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Diffstat (limited to 'vendor/golang.org/x/tools/go/ssa/builder.go')
| -rw-r--r-- | vendor/golang.org/x/tools/go/ssa/builder.go | 2379 |
1 files changed, 2379 insertions, 0 deletions
diff --git a/vendor/golang.org/x/tools/go/ssa/builder.go b/vendor/golang.org/x/tools/go/ssa/builder.go new file mode 100644 index 0000000..44abc5b --- /dev/null +++ b/vendor/golang.org/x/tools/go/ssa/builder.go @@ -0,0 +1,2379 @@ +// 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 + +// This file implements the BUILD phase of SSA construction. +// +// SSA construction has two phases, CREATE and BUILD. In the CREATE phase +// (create.go), all packages are constructed and type-checked and +// definitions of all package members are created, method-sets are +// computed, and wrapper methods are synthesized. +// ssa.Packages are created in arbitrary order. +// +// In the BUILD phase (builder.go), the builder traverses the AST of +// each Go source function and generates SSA instructions for the +// function body. Initializer expressions for package-level variables +// are emitted to the package's init() function in the order specified +// by go/types.Info.InitOrder, then code for each function in the +// package is generated in lexical order. +// The BUILD phases for distinct packages are independent and are +// executed in parallel. +// +// TODO(adonovan): indeed, building functions is now embarrassingly parallel. +// Audit for concurrency then benchmark using more goroutines. +// +// The builder's and Program's indices (maps) are populated and +// mutated during the CREATE phase, but during the BUILD phase they +// remain constant. The sole exception is Prog.methodSets and its +// related maps, which are protected by a dedicated mutex. + +import ( + "fmt" + "go/ast" + exact "go/constant" + "go/token" + "go/types" + "os" + "sync" +) + +type opaqueType struct { + types.Type + name string +} + +func (t *opaqueType) String() string { return t.name } + +var ( + varOk = newVar("ok", tBool) + varIndex = newVar("index", tInt) + + // Type constants. + tBool = types.Typ[types.Bool] + tByte = types.Typ[types.Byte] + tInt = types.Typ[types.Int] + tInvalid = types.Typ[types.Invalid] + tString = types.Typ[types.String] + tUntypedNil = types.Typ[types.UntypedNil] + tRangeIter = &opaqueType{nil, "iter"} // the type of all "range" iterators + tEface = types.NewInterface(nil, nil).Complete() + + // SSA Value constants. + vZero = intConst(0) + vOne = intConst(1) + vTrue = NewConst(exact.MakeBool(true), tBool) +) + +// builder holds state associated with the package currently being built. +// Its methods contain all the logic for AST-to-SSA conversion. +type builder struct{} + +// cond emits to fn code to evaluate boolean condition e and jump +// to t or f depending on its value, performing various simplifications. +// +// Postcondition: fn.currentBlock is nil. +// +func (b *builder) cond(fn *Function, e ast.Expr, t, f *BasicBlock) { + switch e := e.(type) { + case *ast.ParenExpr: + b.cond(fn, e.X, t, f) + return + + case *ast.BinaryExpr: + switch e.Op { + case token.LAND: + ltrue := fn.newBasicBlock("cond.true") + b.cond(fn, e.X, ltrue, f) + fn.currentBlock = ltrue + b.cond(fn, e.Y, t, f) + return + + case token.LOR: + lfalse := fn.newBasicBlock("cond.false") + b.cond(fn, e.X, t, lfalse) + fn.currentBlock = lfalse + b.cond(fn, e.Y, t, f) + return + } + + case *ast.UnaryExpr: + if e.Op == token.NOT { + b.cond(fn, e.X, f, t) + return + } + } + + // A traditional compiler would simplify "if false" (etc) here + // but we do not, for better fidelity to the source code. + // + // The value of a constant condition may be platform-specific, + // and may cause blocks that are reachable in some configuration + // to be hidden from subsequent analyses such as bug-finding tools. + emitIf(fn, b.expr(fn, e), t, f) +} + +// logicalBinop emits code to fn to evaluate e, a &&- or +// ||-expression whose reified boolean value is wanted. +// The value is returned. +// +func (b *builder) logicalBinop(fn *Function, e *ast.BinaryExpr) Value { + rhs := fn.newBasicBlock("binop.rhs") + done := fn.newBasicBlock("binop.done") + + // T(e) = T(e.X) = T(e.Y) after untyped constants have been + // eliminated. + // TODO(adonovan): not true; MyBool==MyBool yields UntypedBool. + t := fn.Pkg.typeOf(e) + + var short Value // value of the short-circuit path + switch e.Op { + case token.LAND: + b.cond(fn, e.X, rhs, done) + short = NewConst(exact.MakeBool(false), t) + + case token.LOR: + b.cond(fn, e.X, done, rhs) + short = NewConst(exact.MakeBool(true), t) + } + + // Is rhs unreachable? + if rhs.Preds == nil { + // Simplify false&&y to false, true||y to true. + fn.currentBlock = done + return short + } + + // Is done unreachable? + if done.Preds == nil { + // Simplify true&&y (or false||y) to y. + fn.currentBlock = rhs + return b.expr(fn, e.Y) + } + + // All edges from e.X to done carry the short-circuit value. + var edges []Value + for range done.Preds { + edges = append(edges, short) + } + + // The edge from e.Y to done carries the value of e.Y. + fn.currentBlock = rhs + edges = append(edges, b.expr(fn, e.Y)) + emitJump(fn, done) + fn.currentBlock = done + + phi := &Phi{Edges: edges, Comment: e.Op.String()} + phi.pos = e.OpPos + phi.typ = t + return done.emit(phi) +} + +// exprN lowers a multi-result expression e to SSA form, emitting code +// to fn and returning a single Value whose type is a *types.Tuple. +// The caller must access the components via Extract. +// +// Multi-result expressions include CallExprs in a multi-value +// assignment or return statement, and "value,ok" uses of +// TypeAssertExpr, IndexExpr (when X is a map), and UnaryExpr (when Op +// is token.ARROW). +// +func (b *builder) exprN(fn *Function, e ast.Expr) Value { + typ := fn.Pkg.typeOf(e).(*types.Tuple) + switch e := e.(type) { + case *ast.ParenExpr: + return b.exprN(fn, e.X) + + case *ast.CallExpr: + // Currently, no built-in function nor type conversion + // has multiple results, so we can avoid some of the + // cases for single-valued CallExpr. + var c Call + b.setCall(fn, e, &c.Call) + c.typ = typ + return fn.emit(&c) + + case *ast.IndexExpr: + mapt := fn.Pkg.typeOf(e.X).Underlying().(*types.Map) + lookup := &Lookup{ + X: b.expr(fn, e.X), + Index: emitConv(fn, b.expr(fn, e.Index), mapt.Key()), + CommaOk: true, + } + lookup.setType(typ) + lookup.setPos(e.Lbrack) + return fn.emit(lookup) + + case *ast.TypeAssertExpr: + return emitTypeTest(fn, b.expr(fn, e.X), typ.At(0).Type(), e.Lparen) + + case *ast.UnaryExpr: // must be receive <- + unop := &UnOp{ + Op: token.ARROW, + X: b.expr(fn, e.X), + CommaOk: true, + } + unop.setType(typ) + unop.setPos(e.OpPos) + return fn.emit(unop) + } + panic(fmt.Sprintf("exprN(%T) in %s", e, fn)) +} + +// builtin emits to fn SSA instructions to implement a call to the +// built-in function obj with the specified arguments +// and return type. It returns the value defined by the result. +// +// The result is nil if no special handling was required; in this case +// the caller should treat this like an ordinary library function +// call. +// +func (b *builder) builtin(fn *Function, obj *types.Builtin, args []ast.Expr, typ types.Type, pos token.Pos) Value { + switch obj.Name() { + case "make": + switch typ.Underlying().(type) { + case *types.Slice: + n := b.expr(fn, args[1]) + m := n + if len(args) == 3 { + m = b.expr(fn, args[2]) + } + if m, ok := m.(*Const); ok { + // treat make([]T, n, m) as new([m]T)[:n] + cap := m.Int64() + at := types.NewArray(typ.Underlying().