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Diffstat (limited to 'vendor/golang.org/x/tools/go/ssa/emit.go')
| -rw-r--r-- | vendor/golang.org/x/tools/go/ssa/emit.go | 614 |
1 files changed, 614 insertions, 0 deletions
diff --git a/vendor/golang.org/x/tools/go/ssa/emit.go b/vendor/golang.org/x/tools/go/ssa/emit.go new file mode 100644 index 0000000..c664ff8 --- /dev/null +++ b/vendor/golang.org/x/tools/go/ssa/emit.go @@ -0,0 +1,614 @@ +// 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 + +// Helpers for emitting SSA instructions. + +import ( + "fmt" + "go/ast" + "go/token" + "go/types" + + "golang.org/x/tools/internal/typeparams" +) + +// emitAlloc emits to f a new Alloc instruction allocating a variable +// of type typ. +// +// The caller must set Alloc.Heap=true (for an heap-allocated variable) +// or add the Alloc to f.Locals (for a frame-allocated variable). +// +// During building, a variable in f.Locals may have its Heap flag +// set when it is discovered that its address is taken. +// These Allocs are removed from f.Locals at the end. +// +// The builder should generally call one of the emit{New,Local,LocalVar} wrappers instead. +func emitAlloc(f *Function, typ types.Type, pos token.Pos, comment string) *Alloc { + v := &Alloc{Comment: comment} + v.setType(types.NewPointer(typ)) + v.setPos(pos) + f.emit(v) + return v +} + +// emitNew emits to f a new Alloc instruction heap-allocating a +// variable of type typ. pos is the optional source location. +func emitNew(f *Function, typ types.Type, pos token.Pos, comment string) *Alloc { + alloc := emitAlloc(f, typ, pos, comment) + alloc.Heap = true + return alloc +} + +// emitLocal creates a local var for (t, pos, comment) and +// emits an Alloc instruction for it. +// +// (Use this function or emitNew for synthetic variables; +// for source-level variables in the same function, use emitLocalVar.) +func emitLocal(f *Function, t types.Type, pos token.Pos, comment string) *Alloc { + local := emitAlloc(f, t, pos, comment) + f.Locals = append(f.Locals, local) + return local +} + +// emitLocalVar creates a local var for v and emits an Alloc instruction for it. +// Subsequent calls to f.lookup(v) return it. +// It applies the appropriate generic instantiation to the type. +func emitLocalVar(f *Function, v *types.Var) *Alloc { + alloc := emitLocal(f, f.typ(v.Type()), v.Pos(), v.Name()) + f.vars[v] = alloc + return alloc +} + +// emitLoad emits to f an instruction to load the address addr into a +// new temporary, and returns the value so defined. +func emitLoad(f *Function, addr Value) *UnOp { + v := &UnOp{Op: token.MUL, X: addr} + v.setType(typeparams.MustDeref(addr.Type())) + f.emit(v) + return v +} + +// emitDebugRef emits to f a DebugRef pseudo-instruction associating +// expression e with value v. +func emitDebugRef(f *Function, e ast.Expr, v Value, isAddr bool) { + if !f.debugInfo() { + return // debugging not enabled + } + if v == nil || e == nil { + panic("nil") + } + var obj types.Object + e = unparen(e) + if id, ok := e.(*ast.Ident); ok { + if isBlankIdent(id) { + return + } + obj = f.objectOf(id) + switch obj.(type) { + case *types.Nil, *types.Const, *types.Builtin: + return + } + } + f.emit(&DebugRef{ + X: v, + Expr: e, + IsAddr: isAddr, + object: obj, + }) +} + +// emitArith emits to f code to compute the binary operation op(x, y) +// where op is an eager shift, logical or arithmetic operation. +// (Use emitCompare() for comparisons and Builder.logicalBinop() for +// non-eager operations.) +func emitArith(f *Function, op token.Token, x, y Value, t types.Type, pos token.Pos) Value { + switch op { + case token.SHL, token.SHR: + x = emitConv(f, x, t) + // y may be signed or an 'untyped' constant. + + // There is a runtime panic if y is signed and <0. Instead of inserting a check for y<0 + // and converting to an unsigned value (like the compiler) leave y as is. + + if isUntyped(y.Type().Underlying()) { + // Untyped conversion: + // Spec https://go.dev/ref/spec#Operators: + // The right operand in a shift expression must have integer type or be an untyped constant + // representable by a value of type uint. + y = emitConv(f, y, types.Typ[types.Uint]) + } + + case token.ADD, token.SUB, token.MUL, token.QUO, token.REM, token.AND, token.OR, token.XOR, token.AND_NOT: + x = emitConv(f, x, t) + y = emitConv(f, y, t) + + default: + panic("illegal op in emitArith: " + op.String()) + + } + v := &BinOp{ + Op: op, + X: x, + Y: y, + } + v.setPos(pos) + v.setType(t) + return f.emit(v) +} + +// emitCompare emits to f code compute the boolean result of +// comparison 'x op y'. +func emitCompare(f *Function, op token.Token, x, y Value, pos token.Pos) Value { + xt := x.Type().Underlying() + yt := y.Type().Underlying() + + // Special case to optimise a tagless SwitchStmt so that + // these are equivalent + // switch { case e: ...