %s belongs to different function %s", a, a.parent) |
| 287 | } |
| 288 | } |
| 289 | for _, c := range b.Succs { |
| 290 | found := false |
| 291 | for _, bb := range c.Preds { |
| 292 | if bb == b { |
| 293 | found = true |
| 294 | break |
| 295 | } |
| 296 | } |
| 297 | if !found { |
| 298 | s.errorf("expected predecessor edge in successor %s; found only: %s", c, c.Preds) |
| 299 | } |
| 300 | if c.parent != s.fn { |
| 301 | s.errorf("successor %s belongs to different function %s", c, c.parent) |
| 302 | } |
| 303 | } |
| 304 | |
| 305 | // Check each instruction is sane. |
| 306 | n := len(b.Instrs) |
| 307 | if n == 0 { |
| 308 | s.errorf("basic block contains no instructions") |
| 309 | } |
| 310 | var rands [10]*Value // reuse storage |
| 311 | for j, instr := range b.Instrs { |
| 312 | if instr == nil { |
| 313 | s.errorf("nil instruction at index %d", j) |
| 314 | continue |
| 315 | } |
| 316 | if b2 := instr.Block(); b2 == nil { |
| 317 | s.errorf("nil Block() for instruction at index %d", j) |
| 318 | continue |
| 319 | } else if b2 != b { |
| 320 | s.errorf("wrong Block() (%s) for instruction at index %d ", b2, j) |
| 321 | continue |
| 322 | } |
| 323 | if j < n-1 { |
| 324 | s.checkInstr(j, instr) |
| 325 | } else { |
| 326 | s.checkFinalInstr(instr) |
| 327 | } |
| 328 | |
| 329 | // Check Instruction.Operands. |
| 330 | operands: |
| 331 | for i, op := range instr.Operands(rands[:0]) { |
| 332 | if op == nil { |
| 333 | s.errorf("nil operand pointer %d of %s", i, instr) |
| 334 | continue |
| 335 | } |
| 336 | val := *op |
| 337 | if val == nil { |
| 338 | continue // a nil operand is ok |
| 339 | } |
| 340 | |
| 341 | // Check that "untyped" types only appear on constant operands. |
| 342 | if _, ok := (*op).(*Const); !ok { |
| 343 | if basic, ok := (*op).Type().(*types.Basic); ok { |
| 344 | if basic.Info()&types.IsUntyped != 0 { |
| 345 | s.errorf("operand #%d of %s is untyped: %s", i, instr, basic) |
| 346 | } |
| 347 | } |
| 348 | } |
| 349 | |
| 350 | // Check that Operands that are also Instructions belong to same function. |
| 351 | // TODO(adonovan): also check their block dominates block b. |
| 352 | if val, ok := val.(Instruction); ok { |
| 353 | if val.Block() == nil { |
| 354 | s.errorf("operand %d of %s is an instruction (%s) that belongs to no block", i, instr, val) |
| 355 | } else if val.Parent() != s.fn { |
| 356 | s.errorf("operand %d of %s is an instruction (%s) from function %s", i, instr, val, val.Parent()) |
| 357 | } |
| 358 | } |
| 359 | |
| 360 | // Check that each function-local operand of |
| 361 | // instr refers back to instr. (NB: quadratic) |
| 362 | switch val := val.(type) { |
| 363 | case *Const, *Global, *Builtin: |
| 364 | continue // not local |
| 365 | case *Function: |
| 366 | if val.parent == nil { |
| 367 | continue // only anon functions are local |
| 368 | } |
| 369 | } |
| 370 | |
| 371 | // TODO(adonovan): check val.Parent() != nil <=> val.Referrers() is defined. |
| 372 | |
| 373 | if refs := val.Referrers(); refs != nil { |
| 374 | for _, ref := range *refs { |
| 375 | if ref == instr { |
| 376 | continue operands |
| 377 | } |
| 378 | } |
| 379 | s.errorf("operand %d of %s (%s) does not refer to us", i, instr, val) |