(*types.Slice).Elem(), cap) + alloc := emitNew(fn, at, pos) + alloc.Comment = "makeslice" + v := &Slice{ + X: alloc, + High: n, + } + v.setPos(pos) + v.setType(typ) + return fn.emit(v) + } + v := &MakeSlice{ + Len: n, + Cap: m, + } + v.setPos(pos) + v.setType(typ) + return fn.emit(v) + + case *types.Map: + var res Value + if len(args) == 2 { + res = b.expr(fn, args[1]) + } + v := &MakeMap{Reserve: res} + v.setPos(pos) + v.setType(typ) + return fn.emit(v) + + case *types.Chan: + var sz Value = vZero + if len(args) == 2 { + sz = b.expr(fn, args[1]) + } + v := &MakeChan{Size: sz} + v.setPos(pos) + v.setType(typ) + return fn.emit(v) + } + + case "new": + alloc := emitNew(fn, deref(typ), pos) + alloc.Comment = "new" + return alloc + + case "len", "cap": + // Special case: len or cap of an array or *array is + // based on the type, not the value which may be nil. + // We must still evaluate the value, though. (If it + // was side-effect free, the whole call would have + // been constant-folded.) + t := deref(fn.Pkg.typeOf(args[0])).Underlying() + if at, ok := t.(*types.Array); ok { + b.expr(fn, args[0]) // for effects only + return intConst(at.Len()) + } + // Otherwise treat as normal. + + case "panic": + fn.emit(&Panic{ + X: emitConv(fn, b.expr(fn, args[0]), tEface), + pos: pos, + }) + fn.currentBlock = fn.newBasicBlock("unreachable") + return vTrue // any non-nil Value will do + } + return nil // treat all others as a regular function call +} + +// addr lowers a single-result addressable expression e to SSA form, +// emitting code to fn and returning the location (an lvalue) defined +// by the expression. +// +// If escaping is true, addr marks the base variable of the +// addressable expression e as being a potentially escaping pointer +// value. For example, in this code: +// +// a := A{ +// b: [1]B{B{c: 1}} +// } +// return &a.b[0].c +// +// the application of & causes a.b[0].c to have its address taken, +// which means that ultimately the local variable a must be +// heap-allocated. This is a simple but very conservative escape +// analysis. +// +// Operations forming potentially escaping pointers include: +// - &x, including when implicit in method call or composite literals. +// - a[:] iff a is an array (not *array) +// - references to variables in lexically enclosing functions. +// +func (b *builder) addr(fn *Function, e ast.Expr, escaping bool) lvalue { + switch e := e.(type) { + case *ast.Ident: + if isBlankIdent(e) { + return blank{} + } + obj := fn.Pkg.objectOf(e) + v := fn.Prog.packageLevelValue(obj) // var (address) + if v == nil { + v = fn.lookup(obj, escaping) + } + return &address{addr: v, pos: e.Pos(), expr: e} + + case *ast.CompositeLit: + t := deref(fn.Pkg.typeOf(e)) + var v *Alloc + if escaping { + v = emitNew(fn, t, e.Lbrace) + } else { + v = fn.addLocal(t, e.Lbrace) + } + v.Comment = "complit" + var sb storebuf + b.compLit(fn, v, e, true, &sb) + sb.emit(fn) + return &address{addr: v, pos: e.Lbrace, expr: e} + + case *ast.ParenExpr: + return b.addr(fn, e.X, escaping) + + case *ast.SelectorExpr: + sel, ok := fn.Pkg.info.Selections[e] + if !ok { + // qualified identifier + return b.addr(fn, e.Sel, escaping) + } + if sel.Kind() != types.FieldVal { + panic(sel) + } + wantAddr := true + v := b.receiver(fn, e.X, wantAddr, escaping, sel) + last := len(sel.Index()) - 1 + return &address{ + addr: emitFieldSelection(fn, v, sel.Index()[last], true, e.Sel), + pos: e.Sel.Pos(), + expr: e.Sel, + } + + case *ast.IndexExpr: + var x Value + var et types.Type + switch t := fn.Pkg.typeOf(e.X).Underlying().(type) { + case *types.Array: + x = b.addr(fn, e.X, escaping).address(fn) + et = types.NewPointer(t.Elem()) + case *types.Pointer: // *array + x = b.expr(fn, e.X) + et = types.NewPointer(t.Elem().Underlying().(*types.Array).Elem()) + case *types.Slice: + x = b.expr(fn, e.X) + et = types.NewPointer(t.Elem()) + case *types.Map: + return &element{ + m: b.expr(fn, e.X), + k: emitConv(fn, b.expr(fn, e.Index), t.Key()), + t: t.Elem(), + pos: e.Lbrack, + } + default: + panic("unexpected container type in IndexExpr: " + t.String()) + } + v := &IndexAddr{ + X: x, + Index: emitConv(fn, b.expr(fn, e.Index), tInt), + } + v.setPos(e.Lbrack) + v.setType(et) + return &address{addr: fn.emit(v), pos: e.Lbrack, expr: e} + + case *ast.StarExpr: + return &address{addr: b.expr(fn, e.X), pos: e.Star, expr: e} + } + + panic(fmt.Sprintf("unexpected address expression: %T", e)) +} + +type store struct { + lhs lvalue + rhs Value +} + +type storebuf struct{ stores []store } + +func (sb *storebuf) store(lhs lvalue, rhs Value) { + sb.stores = append(sb.stores, store{lhs, rhs}) +} + +func (sb *storebuf) emit(fn *Function) { + for _, s := range sb.stores { + s.lhs.store(fn, s.rhs) + } +} + +// assign emits to fn code to initialize the lvalue loc with the value +// of expression e. If isZero is true, assign assumes that loc holds +// the zero value for its type. +// +// This is equivalent to loc.store(fn, b.expr(fn, e)), but may generate +// better code in some cases, e.g., for composite literals in an +// addressable location. +// +// If sb is not nil, assign generates code to evaluate expression e, but +// not to update loc. Instead, the necessary stores are appended to the +// storebuf sb so that they can be executed later. This allows correct +// in-place update of existing variables when the RHS is a composite +// literal that may reference parts of the LHS. +// +func (b *builder) assign(fn *Function, loc lvalue, e ast.Expr, isZero bool, sb *storebuf) { + // Can we initialize it in place? + if e, ok := unparen(e).(*ast.CompositeLit); ok { + // A CompositeLit never evaluates to a pointer, + // so if the type of the location is a pointer, + // an &-operation is implied. + if _, ok := loc.(blank); !ok { // avoid calling blank.typ() + if isPointer(loc.typ()) { + ptr := b.addr(fn, e, true).address(fn) + // copy address + if sb != nil { + sb.store(loc, ptr) + } else { + loc.store(fn, ptr) + } + return + } + } + + if _, ok := loc.(*address); ok { + if isInterface(loc.typ()) { + // e.g. var x interface{} = T{...} + // Can't in-place initialize an interface value. + // Fall back to copying. + } else { + // x = T{...} or x := T{...} + addr := loc.address(fn) + if sb != nil { + b.compLit(fn, addr, e, isZero, sb) + } else { + var sb storebuf + b.compLit(fn, addr, e, isZero, &sb) + sb.emit(fn) + } + + // Subtle: emit debug ref for aggregate types only; + // slice and map are handled by store ops in compLit. + switch loc.typ().Underlying().(type) { + case *types.Struct, *types.Array: + emitDebugRef(fn, e, addr, true) + } + + return + } + } + } + + // simple case: just copy + rhs := b.expr(fn, e) + if sb != nil { + sb.store(loc, rhs) + } else { + loc.store(fn, rhs) + } +} + +// expr lowers a single-result expression e to SSA form, emitting code +// to fn and returning the Value defined by the expression. +// +func (b *builder) expr(fn *Function, e ast.Expr) Value { + e = unparen(e) + + tv := fn.Pkg.info.Types[e] + + // Is expression a constant? + if tv.Value != nil { + return NewConst(tv.Value, tv.Type) + } + + var v Value + if tv.Addressable() { + // Prefer pointer arithmetic ({Index,Field}Addr) followed + // by Load over subelement extraction (e.g. Index, Field), + // to avoid large copies. + v = b.addr(fn, e, false).load(fn) + } else { + v = b.expr0(fn, e, tv) + } + if fn.debugInfo() { + emitDebugRef(fn, e, v, false) + } + return v +} + +func (b *builder) expr0(fn *Function, e ast.Expr, tv types.TypeAndValue) Value { + switch e := e.(type) { + case *ast.BasicLit: + panic("non-constant BasicLit") // unreachable + + case *ast.FuncLit: + fn2 := &Function{ + name: fmt.Sprintf("%s$%d", fn.Name(), 1+len(fn.AnonFuncs)), + Signature: fn.Pkg.typeOf(e.Type).Underlying().(*types.Signature), + pos: e.Type.Func, + parent: fn, + Pkg: fn.Pkg, + Prog: fn.Prog, + syntax: e, + } + fn.AnonFuncs = append(fn.AnonFuncs, fn2) + b.buildFunction(fn2) + if fn2.FreeVars == nil { + return fn2 + } + v := &MakeClosure{Fn: fn2} + v.setType(tv.Type) + for _, fv := range fn2.FreeVars { + v.Bindings = append(v.Bindings, fv.outer) + fv.outer = nil + } + return fn.emit(v) + + case *ast.TypeAssertExpr: // single-result form only + return emitTypeAssert(fn, b.expr(fn, e.X), tv.Type, e.Lparen) + + case *ast.CallExpr: + if fn.Pkg.info.Types[e.Fun].IsType() { + // Explicit type conversion, e.g. string(x) or big.Int(x) + x := b.expr(fn, e.Args[0]) + y := emitConv(fn, x, tv.Type) + if y != x { + switch y := y.