} + // switch true { case e: ... } + // if e==true { ... } + // even in the case when e's type is an interface. + // TODO(adonovan): opt: generalise to x==true, false!=y, etc. + if x == vTrue && op == token.EQL { + if yt, ok := yt.(*types.Basic); ok && yt.Info()&types.IsBoolean != 0 { + return y + } + } + + if types.Identical(xt, yt) { + // no conversion necessary + } else if isNonTypeParamInterface(x.Type()) { + y = emitConv(f, y, x.Type()) + } else if isNonTypeParamInterface(y.Type()) { + x = emitConv(f, x, y.Type()) + } else if _, ok := x.(*Const); ok { + x = emitConv(f, x, y.Type()) + } else if _, ok := y.(*Const); ok { + y = emitConv(f, y, x.Type()) + } else { + // other cases, e.g. channels. No-op. + } + + v := &BinOp{ + Op: op, + X: x, + Y: y, + } + v.setPos(pos) + v.setType(tBool) + return f.emit(v) +} + +// isValuePreserving returns true if a conversion from ut_src to +// ut_dst is value-preserving, i.e. just a change of type. +// Precondition: neither argument is a named or alias type. +func isValuePreserving(ut_src, ut_dst types.Type) bool { + // Identical underlying types? + if types.IdenticalIgnoreTags(ut_dst, ut_src) { + return true + } + + switch ut_dst.(type) { + case *types.Chan: + // Conversion between channel types? + _, ok := ut_src.(*types.Chan) + return ok + + case *types.Pointer: + // Conversion between pointers with identical base types? + _, ok := ut_src.(*types.Pointer) + return ok + } + return false +} + +// emitConv emits to f code to convert Value val to exactly type typ, +// and returns the converted value. Implicit conversions are required +// by language assignability rules in assignments, parameter passing, +// etc. +func emitConv(f *Function, val Value, typ types.Type) Value { + t_src := val.Type() + + // Identical types? Conversion is a no-op. + if types.Identical(t_src, typ) { + return val + } + ut_dst := typ.Underlying() + ut_src := t_src.Underlying() + + // Conversion to, or construction of a value of, an interface type? + if isNonTypeParamInterface(typ) { + // Interface name change? + if isValuePreserving(ut_src, ut_dst) { + c := &ChangeType{X: val} + c.setType(typ) + return f.emit(c) + } + + // Assignment from one interface type to another? + if isNonTypeParamInterface(t_src) { + c := &ChangeInterface{X: val} + c.setType(typ) + return f.emit(c) + } + + // Untyped nil constant? Return interface-typed nil constant. + if ut_src == tUntypedNil { + return zeroConst(typ) + } + + // Convert (non-nil) "untyped" literals to their default type. + if t, ok := ut_src.(*types.Basic); ok && t.Info()&types.IsUntyped != 0 { + val = emitConv(f, val, types.Default(ut_src)) + } + + // Record the types of operands to MakeInterface, if + // non-parameterized, as they are the set of runtime types. + t := val.Type() + if f.typeparams.Len() == 0 || !f.Prog.isParameterized(t) { + addRuntimeType(f.Prog, t) + } + + mi := &MakeInterface{X: val} + mi.setType(typ) + return f.emit(mi) + } + + // In the common case, the typesets of src and dst are singletons + // and we emit an appropriate conversion. But if either contains + // a type parameter, the conversion may represent a cross product, + // in which case which we emit a MultiConvert. + dst_terms := typeSetOf(ut_dst) + src_terms := typeSetOf(ut_src) + + // conversionCase describes an instruction pattern that maybe emitted to + // model d <- s for d in dst_terms and s in src_terms. + // Multiple conversions can match the same pattern. + type conversionCase uint8 + const ( + changeType conversionCase = 1 << iota + sliceToArray + sliceToArrayPtr + sliceTo0Array + sliceTo0ArrayPtr + convert + ) + // classify the conversion case of a source type us to a destination type ud. + // us and ud are underlying types (not *Named or *Alias) + classify := func(us, ud types.Type) conversionCase { + // Just a change of type, but not value or representation? + if isValuePreserving(us, ud) { + return changeType + } + + // Conversion from slice to array or slice to array pointer? + if slice, ok := us.(*types.Slice); ok { + var arr *types.Array + var ptr bool + // Conversion from slice to array pointer? + switch d := ud.