| 380 | } else { |
| 381 | s.errorf("operand %d of %s (%s) has no referrers", i, instr, val) |
| 382 | } |
| 383 | } |
| 384 | } |
| 385 | } |
| 386 | |
| 387 | func (s *sanity) checkReferrerList(v Value) { |
| 388 | refs := v.Referrers() |
| 389 | if refs == nil { |
| 390 | s.errorf("%s has missing referrer list", v.Name()) |
| 391 | return |
| 392 | } |
| 393 | for i, ref := range *refs { |
| 394 | if _, ok := s.instrs[ref]; !ok { |
| 395 | s.errorf("%s.Referrers()[%d] = %s is not an instruction belonging to this function", v.Name(), i, ref) |
| 396 | } |
| 397 | } |
| 398 | } |
| 399 | |
| 400 | func (s *sanity) checkFunction(fn *Function) bool { |
| 401 | // TODO(adonovan): check Function invariants: |
| 402 | // - check params match signature |
| 403 | // - check transient fields are nil |
| 404 | // - warn if any fn.Locals do not appear among block instructions. |
| 405 | |
| 406 | // TODO(taking): Sanity check origin, typeparams, and typeargs. |
| 407 | s.fn = fn |
| 408 | if fn.Prog == nil { |
| 409 | s.errorf("nil Prog") |
| 410 | } |
| 411 | |
| 412 | _ = fn.String() // must not crash |
| 413 | _ = fn.RelString(fn.relPkg()) // must not crash |
| 414 | |
| 415 | // All functions have a package, except delegates (which are |
| 416 | // shared across packages, or duplicated as weak symbols in a |
| 417 | // separate-compilation model), and error.Error. |
| 418 | if fn.Pkg == nil { |
| 419 | if strings.HasPrefix(fn.Synthetic, "wrapper ") || |
| 420 | strings.HasPrefix(fn.Synthetic, "bound ") || |
| 421 | strings.HasPrefix(fn.Synthetic, "thunk ") || |
| 422 | strings.HasSuffix(fn.name, "Error") || |
| 423 | strings.HasPrefix(fn.Synthetic, "instance ") || |
| 424 | strings.HasPrefix(fn.Synthetic, "instantiation ") || |
| 425 | (fn.parent != nil && len(fn.typeargs) > 0) /* anon fun in instance */ { |
| 426 | // ok |
| 427 | } else { |
| 428 | s.errorf("nil Pkg") |
| 429 | } |
| 430 | } |
| 431 | if src, syn := fn.Synthetic == "", fn.Syntax() != nil; src != syn { |
| 432 | if len(fn.typeargs) > 0 && fn.Prog.mode&InstantiateGenerics != 0 { |
| 433 | // ok (instantiation with InstantiateGenerics on) |
| 434 | } else if fn.topLevelOrigin != nil && len(fn.typeargs) > 0 { |
| 435 | // ok (we always have the syntax set for instantiation) |
| 436 | } else { |
| 437 | s.errorf("got fromSource=%t, hasSyntax=%t; want same values", src, syn) |
| 438 | } |
| 439 | } |
| 440 | for i, l := range fn.Locals { |
| 441 | if l.Parent() != fn { |
| 442 | s.errorf("Local %s at index %d has wrong parent", l.Name(), i) |
| 443 | } |
| 444 | if l.Heap { |
| 445 | s.errorf("Local %s at index %d has Heap flag set", l.Name(), i) |
| 446 | } |
| 447 | } |
| 448 | // Build the set of valid referrers. |
| 449 | s.instrs = make(map[Instruction]struct{}) |
| 450 | for _, b := range fn.Blocks { |
| 451 | for _, instr := range b.Instrs { |
| 452 | s.instrs[instr] = struct{}{} |
| 453 | } |
| 454 | } |
| 455 | for i, p := range fn.Params { |
| 456 | if p.Parent() != fn { |
| 457 | s.errorf("Param %s at index %d has wrong parent", p.Name(), i) |
| 458 | } |
| 459 | // Check common suffix of Signature and Params match type. |
| 460 | if sig := fn.Signature; sig != nil { |