(type) { + case *Convert: + y.pos = e.Lparen + case *ChangeType: + y.pos = e.Lparen + case *MakeInterface: + y.pos = e.Lparen + } + } + return y + } + // Call to "intrinsic" built-ins, e.g. new, make, panic. + if id, ok := unparen(e.Fun).(*ast.Ident); ok { + if obj, ok := fn.Pkg.info.Uses[id].(*types.Builtin); ok { + if v := b.builtin(fn, obj, e.Args, tv.Type, e.Lparen); v != nil { + return v + } + } + } + // Regular function call. + var v Call + b.setCall(fn, e, &v.Call) + v.setType(tv.Type) + return fn.emit(&v) + + case *ast.UnaryExpr: + switch e.Op { + case token.AND: // &X --- potentially escaping. + addr := b.addr(fn, e.X, true) + if _, ok := unparen(e.X).(*ast.StarExpr); ok { + // &*p must panic if p is nil (http://golang.org/s/go12nil). + // For simplicity, we'll just (suboptimally) rely + // on the side effects of a load. + // TODO(adonovan): emit dedicated nilcheck. + addr.load(fn) + } + return addr.address(fn) + case token.ADD: + return b.expr(fn, e.X) + case token.NOT, token.ARROW, token.SUB, token.XOR: // ! <- - ^ + v := &UnOp{ + Op: e.Op, + X: b.expr(fn, e.X), + } + v.setPos(e.OpPos) + v.setType(tv.Type) + return fn.emit(v) + default: + panic(e.Op) + } + + case *ast.BinaryExpr: + switch e.Op { + case token.LAND, token.LOR: + return b.logicalBinop(fn, e) + case token.SHL, token.SHR: + fallthrough + case token.ADD, token.SUB, token.MUL, token.QUO, token.REM, token.AND, token.OR, token.XOR, token.AND_NOT: + return emitArith(fn, e.Op, b.expr(fn, e.X), b.expr(fn, e.Y), tv.Type, e.OpPos) + + case token.EQL, token.NEQ, token.GTR, token.LSS, token.LEQ, token.GEQ: + cmp := emitCompare(fn, e.Op, b.expr(fn, e.X), b.expr(fn, e.Y), e.OpPos) + // The type of x==y may be UntypedBool. + return emitConv(fn, cmp, DefaultType(tv.Type)) + default: + panic("illegal op in BinaryExpr: " + e.Op.String()) + } + + case *ast.SliceExpr: + var low, high, max Value + var x Value + switch fn.Pkg.typeOf(e.X).Underlying().(type) { + case *types.Array: + // Potentially escaping. + x = b.addr(fn, e.X, true).address(fn) + case *types.Basic, *types.Slice, *types.Pointer: // *array + x = b.expr(fn, e.X) + default: + panic("unreachable") + } + if e.High != nil { + high = b.expr(fn, e.High) + } + if e.Low != nil { + low = b.expr(fn, e.Low) + } + if e.Slice3 { + max = b.expr(fn, e.Max) + } + v := &Slice{ + X: x, + Low: low, + High: high, + Max: max, + } + v.setPos(e.Lbrack) + v.setType(tv.Type) + return fn.emit(v) + + case *ast.Ident: + obj := fn.Pkg.info.Uses[e] + // Universal built-in or nil? + switch obj := obj.(type) { + case *types.Builtin: + return &Builtin{name: obj.Name(), sig: tv.Type.(*types.Signature)} + case *types.Nil: + return nilConst(tv.Type) + } + // Package-level func or var? + if v := fn.Prog.packageLevelValue(obj); v != nil { + if _, ok := obj.(*types.Var); ok { + return emitLoad(fn, v) // var (address) + } + return v // (func) + } + // Local var. + return emitLoad(fn, fn.lookup(obj, false)) // var (address) + + case *ast.SelectorExpr: + sel, ok := fn.Pkg.info.Selections[e] + if !ok { + // qualified identifier + return b.expr(fn, e.Sel) + } + switch sel.Kind() { + case types.MethodExpr: + // (*T).f or T.f, the method f from the method-set of type T. + // The result is a "thunk". + return emitConv(fn, makeThunk(fn.Prog, sel), tv.Type) + + case types.MethodVal: + // e.f where e is an expression and f is a method. + // The result is a "bound". + obj := sel.Obj().(*types.Func) + rt := recvType(obj) + wantAddr := isPointer(rt) + escaping := true + v := b.receiver(fn, e.X, wantAddr, escaping, sel) + if isInterface(rt) { + // If v has interface type I, + // we must emit a check that v is non-nil. + // We use: typeassert v.(I). + emitTypeAssert(fn, v, rt, token.NoPos) + } + c := &MakeClosure{ + Fn: makeBound(fn.Prog, obj), + Bindings: []Value{v}, + } + c.setPos(e.Sel.Pos()) + c.setType(tv.Type) + return fn.emit(c) + + case types.FieldVal: + indices := sel.Index() + last := len(indices) - 1 + v := b.expr(fn, e.X) + v = emitImplicitSelections(fn, v, indices[:last]) + v = emitFieldSelection(fn, v, indices[last], false, e.Sel) + return v + } + + panic("unexpected expression-relative selector") + + case *ast.IndexExpr: + switch t := fn.Pkg.typeOf(e.X).Underlying().(type) { + case *types.Array: + // Non-addressable array (in a register). + v := &Index{ + X: b.expr(fn, e.X), + Index: emitConv(fn, b.expr(fn, e.Index), tInt), + } + v.setPos(e.Lbrack) + v.setType(t.Elem()) + return fn.emit(v) + + case *types.Map: + // Maps are not addressable. + mapt := fn.Pkg.typeOf(e.X).Underlying().(*types.Map) + v := &Lookup{ + X: b.expr(fn, e.X), + Index: emitConv(fn, b.expr(fn, e.Index), mapt.Key()), + } + v.setPos(e.Lbrack) + v.setType(mapt.Elem()) + return fn.emit(v) + + case *types.Basic: // => string + // Strings are not addressable. + v := &Lookup{ + X: b.expr(fn, e.X), + Index: b.expr(fn, e.Index), + } + v.setPos(e.Lbrack) + v.setType(tByte) + return fn.emit(v) + + case *types.Slice, *types.Pointer: // *array + // Addressable slice/array; use IndexAddr and Load. + return b.addr(fn, e, false).load(fn) + + default: + panic("unexpected container type in IndexExpr: " + t.String()) + } + + case *ast.CompositeLit, *ast.StarExpr: + // Addressable types (lvalues) + return b.addr(fn, e, false).load(fn) + } + + panic(fmt.Sprintf("unexpected expr: %T", e)) +} + +// stmtList emits to fn code for all statements in list. +func (b *builder) stmtList(fn *Function, list []ast.Stmt) { + for _, s := range list { + b.stmt(fn, s) + } +} + +// receiver emits to fn code for expression e in the "receiver" +// position of selection e.f (where f may be a field or a method) and +// returns the effective receiver after applying the implicit field +// selections of sel. +// +// wantAddr requests that the result is an an address. If +// !sel.Indirect(), this may require that e be built in addr() mode; it +// must thus be addressable. +// +// escaping is defined as per builder.addr(). +// +func (b *builder) receiver(fn *Function, e ast.Expr, wantAddr, escaping bool, sel *types.Selection) Value { + var v Value + if wantAddr && !sel.Indirect() && !isPointer(fn.Pkg.typeOf(e)) { + v = b.addr(fn, e, escaping).address(fn) + } else { + v = b.expr(fn, e) + } + + last := len(sel.Index()) - 1 + v = emitImplicitSelections(fn, v, sel.Index()[:last]) + if !wantAddr && isPointer(v.Type()) { + v = emitLoad(fn, v) + } + return v +} + +// setCallFunc populates the function parts of a CallCommon structure +// (Func, Method, Recv, Args[0]) based on the kind of invocation +// occurring in e. +// +func (b *builder) setCallFunc(fn *Function, e *ast.CallExpr, c *CallCommon) { + c.pos = e.Lparen + + // Is this a method call? + if selector, ok := unparen(e.Fun).(*ast.SelectorExpr); ok { + sel, ok := fn.Pkg.info.Selections[selector] + if ok && sel.Kind() == types.MethodVal { + obj := sel.Obj().