(type) { + case *types.Array: + arr = d + case *types.Pointer: + arr, _ = d.Elem().Underlying().(*types.Array) + ptr = true + } + if arr != nil && types.Identical(slice.Elem(), arr.Elem()) { + if arr.Len() == 0 { + if ptr { + return sliceTo0ArrayPtr + } else { + return sliceTo0Array + } + } + if ptr { + return sliceToArrayPtr + } else { + return sliceToArray + } + } + } + + // The only remaining case in well-typed code is a representation- + // changing conversion of basic types (possibly with []byte/[]rune). + if !isBasic(us) && !isBasic(ud) { + panic(fmt.Sprintf("in %s: cannot convert term %s (%s [within %s]) to type %s [within %s]", f, val, val.Type(), us, typ, ud)) + } + return convert + } + + var classifications conversionCase + for _, s := range src_terms { + us := s.Type().Underlying() + for _, d := range dst_terms { + ud := d.Type().Underlying() + classifications |= classify(us, ud) + } + } + if classifications == 0 { + panic(fmt.Sprintf("in %s: cannot convert %s (%s) to %s", f, val, val.Type(), typ)) + } + + // Conversion of a compile-time constant value? + if c, ok := val.(*Const); ok { + // Conversion to a basic type? + if isBasic(ut_dst) { + // Conversion of a compile-time constant to + // another constant type results in a new + // constant of the destination type and + // (initially) the same abstract value. + // We don't truncate the value yet. + return NewConst(c.Value, typ) + } + // Can we always convert from zero value without panicking? + const mayPanic = sliceToArray | sliceToArrayPtr + if c.Value == nil && classifications&mayPanic == 0 { + return NewConst(nil, typ) + } + + // We're converting from constant to non-constant type, + // e.g. string -> []byte/[]rune. + } + + switch classifications { + case changeType: // representation-preserving change + c := &ChangeType{X: val} + c.setType(typ) + return f.emit(c) + + case sliceToArrayPtr, sliceTo0ArrayPtr: // slice to array pointer + c := &SliceToArrayPointer{X: val} + c.setType(typ) + return f.emit(c) + + case sliceToArray: // slice to arrays (not zero-length) + ptype := types.NewPointer(typ) + p := &SliceToArrayPointer{X: val} + p.setType(ptype) + x := f.emit(p) + unOp := &UnOp{Op: token.MUL, X: x} + unOp.setType(typ) + return f.emit(unOp) + + case sliceTo0Array: // slice to zero-length arrays (constant) + return zeroConst(typ) + + case convert: // representation-changing conversion + c := &Convert{X: val} + c.setType(typ) + return f.emit(c) + + default: // multiple conversion + c := &MultiConvert{X: val, from: src_terms, to: dst_terms} + c.setType(typ) + return f.emit(c) + } +} + +// emitTypeCoercion emits to f code to coerce the type of a +// Value v to exactly type typ, and returns the coerced value. +// +// Requires that coercing v.Typ() to typ is a value preserving change. +// +// Currently used only when v.Type() is a type instance of typ or vice versa. +// A type v is a type instance of a type t if there exists a +// type parameter substitution σ s.t. σ(v) == t. Example: +// +// σ(func(T) T) == func(int) int for σ == [T ↦ int] +// +// This happens in instantiation wrappers for conversion +// from an instantiation to a parameterized type (and vice versa) +// with σ substituting f.typeparams by f.typeargs. +func emitTypeCoercion(f *Function, v Value, typ types.Type) Value { + if types.Identical(v.Type(), typ) { + return v // no coercion needed + } + // TODO(taking): for instances should we record which side is the instance? + c := &ChangeType{ + X: v, + } + c.setType(typ) + f.emit(c) + return c +} + +// emitStore emits to f an instruction to store value val at location +// addr, applying implicit conversions as required by assignability rules. +func emitStore(f *Function, addr, val Value, pos token.Pos) *Store { + typ := typeparams.MustDeref(addr.Type()) + s := &Store{ + Addr: addr, + Val: emitConv(f, val, typ), + pos: pos, + } + f.emit(s) + return s +} + +// emitJump emits to f a jump to target, and updates the control-flow graph. +// Postcondition: f.currentBlock is nil. +func emitJump(f *Function, target *BasicBlock) { + b := f.currentBlock + b.emit(new(Jump)) + addEdge(b, target) + f.currentBlock = nil +} + +// emitIf emits to f a conditional jump to tblock or fblock based on +// cond, and updates the control-flow graph. +// Postcondition: f.currentBlock is nil. +func emitIf(f *Function, cond Value, tblock, fblock *BasicBlock) { + b := f.currentBlock + b.emit(&If{Cond: cond}) + addEdge(b, tblock) + addEdge(b, fblock) + f.currentBlock = nil +} + +// emitExtract emits to f an instruction to extract the index'th +// component of tuple. It returns the extracted value. +func emitExtract(f *Function, tuple Value, index int) Value { + e := &Extract{Tuple: tuple, Index: index} + e.setType(tuple.Type().