| 461 | j := i - len(fn.Params) + sig.Params().Len() // index within sig.Params |
| 462 | if j < 0 { |
| 463 | continue |
| 464 | } |
| 465 | if !types.Identical(p.Type(), sig.Params().At(j).Type()) { |
| 466 | 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()) |
| 467 | |
| 468 | } |
| 469 | } |
| 470 | s.checkReferrerList(p) |
| 471 | } |
| 472 | for i, fv := range fn.FreeVars { |
| 473 | if fv.Parent() != fn { |
| 474 | s.errorf("FreeVar %s at index %d has wrong parent", fv.Name(), i) |
| 475 | } |
| 476 | s.checkReferrerList(fv) |
| 477 | } |
| 478 | |
| 479 | if fn.Blocks != nil && len(fn.Blocks) == 0 { |
| 480 | // Function _had_ blocks (so it's not external) but |
| 481 | // they were "optimized" away, even the entry block. |
| 482 | s.errorf("Blocks slice is non-nil but empty") |
| 483 | } |
| 484 | for i, b := range fn.Blocks { |
| 485 | if b == nil { |
| 486 | s.warnf("nil *BasicBlock at f.Blocks[%d]", i) |
| 487 | continue |
| 488 | } |
| 489 | s.checkBlock(b, i) |
| 490 | } |
| 491 | if fn.Recover != nil && fn.Blocks[fn.Recover.Index] != fn.Recover { |
| 492 | s.errorf("Recover block is not in Blocks slice") |
| 493 | } |
| 494 | |
| 495 | s.block = nil |
| 496 | for i, anon := range fn.AnonFuncs { |
| 497 | if anon.Parent() != fn { |
| 498 | s.errorf("AnonFuncs[%d]=%s but %s.Parent()=%s", i, anon, anon, anon.Parent()) |
| 499 | } |
| 500 | if i != int(anon.anonIdx) { |
| 501 | s.errorf("AnonFuncs[%d]=%s but %s.anonIdx=%d", i, anon, anon, anon.anonIdx) |
| 502 | } |
| 503 | } |
| 504 | s.fn = nil |
| 505 | return !s.insane |
| 506 | } |
| 507 | |
| 508 | // sanityCheckPackage checks invariants of packages upon creation. |
| 509 | // It does not require that the package is built. |
| 510 | // Unlike sanityCheck (for functions), it just panics at the first error. |
| 511 | func sanityCheckPackage(pkg *Package) { |
| 512 | if pkg.Pkg == nil { |
| 513 | panic(fmt.Sprintf("Package %s has no Object", pkg)) |
| 514 | } |
| 515 | _ = pkg.String() // must not crash |
| 516 | |
| 517 | for name, mem := range pkg.Members { |
| 518 | if name != mem.Name() { |
| 519 | panic(fmt.Sprintf("%s: %T.Name() = %s, want %s", |
| 520 | pkg.Pkg.Path(), mem, mem.Name(), name)) |
| 521 | } |
| 522 | obj := mem.Object() |
| 523 | if obj == nil { |
| 524 | // This check is sound because fields |
| 525 | // {Global,Function}.object have type |
| 526 | // types.Object. (If they were declared as |
| 527 | // *types.{Var,Func}, we'd have a non-empty |
| 528 | // interface containing a nil pointer.) |
| 529 | |
| 530 | continue // not all members have typechecker objects |
| 531 | } |
| 532 | if obj.Name() != name { |
| 533 | if obj.Name() == "init" && strings.HasPrefix(mem.Name(), "init#") { |
| 534 | // Ok. The name of a declared init function varies between |
| 535 | // its types.Func ("init") and its ssa.Function ("init#%d"). |
| 536 | } else { |
| 537 | panic(fmt.Sprintf("%s: %T.Object().Name() = %s, want %s", |
| 538 | pkg.Pkg.Path(), mem, obj.Name(), name)) |
| 539 | } |
| 540 | } |
| 541 | if obj.Pos() != mem.Pos() { |
| 542 | panic(fmt.Sprintf("%s Pos=%d obj.Pos=%d", mem, mem.Pos(), obj.Pos())) |
| 543 | } |
| 544 | } |
| 545 | } |
| 546 |
Members