(*types.Func) + recv := recvType(obj) + wantAddr := isPointer(recv) + escaping := true + v := b.receiver(fn, selector.X, wantAddr, escaping, sel) + if isInterface(recv) { + // Invoke-mode call. + c.Value = v + c.Method = obj + } else { + // "Call"-mode call. + c.Value = fn.Prog.declaredFunc(obj) + c.Args = append(c.Args, v) + } + return + } + + // sel.Kind()==MethodExpr indicates T.f() or (*T).f(): + // a statically dispatched call to the method f in the + // method-set of T or *T. T may be an interface. + // + // e.Fun would evaluate to a concrete method, interface + // wrapper function, or promotion wrapper. + // + // For now, we evaluate it in the usual way. + // + // TODO(adonovan): opt: inline expr() here, to make the + // call static and to avoid generation of wrappers. + // It's somewhat tricky as it may consume the first + // actual parameter if the call is "invoke" mode. + // + // Examples: + // type T struct{}; func (T) f() {} // "call" mode + // type T interface { f() } // "invoke" mode + // + // type S struct{ T } + // + // var s S + // S.f(s) + // (*S).f(&s) + // + // Suggested approach: + // - consume the first actual parameter expression + // and build it with b.expr(). + // - apply implicit field selections. + // - use MethodVal logic to populate fields of c. + } + + // Evaluate the function operand in the usual way. + c.Value = b.expr(fn, e.Fun) +} + +// emitCallArgs emits to f code for the actual parameters of call e to +// a (possibly built-in) function of effective type sig. +// The argument values are appended to args, which is then returned. +// +func (b *builder) emitCallArgs(fn *Function, sig *types.Signature, e *ast.CallExpr, args []Value) []Value { + // f(x, y, z...): pass slice z straight through. + if e.Ellipsis != 0 { + for i, arg := range e.Args { + v := emitConv(fn, b.expr(fn, arg), sig.Params().At(i).Type()) + args = append(args, v) + } + return args + } + + offset := len(args) // 1 if call has receiver, 0 otherwise + + // Evaluate actual parameter expressions. + // + // If this is a chained call of the form f(g()) where g has + // multiple return values (MRV), they are flattened out into + // args; a suffix of them may end up in a varargs slice. + for _, arg := range e.Args { + v := b.expr(fn, arg) + if ttuple, ok := v.Type().(*types.Tuple); ok { // MRV chain + for i, n := 0, ttuple.Len(); i < n; i++ { + args = append(args, emitExtract(fn, v, i)) + } + } else { + args = append(args, v) + } + } + + // Actual->formal assignability conversions for normal parameters. + np := sig.Params().Len() // number of normal parameters + if sig.Variadic() { + np-- + } + for i := 0; i < np; i++ { + args[offset+i] = emitConv(fn, args[offset+i], sig.Params().At(i).Type()) + } + + // Actual->formal assignability conversions for variadic parameter, + // and construction of slice. + if sig.Variadic() { + varargs := args[offset+np:] + st := sig.Params().At(np).Type().(*types.Slice) + vt := st.Elem() + if len(varargs) == 0 { + args = append(args, nilConst(st)) + } else { + // Replace a suffix of args with a slice containing it. + at := types.NewArray(vt, int64(len(varargs))) + a := emitNew(fn, at, token.NoPos) + a.setPos(e.Rparen) + a.Comment = "varargs" + for i, arg := range varargs { + iaddr := &IndexAddr{ + X: a, + Index: intConst(int64(i)), + } + iaddr.setType(types.NewPointer(vt)) + fn.emit(iaddr) + emitStore(fn, iaddr, arg, arg.Pos()) + } + s := &Slice{X: a} + s.setType(st) + args[offset+np] = fn.emit(s) + args = args[:offset+np+1] + } + } + return args +} + +// setCall emits to fn code to evaluate all the parameters of a function +// call e, and populates *c with those values. +// +func (b *builder) setCall(fn *Function, e *ast.CallExpr, c *CallCommon) { + // First deal with the f(...) part and optional receiver. + b.setCallFunc(fn, e, c) + + // Then append the other actual parameters. + sig, _ := fn.Pkg.typeOf(e.Fun).Underlying().(*types.Signature) + if sig == nil { + panic(fmt.Sprintf("no signature for call of %s", e.Fun)) + } + c.Args = b.emitCallArgs(fn, sig, e, c.Args) +} + +// assignOp emits to fn code to perform loc += incr or loc -= incr. +func (b *builder) assignOp(fn *Function, loc lvalue, incr Value, op token.Token) { + oldv := loc.load(fn) + loc.store(fn, emitArith(fn, op, oldv, emitConv(fn, incr, oldv.Type()), loc.typ(), token.NoPos)) +} + +// localValueSpec emits to fn code to define all of the vars in the +// function-local ValueSpec, spec. +// +func (b *builder) localValueSpec(fn *Function, spec *ast.ValueSpec) { + switch { + case len(spec.Values) == len(spec.Names): + // e.g. var x, y = 0, 1 + // 1:1 assignment + for i, id := range spec.Names { + if !isBlankIdent(id) { + fn.addLocalForIdent(id) + } + lval := b.addr(fn, id, false) // non-escaping + b.assign(fn, lval, spec.Values[i], true, nil) + } + + case len(spec.Values) == 0: + // e.g. var x, y int + // Locals are implicitly zero-initialized. + for _, id := range spec.Names { + if !isBlankIdent(id) { + lhs := fn.addLocalForIdent(id) + if fn.debugInfo() { + emitDebugRef(fn, id, lhs, true) + } + } + } + + default: + // e.g. var x, y = pos() + tuple := b.exprN(fn, spec.Values[0]) + for i, id := range spec.Names { + if !isBlankIdent(id) { + fn.addLocalForIdent(id) + lhs := b.addr(fn, id, false) // non-escaping + lhs.store(fn, emitExtract(fn, tuple, i)) + } + } + } +} + +// assignStmt emits code to fn for a parallel assignment of rhss to lhss. +// isDef is true if this is a short variable declaration (:=). +// +// Note the similarity with localValueSpec. +// +func (b *builder) assignStmt(fn *Function, lhss, rhss []ast.Expr, isDef bool) { + // Side effects of all LHSs and RHSs must occur in left-to-right order. + lvals := make([]lvalue, len(lhss)) + isZero := make([]bool, len(lhss)) + for i, lhs := range lhss { + var lval lvalue = blank{} + if !isBlankIdent(lhs) { + if isDef { + if obj := fn.Pkg.info.Defs[lhs.(*ast.Ident)]; obj != nil { + fn.addNamedLocal(obj) + isZero[i] = true + } + } + lval = b.addr(fn, lhs, false) // non-escaping + } + lvals[i] = lval + } + if len(lhss) == len(rhss) { + // Simple assignment: x = f() (!isDef) + // Parallel assignment: x, y = f(), g() (!isDef) + // or short var decl: x, y := f(), g() (isDef) + // + // In all cases, the RHSs may refer to the LHSs, + // so we need a storebuf. + var sb storebuf + for i := range rhss { + b.assign(fn, lvals[i], rhss[i], isZero[i], &sb) + } + sb.emit(fn) + } else { + // e.g. x, y = pos() + tuple := b.exprN(fn, rhss[0]) + emitDebugRef(fn, rhss[0], tuple, false) + for i, lval := range lvals { + lval.store(fn, emitExtract(fn, tuple, i)) + } + } +} + +// arrayLen returns the length of the array whose composite literal elements are elts. +func (b *builder) arrayLen(fn *Function, elts []ast.Expr) int64 { + var max int64 = -1 + var i int64 = -1 + for _, e := range elts { + if kv, ok := e.(*ast.KeyValueExpr); ok { + i = b.expr(fn, kv.Key).(*Const).Int64() + } else { + i++ + } + if i > max { + max = i + } + } + return max + 1 +} + +// compLit emits to fn code to initialize a composite literal e at +// address addr with type typ. +// +// Nested composite literals are recursively initialized in place +// where possible. If isZero is true, compLit assumes that addr +// holds the zero value for typ. +// +// Because the elements of a composite literal may refer to the +// variables being updated, as in the second line below, +// x := T{a: 1} +// x = T{a: x.a} +// all the reads must occur before all the writes. Thus all stores to +// loc are emitted to the storebuf sb for later execution. +// +// A CompositeLit may have pointer type only in the recursive (nested) +// case when the type name is implicit. e.g. in []*T{{}}, the inner +// literal has type *T behaves like &T{}. +// In that case, addr must hold a T, not a *T. +// +func (b *builder) compLit(fn *Function, addr Value, e *ast.CompositeLit, isZero bool, sb *storebuf) { + typ := deref(fn.Pkg.typeOf(e)) + switch t := typ.Underlying().(type) { + case *types.Struct: + if !isZero && len(e.Elts) != t.NumFields() { + // memclear + sb.store(&address{addr, e.Lbrace, nil}, + zeroValue(fn, deref(addr.Type()))) + isZero = true + } + for i, e := range e.Elts { + fieldIndex := i + pos := e.Pos() + if kv, ok := e.(*ast.KeyValueExpr); ok { + fname := kv.Key.(*ast.Ident).Name + for i, n := 0, t.NumFields(); i < n; i++ { + sf := t.Field(i) + if sf.Name() == fname { + fieldIndex = i + pos = kv.Colon + e = kv.Value + break + } + } + } + sf := t.Field(fieldIndex) + faddr := &FieldAddr{ + X: addr, + Field: fieldIndex, + } + faddr.setType(types.NewPointer(sf.Type())) + fn.emit(faddr) + b.assign(fn, &address{addr: faddr, pos: pos, expr: e}, e, isZero, sb) + } + + case *types.Array, *types.Slice: + var at *types.Array + var array Value + switch t := t.