(*types.Tuple).At(index).Type()) + return f.emit(e) +} + +// emitTypeAssert emits to f a type assertion value := x.(t) and +// returns the value. x.Type() must be an interface. +func emitTypeAssert(f *Function, x Value, t types.Type, pos token.Pos) Value { + a := &TypeAssert{X: x, AssertedType: t} + a.setPos(pos) + a.setType(t) + return f.emit(a) +} + +// emitTypeTest emits to f a type test value,ok := x.(t) and returns +// a (value, ok) tuple. x.Type() must be an interface. +func emitTypeTest(f *Function, x Value, t types.Type, pos token.Pos) Value { + a := &TypeAssert{ + X: x, + AssertedType: t, + CommaOk: true, + } + a.setPos(pos) + a.setType(types.NewTuple( + newVar("value", t), + varOk, + )) + return f.emit(a) +} + +// emitTailCall emits to f a function call in tail position. The +// caller is responsible for all fields of 'call' except its type. +// Intended for wrapper methods. +// Precondition: f does/will not use deferred procedure calls. +// Postcondition: f.currentBlock is nil. +func emitTailCall(f *Function, call *Call) { + tresults := f.Signature.Results() + nr := tresults.Len() + if nr == 1 { + call.typ = tresults.At(0).Type() + } else { + call.typ = tresults + } + tuple := f.emit(call) + var ret Return + switch nr { + case 0: + // no-op + case 1: + ret.Results = []Value{tuple} + default: + for i := 0; i < nr; i++ { + v := emitExtract(f, tuple, i) + // TODO(adonovan): in principle, this is required: + // v = emitConv(f, o.Type, f.Signature.Results[i].Type) + // but in practice emitTailCall is only used when + // the types exactly match. + ret.Results = append(ret.Results, v) + } + } + f.emit(&ret) + f.currentBlock = nil +} + +// emitImplicitSelections emits to f code to apply the sequence of +// implicit field selections specified by indices to base value v, and +// returns the selected value. +// +// If v is the address of a struct, the result will be the address of +// a field; if it is the value of a struct, the result will be the +// value of a field. +func emitImplicitSelections(f *Function, v Value, indices []int, pos token.Pos) Value { + for _, index := range indices { + if isPointerCore(v.Type()) { + fld := fieldOf(typeparams.MustDeref(v.Type()), index) + instr := &FieldAddr{ + X: v, + Field: index, + } + instr.setPos(pos) + instr.setType(types.NewPointer(fld.Type())) + v = f.emit(instr) + // Load the field's value iff indirectly embedded. + if isPointerCore(fld.Type()) { + v = emitLoad(f, v) + } + } else { + fld := fieldOf(v.Type(), index) + instr := &Field{ + X: v, + Field: index, + } + instr.setPos(pos) + instr.setType(fld.Type()) + v = f.emit(instr) + } + } + return v +} + +// emitFieldSelection emits to f code to select the index'th field of v. +// +// If wantAddr, the input must be a pointer-to-struct and the result +// will be the field's address; otherwise the result will be the +// field's value. +// Ident id is used for position and debug info. +func emitFieldSelection(f *Function, v Value, index int, wantAddr bool, id *ast.Ident) Value { + if isPointerCore(v.Type()) { + fld := fieldOf(typeparams.MustDeref(v.Type()), index) + instr := &FieldAddr{ + X: v, + Field: index, + } + instr.setPos(id.Pos()) + instr.setType(types.NewPointer(fld.Type())) + v = f.emit(instr) + // Load the field's value iff we don't want its address. + if !wantAddr { + v = emitLoad(f, v) + } + } else { + fld := fieldOf(v.Type(), index) + instr := &Field{ + X: v, + Field: index, + } + instr.setPos(id.Pos()) + instr.setType(fld.Type()) + v = f.emit(instr) + } + emitDebugRef(f, id, v, wantAddr) + return v +} + +// createRecoverBlock emits to f a block of code to return after a +// recovered panic, and sets f.Recover to it. +// +// If f's result parameters are named, the code loads and returns +// their current values, otherwise it returns the zero values of their +// type. +// +// Idempotent. +func createRecoverBlock(f *Function) { + if f.Recover != nil { + return // already created + } + saved := f.currentBlock + + f.Recover = f.newBasicBlock("recover") + f.currentBlock = f.Recover + + var results []Value + // Reload NRPs to form value tuple. + for _, nr := range f.results { + results = append(results, emitLoad(f, nr)) + } + + f.emit(&Return{Results: results}) + + f.currentBlock = saved +} |