--- /dev/null
+// 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"
+ "go/types"
+ "io"
+ "os"
+ "strings"
+)
+
+type sanity struct {
+ reporter io.Writer
+ fn *Function
+ block *BasicBlock
+ instrs map[Instruction]struct{}
+ 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.WriteTo(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, *Return, *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))
+ }
+
+ if call, ok := instr.(CallInstruction); ok {
+ if call.Common().Signature() == nil {
+ s.errorf("nil signature: %s", call)
+ }
+ }
+
+ // Check that value-defining instructions have valid types
+ // and a valid referrer list.
+ 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)
+ }
+ s.checkReferrerList(v)
+ }
+
+ // Untyped constants are legal as instruction Operands(),
+ // for example:
+ // _ = "foo"[0]
+ // or:
+ // if wordsize==64 {...}
+
+ // All other non-Instruction Values can be found via their
+ // enclosing Function or Package.
+}
+
+func (s *sanity) checkFinalInstr(instr Instruction) {
+ switch instr := 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 *Return:
+ if nsuccs := len(s.block.Succs); nsuccs != 0 {
+ s.errorf("Return-terminated block has %d successors; expected none", nsuccs)
+ return
+ }
+ if na, nf := len(instr.Results), s.fn.Signature.Results().Len(); nf != na {
+ s.errorf("%d-ary return in %d-ary function", na, nf)
+ }
+
+ 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,
+ // as is the Recover block, if any.)
+ if (index > 0 && b != b.parent.Recover) && 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.
+ n := len(b.Instrs)
+ if n == 0 {
+ s.errorf("basic block contains no instructions")
+ }
+ var rands [10]*Value // reuse storage
+ 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(instr)
+ }
+
+ // Check Instruction.Operands.
+ operands:
+ for i, op := range instr.Operands(rands[:0]) {
+ if op == nil {
+ s.errorf("nil operand pointer %d of %s", i, instr)
+ continue
+ }
+ val := *op
+ if val == nil {
+ continue // a nil operand is ok
+ }
+
+ // Check that "untyped" types only appear on constant operands.
+ if _, ok := (*op).(*Const); !ok {
+ if basic, ok := (*op).Type().(*types.Basic); ok {
+ if basic.Info()&types.IsUntyped != 0 {
+ s.errorf("operand #%d of %s is untyped: %s", i, instr, basic)
+ }
+ }
+ }
+
+ // Check that Operands that are also Instructions belong to same function.
+ // TODO(adonovan): also check their block dominates block b.
+ if val, ok := val.(Instruction); ok {
+ if val.Block() == nil {
+ s.errorf("operand %d of %s is an instruction (%s) that belongs to no block", i, instr, val)
+ } else if val.Parent() != s.fn {
+ s.errorf("operand %d of %s is an instruction (%s) from function %s", i, instr, val, val.Parent())
+ }
+ }
+
+ // Check that each function-local operand of
+ // instr refers back to instr. (NB: quadratic)
+ switch val := val.(type) {
+ case *Const, *Global, *Builtin:
+ continue // not local
+ case *Function:
+ if val.parent == nil {
+ continue // only anon functions are local
+ }
+ }
+
+ // TODO(adonovan): check val.Parent() != nil <=> val.Referrers() is defined.
+
+ if refs := val.Referrers(); refs != nil {
+ for _, ref := range *refs {
+ if ref == instr {
+ continue operands
+ }
+ }
+ s.errorf("operand %d of %s (%s) does not refer to us", i, instr, val)
+ } else {
+ s.errorf("operand %d of %s (%s) has no referrers", i, instr, val)
+ }
+ }
+ }
+}
+
+func (s *sanity) checkReferrerList(v Value) {
+ refs := v.Referrers()
+ if refs == nil {
+ s.errorf("%s has missing referrer list", v.Name())
+ return
+ }
+ for i, ref := range *refs {
+ if _, ok := s.instrs[ref]; !ok {
+ s.errorf("%s.Referrers()[%d] = %s is not an instruction belonging to this function", v.Name(), i, ref)
+ }
+ }
+}
+
+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")
+ }
+
+ _ = fn.String() // must not crash
+ _ = fn.RelString(fn.pkg()) // must not crash
+
+ // All functions have a package, except delegates (which are
+ // shared across packages, or duplicated as weak symbols in a
+ // separate-compilation model), and error.Error.
+ if fn.Pkg == nil {
+ if strings.HasPrefix(fn.Synthetic, "wrapper ") ||
+ strings.HasPrefix(fn.Synthetic, "bound ") ||
+ strings.HasPrefix(fn.Synthetic, "thunk ") ||
+ strings.HasSuffix(fn.name, "Error") {
+ // ok
+ } else {
+ s.errorf("nil Pkg")
+ }
+ }
+ if src, syn := fn.Synthetic == "", fn.Syntax() != nil; src != syn {
+ s.errorf("got fromSource=%t, hasSyntax=%t; want same values", src, syn)
+ }
+ 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)
+ }
+ }
+ // Build the set of valid referrers.
+ s.instrs = make(map[Instruction]struct{})
+ for _, b := range fn.Blocks {
+ for _, instr := range b.Instrs {
+ s.instrs[instr] = struct{}{}
+ }
+ }
+ for i, p := range fn.Params {
+ if p.Parent() != fn {
+ s.errorf("Param %s at index %d has wrong parent", p.Name(), i)
+ }
+ // Check common suffix of Signature and Params match type.
+ if sig := fn.Signature; sig != nil {
+ j := i - len(fn.Params) + sig.Params().Len() // index within sig.Params
+ if j < 0 {
+ continue
+ }
+ if !types.Identical(p.Type(), sig.Params().At(j).Type()) {
+ 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())
+
+ }
+ }
+ s.checkReferrerList(p)
+ }
+ for i, fv := range fn.FreeVars {
+ if fv.Parent() != fn {
+ s.errorf("FreeVar %s at index %d has wrong parent", fv.Name(), i)
+ }
+ s.checkReferrerList(fv)
+ }
+
+ 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)
+ }
+ if fn.Recover != nil && fn.Blocks[fn.Recover.Index] != fn.Recover {
+ s.errorf("Recover block is not in Blocks slice")
+ }
+
+ s.block = nil
+ for i, anon := range fn.AnonFuncs {
+ if anon.Parent() != fn {
+ s.errorf("AnonFuncs[%d]=%s but %s.Parent()=%s", i, anon, anon, anon.Parent())
+ }
+ }
+ 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) {
+ if pkg.Pkg == nil {
+ panic(fmt.Sprintf("Package %s has no Object", pkg))
+ }
+ _ = pkg.String() // must not crash
+
+ for name, mem := range pkg.Members {
+ if name != mem.Name() {
+ panic(fmt.Sprintf("%s: %T.Name() = %s, want %s",
+ pkg.Pkg.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 {
+ if obj.Name() == "init" && strings.HasPrefix(mem.Name(), "init#") {
+ // Ok. The name of a declared init function varies between
+ // its types.Func ("init") and its ssa.Function ("init#%d").
+ } else {
+ panic(fmt.Sprintf("%s: %T.Object().Name() = %s, want %s",
+ pkg.Pkg.Path(), mem, obj.Name(), name))
+ }
+ }
+ if obj.Pos() != mem.Pos() {
+ panic(fmt.Sprintf("%s Pos=%d obj.Pos=%d", mem, mem.Pos(), obj.Pos()))
+ }
+ }
+}
projects / dotfiles / .git / blobdiff