(type) { + case *types.Slice: + at = types.NewArray(t.Elem(), b.arrayLen(fn, e.Elts)) + alloc := emitNew(fn, at, e.Lbrace) + alloc.Comment = "slicelit" + array = alloc + case *types.Array: + at = t + array = addr + + if !isZero && int64(len(e.Elts)) != at.Len() { + // memclear + sb.store(&address{array, e.Lbrace, nil}, + zeroValue(fn, deref(array.Type()))) + } + } + + var idx *Const + for _, e := range e.Elts { + pos := e.Pos() + if kv, ok := e.(*ast.KeyValueExpr); ok { + idx = b.expr(fn, kv.Key).(*Const) + pos = kv.Colon + e = kv.Value + } else { + var idxval int64 + if idx != nil { + idxval = idx.Int64() + 1 + } + idx = intConst(idxval) + } + iaddr := &IndexAddr{ + X: array, + Index: idx, + } + iaddr.setType(types.NewPointer(at.Elem())) + fn.emit(iaddr) + if t != at { // slice + // backing array is unaliased => storebuf not needed. + b.assign(fn, &address{addr: iaddr, pos: pos, expr: e}, e, true, nil) + } else { + b.assign(fn, &address{addr: iaddr, pos: pos, expr: e}, e, true, sb) + } + } + + if t != at { // slice + s := &Slice{X: array} + s.setPos(e.Lbrace) + s.setType(typ) + sb.store(&address{addr: addr, pos: e.Lbrace, expr: e}, fn.emit(s)) + } + + case *types.Map: + m := &MakeMap{Reserve: intConst(int64(len(e.Elts)))} + m.setPos(e.Lbrace) + m.setType(typ) + fn.emit(m) + for _, e := range e.Elts { + e := e.(*ast.KeyValueExpr) + + // If a key expression in a map literal is itself a + // composite literal, the type may be omitted. + // For example: + // map[*struct{}]bool{{}: true} + // An &-operation may be implied: + // map[*struct{}]bool{&struct{}{}: true} + var key Value + if _, ok := unparen(e.Key).(*ast.CompositeLit); ok && isPointer(t.Key()) { + // A CompositeLit never evaluates to a pointer, + // so if the type of the location is a pointer, + // an &-operation is implied. + key = b.addr(fn, e.Key, true).address(fn) + } else { + key = b.expr(fn, e.Key) + } + + loc := element{ + m: m, + k: emitConv(fn, key, t.Key()), + t: t.Elem(), + pos: e.Colon, + } + + // We call assign() only because it takes care + // of any &-operation required in the recursive + // case, e.g., + // map[int]*struct{}{0: {}} implies &struct{}{}. + // In-place update is of course impossible, + // and no storebuf is needed. + b.assign(fn, &loc, e.Value, true, nil) + } + sb.store(&address{addr: addr, pos: e.Lbrace, expr: e}, m) + + default: + panic("unexpected CompositeLit type: " + t.String()) + } +} + +// switchStmt emits to fn code for the switch statement s, optionally +// labelled by label. +// +func (b *builder) switchStmt(fn *Function, s *ast.SwitchStmt, label *lblock) { + // We treat SwitchStmt like a sequential if-else chain. + // Multiway dispatch can be recovered later by ssautil.Switches() + // to those cases that are free of side effects. + if s.Init != nil { + b.stmt(fn, s.Init) + } + var tag Value = vTrue + if s.Tag != nil { + tag = b.expr(fn, s.Tag) + } + done := fn.newBasicBlock("switch.done") + if label != nil { + label._break = done + } + // We pull the default case (if present) down to the end. + // But each fallthrough label must point to the next + // body block in source order, so we preallocate a + // body block (fallthru) for the next case. + // Unfortunately this makes for a confusing block order. + var dfltBody *[]ast.Stmt + var dfltFallthrough *BasicBlock + var fallthru, dfltBlock *BasicBlock + ncases := len(s.Body.List) + for i, clause := range s.Body.List { + body := fallthru + if body == nil { + body = fn.newBasicBlock("switch.body") // first case only + } + + // Preallocate body block for the next case. + fallthru = done + if i+1 < ncases { + fallthru = fn.newBasicBlock("switch.body") + } + + cc := clause.(*ast.CaseClause) + if cc.List == nil { + // Default case. + dfltBody = &cc.Body + dfltFallthrough = fallthru + dfltBlock = body + continue + } + + var nextCond *BasicBlock + for _, cond := range cc.List { + nextCond = fn.newBasicBlock("switch.next") + // TODO(adonovan): opt: when tag==vTrue, we'd + // get better code if we use b.cond(cond) + // instead of BinOp(EQL, tag, b.expr(cond)) + // followed by If. Don't forget conversions + // though. + cond := emitCompare(fn, token.EQL, tag, b.expr(fn, cond), token.NoPos) + emitIf(fn, cond, body, nextCond) + fn.currentBlock = nextCond + } + fn.currentBlock = body + fn.targets = &targets{ + tail: fn.targets, + _break: done, + _fallthrough: fallthru, + } + b.stmtList(fn, cc.Body) + fn.targets = fn.targets.tail + emitJump(fn, done) + fn.currentBlock = nextCond + } + if dfltBlock != nil { + emitJump(fn, dfltBlock) + fn.currentBlock = dfltBlock + fn.targets = &targets{ + tail: fn.targets, + _break: done, + _fallthrough: dfltFallthrough, + } + b.stmtList(fn, *dfltBody) + fn.targets = fn.targets.tail + } + emitJump(fn, done) + fn.currentBlock = done +} + +// typeSwitchStmt emits to fn code for the type switch statement s, optionally +// labelled by label. +// +func (b *builder) typeSwitchStmt(fn *Function, s *ast.TypeSwitchStmt, label *lblock) { + // We treat TypeSwitchStmt like a sequential if-else chain. + // Multiway dispatch can be recovered later by ssautil.Switches(). + + // Typeswitch lowering: + // + // var x X + // switch y := x.(type) { + // case T1, T2: S1 // >1 (y := x) + // case nil: SN // nil (y := x) + // default: SD // 0 types (y := x) + // case T3: S3 // 1 type (y := x.(T3)) + // } + // + // ...s.Init... + // x := eval x + // .caseT1: + // t1, ok1 := typeswitch,ok x <T1> + // if ok1 then goto S1 else goto .caseT2 + // .caseT2: + // t2, ok2 := typeswitch,ok x <T2> + // if ok2 then goto S1 else goto .caseNil + // .S1: + // y := x + // ...S1... + // goto done + // .caseNil: + // if t2, ok2 := typeswitch,ok x <T2> + // if x == nil then goto SN else goto .caseT3 + // .SN: + // y := x + // ...SN... + // goto done + // .caseT3: + // t3, ok3 := typeswitch,ok x <T3> + // if ok3 then goto S3 else goto default + // .S3: + // y := t3 + // ...S3... + // goto done + // .default: + // y := x + // ...SD... + // goto done + // .done: + + if s.Init != nil { + b.stmt(fn, s.Init) + } + + var x Value + switch ass := s.Assign.(type) { + case *ast.ExprStmt: // x.(type) + x = b.expr(fn, unparen(ass.X).(*ast.TypeAssertExpr).X) + case *ast.AssignStmt: // y := x.(type) + x = b.expr(fn, unparen(ass.Rhs[0]).(*ast.TypeAssertExpr).X) + } + + done := fn.newBasicBlock("typeswitch.done") + if label != nil { + label._break = done + } + var default_ *ast.CaseClause + for _, clause := range s.Body.List { + cc := clause.(*ast.CaseClause) + if cc.List == nil { + default_ = cc + continue + } + body := fn.newBasicBlock("typeswitch.body") + var next *BasicBlock + var casetype types.Type + var ti Value // ti, ok := typeassert,ok x <Ti> + for _, cond := range cc.List { + next = fn.newBasicBlock("typeswitch.next") + casetype = fn.Pkg.typeOf(cond) + var condv Value + if casetype == tUntypedNil { + condv = emitCompare(fn, token.EQL, x, nilConst(x.Type()), token.NoPos) + ti = x + } else { + yok := emitTypeTest(fn, x, casetype, cc.Case) + ti = emitExtract(fn, yok, 0) + condv = emitExtract(fn, yok, 1) + } + emitIf(fn, condv, body, next) + fn.currentBlock = next + } + if len(cc.List) != 1 { + ti = x + } + fn.currentBlock = body + b.typeCaseBody(fn, cc, ti, done) + fn.currentBlock = next + } + if default_ != nil { + b.typeCaseBody(fn, default_, x, done) + } else { + emitJump(fn, done) + } + fn.currentBlock = done +} + +func (b *builder) typeCaseBody(fn *Function, cc *ast.CaseClause, x Value, done *BasicBlock) { + if obj := fn.Pkg.info.Implicits[cc]; obj != nil { + // In a switch y := x.(type), each case clause + // implicitly declares a distinct object y. + // In a single-type case, y has that type. + // In multi-type cases, 'case nil' and default, + // y has the same type as the interface operand. + emitStore(fn, fn.addNamedLocal(obj), x, obj.Pos()) + } + fn.targets = &targets{ + tail: fn.targets, + _break: done, + } + b.stmtList(fn, cc.Body) + fn.targets = fn.targets.tail + emitJump(fn, done) +} + +// selectStmt emits to fn code for the select statement s, optionally +// labelled by label. +// +func (b *builder) selectStmt(fn *Function, s *ast.SelectStmt, label *lblock) { + // A blocking select of a single case degenerates to a + // simple send or receive. + // TODO(adonovan): opt: is this optimization worth its weight? + if len(s.Body.List) == 1 { + clause := s.Body.List[0].(*ast.CommClause) + if clause.Comm != nil { + b.stmt(fn, clause.Comm) + done := fn.newBasicBlock("select.done") + if label != nil { + label._break = done + } + fn.targets = &targets{ + tail: fn.targets, + _break: done, + } + b.stmtList(fn, clause.Body) + fn.targets = fn.targets.tail + emitJump(fn, done) + fn.currentBlock = done + return + } + } + + // First evaluate all channels in all cases, and find + // the directions of each state. + var states []*SelectState + blocking := true + debugInfo := fn.debugInfo() + for _, clause := range s.Body.List { + var st *SelectState + switch comm := clause.(*ast.CommClause).Comm.(type) { + case nil: // default case + blocking = false + continue + + case *ast.SendStmt: // ch<- i + ch := b.expr(fn, comm.Chan) + st = &SelectState{ + Dir: types.SendOnly, + Chan: ch, + Send: emitConv(fn, b.expr(fn, comm.Value), + ch.Type().Underlying().(*types.Chan).Elem()), + Pos: comm.Arrow, + } + if debugInfo { + st.DebugNode = comm + } + + case *ast.AssignStmt: // x := <-ch + recv := unparen(comm.Rhs[0]).(*ast.UnaryExpr) + st = &SelectState{ + Dir: types.RecvOnly, + Chan: b.expr(fn, recv.X), + Pos: recv.OpPos, + } + if debugInfo { + st.DebugNode = recv + } + + case *ast.ExprStmt: // <-ch + recv := unparen(comm.X).(*ast.UnaryExpr) + st = &SelectState{ + Dir: types.RecvOnly, + Chan: b.expr(fn, recv.X), + Pos: recv.OpPos, + } + if debugInfo { + st.DebugNode = recv + } + } + states = append(states, st) + } + + // We dispatch on the (fair) result of Select using a + // sequential if-else chain, in effect: + // + // idx, recvOk, r0...r_n-1 := select(...) + // if idx == 0 { // receive on channel 0 (first receive => r0) + // x, ok := r0, recvOk + // ...state0... + // } else if v == 1 { // send on channel 1 + // ...state1... + // } else { + // ...default... + // } + sel := &Select{ + States: states, + Blocking: blocking, + } + sel.setPos(s.Select) + var vars []*types.Var + vars = append(vars, varIndex, varOk) + for _, st := range states { + if st.Dir == types.RecvOnly { + tElem := st.Chan.Type().Underlying().(*types.Chan).Elem() + vars = append(vars, anonVar(tElem)) + } + } + sel.setType(types.NewTuple(vars...)) + + fn.emit(sel) + idx := emitExtract(fn, sel, 0) + + done := fn.newBasicBlock("select.done") + if label != nil { + label._break = done + } + + var defaultBody *[]ast.Stmt + state := 0 + r := 2 // index in 'sel' tuple of value; increments if st.Dir==RECV + for _, cc := range s.Body.List { + clause := cc.(*ast.CommClause) + if clause.Comm == nil { + defaultBody = &clause.Body + continue + } + body := fn.newBasicBlock("select.body") + next := fn.newBasicBlock("select.next") + emitIf(fn, emitCompare(fn, token.EQL, idx, intConst(int64(state)), token.NoPos), body, next) + fn.currentBlock = body + fn.targets = &targets{ + tail: fn.targets, + _break: done, + } + switch comm := clause.Comm.(type) { + case *ast.ExprStmt: // <-ch + if debugInfo { + v := emitExtract(fn, sel, r) + emitDebugRef(fn, states[state].DebugNode.(ast.Expr), v, false) + } + r++ + + case *ast.AssignStmt: // x := <-states[state].Chan + if comm.Tok == token.DEFINE { + fn.addLocalForIdent(comm.Lhs[0].(*ast.Ident)) + } + x := b.addr(fn, comm.Lhs[0], false) // non-escaping + v := emitExtract(fn, sel, r) + if debugInfo { + emitDebugRef(fn, states[state].DebugNode.(ast.Expr), v, false) + } + x.store(fn, v) + + if len(comm.Lhs) == 2 { // x, ok := ... + if comm.Tok == token.DEFINE { + fn.addLocalForIdent(comm.Lhs[1].(*ast.Ident)) + } + ok := b.addr(fn, comm.Lhs[1], false) // non-escaping + ok.store(fn, emitExtract(fn, sel, 1)) + } + r++ + } + b.stmtList(fn, clause.Body) + fn.targets = fn.targets.tail + emitJump(fn, done) + fn.currentBlock = next + state++ + } + if defaultBody != nil { + fn.targets = &targets{ + tail: fn.targets, + _break: done, + } + b.stmtList(fn, *defaultBody) + fn.targets = fn.targets.tail + } else { + // A blocking select must match some case. + // (This should really be a runtime.errorString, not a string.) + fn.emit(&Panic{ + X: emitConv(fn, stringConst("blocking select matched no case"), tEface), + }) + fn.currentBlock = fn.newBasicBlock("unreachable") + } + emitJump(fn, done) + fn.currentBlock = done +} + +// forStmt emits to fn code for the for statement s, optionally +// labelled by label. +// +func (b *builder) forStmt(fn *Function, s *ast.ForStmt, label *lblock) { + // ...init... + // jump loop + // loop: + // if cond goto body else done + // body: + // ...body... + // jump post + // post: (target of continue) + // ...post... + // jump loop + // done: (target of break) + if s.Init != nil { + b.stmt(fn, s.Init) + } + body := fn.newBasicBlock("for.body") + done := fn.newBasicBlock("for.done") // target of 'break' + loop := body // target of back-edge + if s.Cond != nil { + loop = fn.newBasicBlock("for.loop") + } + cont := loop // target of 'continue' + if s.Post != nil { + cont = fn.newBasicBlock("for.post") + } + if label != nil { + label._break = done + label._continue = cont + } + emitJump(fn, loop) + fn.currentBlock = loop + if loop != body { + b.cond(fn, s.Cond, body, done) + fn.currentBlock = body + } + fn.targets = &targets{ + tail: fn.targets, + _break: done, + _continue: cont, + } + b.stmt(fn, s.Body) + fn.targets = fn.targets.tail + emitJump(fn, cont) + + if s.Post != nil { + fn.currentBlock = cont + b.stmt(fn, s.Post) + emitJump(fn, loop) // back-edge + } + fn.currentBlock = done +} + +// rangeIndexed emits to fn the header for an integer-indexed loop +// over array, *array or slice value x. +// The v result is defined only if tv is non-nil. +// forPos is the position of the "for" token. +// +func (b *builder) rangeIndexed(fn *Function, x Value, tv types.Type, pos token.Pos) (k, v Value, loop, done *BasicBlock) { + // + // length = len(x) + // index = -1 + // loop: (target of continue) + // index++ + // if index < length goto body else done + // body: + // k = index + // v = x[index] + // ...body... + // jump loop + // done: (target of break) + + // Determine number of iterations. + var length Value + if arr, ok := deref(x.Type()).Underlying().(*types.Array); ok { + // For array or *array, the number of iterations is + // known statically thanks to the type. We avoid a + // data dependence upon x, permitting later dead-code + // elimination if x is pure, static unrolling, etc. + // Ranging over a nil *array may have >0 iterations. + // We still generate code for x, in case it has effects. + length = intConst(arr.Len()) + } else { + // length = len(x). + var c Call + c.Call.Value = makeLen(x.Type()) + c.Call.Args = []Value{x} + c.setType(tInt) + length = fn.emit(&c) + } + + index := fn.addLocal(tInt, token.NoPos) + emitStore(fn, index, intConst(-1), pos) + + loop = fn.newBasicBlock("rangeindex.loop") + emitJump(fn, loop) + fn.currentBlock = loop + + incr := &BinOp{ + Op: token.ADD, + X: emitLoad(fn, index), + Y: vOne, + } + incr.setType(tInt) + emitStore(fn, index, fn.emit(incr), pos) + + body := fn.newBasicBlock("rangeindex.body") + done = fn.newBasicBlock("rangeindex.done") + emitIf(fn, emitCompare(fn, token.LSS, incr, length, token.NoPos), body, done) + fn.currentBlock = body + + k = emitLoad(fn, index) + if tv != nil { + switch t := x.Type().Underlying().(type) { + case *types.Array: + instr := &Index{ + X: x, + Index: k, + } + instr.setType(t.Elem()) + v = fn.emit(instr) + + case *types.Pointer: // *array + instr := &IndexAddr{ + X: x, + Index: k, + } + instr.setType(types.NewPointer(t.Elem().Underlying().(*types.Array).Elem())) + v = emitLoad(fn, fn.emit(instr)) + + case *types.Slice: + instr := &IndexAddr{ + X: x, + Index: k, + } + instr.setType(types.NewPointer(t.Elem())) + v = emitLoad(fn, fn.emit(instr)) + + default: + panic("rangeIndexed x:" + t.String()) + } + } + return +} + +// rangeIter emits to fn the header for a loop using +// Range/Next/Extract to iterate over map or string value x. +// tk and tv are the types of the key/value results k and v, or nil +// if the respective component is not wanted. +// +func (b *builder) rangeIter(fn *Function, x Value, tk, tv types.Type, pos token.Pos) (k, v Value, loop, done *BasicBlock) { + // + // it = range x + // loop: (target of continue) + // okv = next it (ok, key, value) + // ok = extract okv #0 + // if ok goto body else done + // body: + // k = extract okv #1 + // v = extract okv #2 + // ...body... + // jump loop + // done: (target of break) + // + + if tk == nil { + tk = tInvalid + } + if tv == nil { + tv = tInvalid + } + + rng := &Range{X: x} + rng.setPos(pos) + rng.setType(tRangeIter) + it := fn.emit(rng) + + loop = fn.newBasicBlock("rangeiter.loop") + emitJump(fn, loop) + fn.currentBlock = loop + + _, isString := x.Type().Underlying().(*types.Basic) + + okv := &Next{ + Iter: it, + IsString: isString, + } + okv.setType(types.NewTuple( + varOk, + newVar("k", tk), + newVar("v", tv), + )) + fn.emit(okv) + + body := fn.newBasicBlock("rangeiter.body") + done = fn.newBasicBlock("rangeiter.done") + emitIf(fn, emitExtract(fn, okv, 0), body, done) + fn.currentBlock = body + + if tk != tInvalid { + k = emitExtract(fn, okv, 1) + } + if tv != tInvalid { + v = emitExtract(fn, okv, 2) + } + return +} + +// rangeChan emits to fn the header for a loop that receives from +// channel x until it fails. +// tk is the channel's element type, or nil if the k result is +// not wanted +// pos is the position of the '=' or ':=' token. +// +func (b *builder) rangeChan(fn *Function, x Value, tk types.Type, pos token.Pos) (k Value, loop, done *BasicBlock) { + // + // loop: (target of continue) + // ko = <-x (key, ok) + // ok = extract ko #1 + // if ok goto body else done + // body: + // k = extract ko #0 + // ... + // goto loop + // done: (target of break) + + loop = fn.newBasicBlock("rangechan.loop") + emitJump(fn, loop) + fn.currentBlock = loop + recv := &UnOp{ + Op: token.ARROW, + X: x, + CommaOk: true, + } + recv.setPos(pos) + recv.setType(types.NewTuple( + newVar("k", x.Type().Underlying().(*types.Chan).Elem()), + varOk, + )) + ko := fn.emit(recv) + body := fn.newBasicBlock("rangechan.body") + done = fn.newBasicBlock("rangechan.done") + emitIf(fn, emitExtract(fn, ko, 1), body, done) + fn.currentBlock = body + if tk != nil { + k = emitExtract(fn, ko, 0) + } + return +} + +// rangeStmt emits to fn code for the range statement s, optionally +// labelled by label. +// +func (b *builder) rangeStmt(fn *Function, s *ast.RangeStmt, label *lblock) { + var tk, tv types.Type + if s.Key != nil && !isBlankIdent(s.Key) { + tk = fn.Pkg.typeOf(s.Key) + } + if s.Value != nil && !isBlankIdent(s.Value) { + tv = fn.Pkg.typeOf(s.Value) + } + + // If iteration variables are defined (:=), this + // occurs once outside the loop. + // + // Unlike a short variable declaration, a RangeStmt + // using := never redeclares an existing variable; it + // always creates a new one. + if s.Tok == token.DEFINE { + if tk != nil { + fn.addLocalForIdent(s.Key.(*ast.Ident)) + } + if tv != nil { + fn.addLocalForIdent(s.Value.(*ast.Ident)) + } + } + + x := b.expr(fn, s.X) + + var k, v Value + var loop, done *BasicBlock + switch rt := x.Type().Underlying().(type) { + case *types.Slice, *types.Array, *types.Pointer: // *array + k, v, loop, done = b.rangeIndexed(fn, x, tv, s.For) + + case *types.Chan: + k, loop, done = b.rangeChan(fn, x, tk, s.For) + + case *types.Map, *types.Basic: // string + k, v, loop, done = b.rangeIter(fn, x, tk, tv, s.For) + + default: + panic("Cannot range over: " + rt.String()) + } + + // Evaluate both LHS expressions before we update either. + var kl, vl lvalue + if tk != nil { + kl = b.addr(fn, s.Key, false) // non-escaping + } + if tv != nil { + vl = b.addr(fn, s.Value, false) // non-escaping + } + if tk != nil { + kl.store(fn, k) + } + if tv != nil { + vl.store(fn, v) + } + + if label != nil { + label._break = done + label._continue = loop + } + + fn.targets = &targets{ + tail: fn.targets, + _break: done, + _continue: loop, + } + b.stmt(fn, s.Body) + fn.targets = fn.targets.tail + emitJump(fn, loop) // back-edge + fn.currentBlock = done +} + +// stmt lowers statement s to SSA form, emitting code to fn. +func (b *builder) stmt(fn *Function, _s ast.Stmt) { + // The label of the current statement. If non-nil, its _goto + // target is always set; its _break and _continue are set only + // within the body of switch/typeswitch/select/for/range. + // It is effectively an additional default-nil parameter of stmt(). + var label *lblock +start: + switch s := _s.(type) { + case *ast.EmptyStmt: + // ignore. (Usually removed by gofmt.) + + case *ast.DeclStmt: // Con, Var or Typ + d := s.Decl.(*ast.GenDecl) + if d.Tok == token.VAR { + for _, spec := range d.Specs { + if vs, ok := spec.(*ast.ValueSpec); ok { + b.localValueSpec(fn, vs) + } + } + } + + case *ast.LabeledStmt: + label = fn.labelledBlock(s.Label) + emitJump(fn, label._goto) + fn.currentBlock = label._goto + _s = s.Stmt + goto start // effectively: tailcall stmt(fn, s.Stmt, label) + + case *ast.ExprStmt: + b.expr(fn, s.X) + + case *ast.SendStmt: + fn.emit(&Send{ + Chan: b.expr(fn, s.Chan), + X: emitConv(fn, b.expr(fn, s.Value), + fn.Pkg.typeOf(s.Chan).Underlying().(*types.Chan).Elem()), + pos: s.Arrow, + }) + + case *ast.IncDecStmt: + op := token.ADD + if s.Tok == token.DEC { + op = token.SUB + } + loc := b.addr(fn, s.X, false) + b.assignOp(fn, loc, NewConst(exact.MakeInt64(1), loc.typ()), op) + + case *ast.AssignStmt: + switch s.Tok { + case token.ASSIGN, token.DEFINE: + b.assignStmt(fn, s.Lhs, s.Rhs, s.Tok == token.DEFINE) + + default: // +=, etc. + op := s.Tok + token.ADD - token.ADD_ASSIGN + b.assignOp(fn, b.addr(fn, s.Lhs[0], false), b.expr(fn, s.Rhs[0]), op) + } + + case *ast.GoStmt: + // The "intrinsics" new/make/len/cap are forbidden here. + // panic is treated like an ordinary function call. + v := Go{pos: s.Go} + b.setCall(fn, s.Call, &v.Call) + fn.emit(&v) + + case *ast.DeferStmt: + // The "intrinsics" new/make/len/cap are forbidden here. + // panic is treated like an ordinary function call. + v := Defer{pos: s.Defer} + b.setCall(fn, s.Call, &v.Call) + fn.emit(&v) + + // A deferred call can cause recovery from panic, + // and control resumes at the Recover block. + createRecoverBlock(fn) + + case *ast.ReturnStmt: + var results []Value + if len(s.Results) == 1 && fn.Signature.Results().Len() > 1 { + // Return of one expression in a multi-valued function. + tuple := b.exprN(fn, s.Results[0]) + ttuple := tuple.Type().(*types.Tuple) + for i, n := 0, ttuple.Len(); i < n; i++ { + results = append(results, + emitConv(fn, emitExtract(fn, tuple, i), + fn.Signature.Results().At(i).Type())) + } + } else { + // 1:1 return, or no-arg return in non-void function. + for i, r := range s.Results { + v := emitConv(fn, b.expr(fn, r), fn.Signature.Results().At(i).Type()) + results = append(results, v) + } + } + if fn.namedResults != nil { + // Function has named result parameters (NRPs). + // Perform parallel assignment of return operands to NRPs. + for i, r := range results { + emitStore(fn, fn.namedResults[i], r, s.Return) + } + } + // Run function calls deferred in this + // function when explicitly returning from it. + fn.emit(new(RunDefers)) + if fn.namedResults != nil { + // Reload NRPs to form the result tuple. + results = results[:0] + for _, r := range fn.namedResults { + results = append(results, emitLoad(fn, r)) + } + } + fn.emit(&Return{Results: results, pos: s.Return}) + fn.currentBlock = fn.newBasicBlock("unreachable") + + case *ast.BranchStmt: + var block *BasicBlock + switch s.Tok { + case token.BREAK: + if s.Label != nil { + block = fn.labelledBlock(s.Label)._break + } else { + for t := fn.targets; t != nil && block == nil; t = t.tail { + block = t._break + } + } + + case token.CONTINUE: + if s.Label != nil { + block = fn.labelledBlock(s.Label)._continue + } else { + for t := fn.targets; t != nil && block == nil; t = t.tail { + block = t._continue + } + } + + case token.FALLTHROUGH: + for t := fn.targets; t != nil && block == nil; t = t.tail { + block = t._fallthrough + } + + case token.GOTO: + block = fn.labelledBlock(s.Label)._goto + } + emitJump(fn, block) + fn.currentBlock = fn.newBasicBlock("unreachable") + + case *ast.BlockStmt: + b.stmtList(fn, s.List) + + case *ast.IfStmt: + if s.Init != nil { + b.stmt(fn, s.Init) + } + then := fn.newBasicBlock("if.then") + done := fn.newBasicBlock("if.done") + els := done + if s.Else != nil { + els = fn.newBasicBlock("if.else") + } + b.cond(fn, s.Cond, then, els) + fn.currentBlock = then + b.stmt(fn, s.Body) + emitJump(fn, done) + + if s.Else != nil { + fn.currentBlock = els + b.stmt(fn, s.Else) + emitJump(fn, done) + } + + fn.currentBlock = done + + case *ast.SwitchStmt: + b.switchStmt(fn, s, label) + + case *ast.TypeSwitchStmt: + b.typeSwitchStmt(fn, s, label) + + case *ast.SelectStmt: + b.selectStmt(fn, s, label) + + case *ast.ForStmt: + b.forStmt(fn, s, label) + + case *ast.RangeStmt: + b.rangeStmt(fn, s, label) + + default: + panic(fmt.Sprintf("unexpected statement kind: %T", s)) + } +} + +// buildFunction builds SSA code for the body of function fn. Idempotent. +func (b *builder) buildFunction(fn *Function) { + if fn.Blocks != nil { + return // building already started + } + + var recvField *ast.FieldList + var body *ast.BlockStmt + var functype *ast.FuncType + switch n := fn.syntax.(type) { + case nil: + return // not a Go source function. (Synthetic, or from object file.) + case *ast.FuncDecl: + functype = n.Type + recvField = n.Recv + body = n.Body + case *ast.FuncLit: + functype = n.Type + body = n.Body + default: + panic(n) + } + + if body == nil { + // External function. + if fn.Params == nil { + // This condition ensures we add a non-empty + // params list once only, but we may attempt + // the degenerate empty case repeatedly. + // TODO(adonovan): opt: don't do that. + + // We set Function.Params even though there is no body + // code to reference them. This simplifies clients. + if recv := fn.Signature.Recv(); recv != nil { + fn.addParamObj(recv) + } + params := fn.Signature.Params() + for i, n := 0, params.Len(); i < n; i++ { + fn.addParamObj(params.At(i)) + } + } + return + } + if fn.Prog.mode&LogSource != 0 { + defer logStack("build function %s @ %s", fn, fn.Prog.Fset.Position(fn.pos))() + } + fn.startBody() + fn.createSyntacticParams(recvField, functype) + b.stmt(fn, body) + if cb := fn.currentBlock; cb != nil && (cb == fn.Blocks[0] || cb == fn.Recover || cb.Preds != nil) { + // Control fell off the end of the function's body block. + // + // Block optimizations eliminate the current block, if + // unreachable. It is a builder invariant that + // if this no-arg return is ill-typed for + // fn.Signature.Results, this block must be + // unreachable. The sanity checker checks this. + fn.emit(new(RunDefers)) + fn.emit(new(Return)) + } + fn.finishBody() +} + +// buildFuncDecl builds SSA code for the function or method declared +// by decl in package pkg. +// +func (b *builder) buildFuncDecl(pkg *Package, decl *ast.FuncDecl) { + id := decl.Name + if isBlankIdent(id) { + return // discard + } + fn := pkg.values[pkg.info.Defs[id]].(*Function) + if decl.Recv == nil && id.Name == "init" { + var v Call + v.Call.Value = fn + v.setType(types.NewTuple()) + pkg.init.emit(&v) + } + b.buildFunction(fn) +} + +// Build calls Package.Build for each package in prog. +// Building occurs in parallel unless the BuildSerially mode flag was set. +// +// Build is intended for whole-program analysis; a typical compiler +// need only build a single package. +// +// Build is idempotent and thread-safe. +// +func (prog *Program) Build() { + var wg sync.WaitGroup + for _, p := range prog.packages { + if prog.mode&BuildSerially != 0 { + p.Build() + } else { + wg.Add(1) + go func(p *Package) { + p.Build() + wg.Done() + }(p) + } + } + wg.Wait() +} + +// Build builds SSA code for all functions and vars in package p. +// +// Precondition: CreatePackage must have been called for all of p's +// direct imports (and hence its direct imports must have been +// error-free). +// +// Build is idempotent and thread-safe. +// +func (p *Package) Build() { p.buildOnce.Do(p.build) } + +func (p *Package) build() { + if p.info == nil { + return // synthetic package, e.g. "testmain" + } + + // Ensure we have runtime type info for all exported members. + // TODO(adonovan): ideally belongs in memberFromObject, but + // that would require package creation in topological order. + for name, mem := range p.Members { + if ast.IsExported(name) { + p.Prog.needMethodsOf(mem.Type()) + } + } + if p.Prog.mode&LogSource != 0 { + defer logStack("build %s", p)() + } + init := p.init + init.startBody() + + var done *BasicBlock + + if p.Prog.mode&BareInits == 0 { + // Make init() skip if package is already initialized. + initguard := p.Var("init$guard") + doinit := init.newBasicBlock("init.start") + done = init.newBasicBlock("init.done") + emitIf(init, emitLoad(init, initguard), done, doinit) + init.currentBlock = doinit + emitStore(init, initguard, vTrue, token.NoPos) + + // Call the init() function of each package we import. + for _, pkg := range p.Pkg.Imports() { + prereq := p.Prog.packages[pkg] + if prereq == nil { + panic(fmt.Sprintf("Package(%q).Build(): unsatisfied import: Program.CreatePackage(%q) was not called", p.Pkg.Path(), pkg.Path())) + } + var v Call + v.Call.Value = prereq.init + v.Call.pos = init.pos + v.setType(types.NewTuple()) + init.emit(&v) + } + } + + var b builder + + // Initialize package-level vars in correct order. + for _, varinit := range p.info.InitOrder { + if init.Prog.mode&LogSource != 0 { + fmt.Fprintf(os.Stderr, "build global initializer %v @ %s\n", + varinit.Lhs, p.Prog.Fset.Position(varinit.Rhs.Pos())) + } + if len(varinit.Lhs) == 1 { + // 1:1 initialization: var x, y = a(), b() + var lval lvalue + if v := varinit.Lhs[0]; v.Name() != "_" { + lval = &address{addr: p.values[v].(*Global), pos: v.Pos()} + } else { + lval = blank{} + } + b.assign(init, lval, varinit.Rhs, true, nil) + } else { + // n:1 initialization: var x, y := f() + tuple := b.exprN(init, varinit.Rhs) + for i, v := range varinit.Lhs { + if v.Name() == "_" { + continue + } + emitStore(init, p.values[v].(*Global), emitExtract(init, tuple, i), v.Pos()) + } + } + } + + // Build all package-level functions, init functions + // and methods, including unreachable/blank ones. + // We build them in source order, but it's not significant. + for _, file := range p.files { + for _, decl := range file.Decls { + if decl, ok := decl.(*ast.FuncDecl); ok { + b.buildFuncDecl(p, decl) + } + } + } + + // Finish up init(). + if p.Prog.mode&BareInits == 0 { + emitJump(init, done) + init.currentBlock = done + } + init.emit(new(Return)) + init.finishBody() + + p.info = nil // We no longer need ASTs or go/types deductions. + + if p.Prog.mode&SanityCheckFunctions != 0 { + sanityCheckPackage(p) + } +} + +// Like ObjectOf, but panics instead of returning nil. +// Only valid during p's create and build phases. +func (p *Package) objectOf(id *ast.Ident) types.Object { + if o := p.info.ObjectOf(id); o != nil { + return o + } + panic(fmt.Sprintf("no types.Object for ast.Ident %s @ %s", + id.Name, p.Prog.Fset.Position(id.Pos()))) +} + +// Like TypeOf, but panics instead of returning nil. +// Only valid during p's create and build phases. +func (p *Package) typeOf(e ast.Expr) types.Type { + if T := p.info.TypeOf(e); T != nil { + return T + } + panic(fmt.Sprintf("no type for %T @ %s", + e, p.Prog.Fset.Position(e.Pos()))) +} |