470 lines
12 KiB
Go
470 lines
12 KiB
Go
// 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"
|
|
)
|
|
|
|
// emitNew emits to f a new (heap Alloc) instruction allocating an
|
|
// object of type typ. pos is the optional source location.
|
|
//
|
|
func emitNew(f *Function, typ types.Type, pos token.Pos) *Alloc {
|
|
v := &Alloc{Heap: true}
|
|
v.setType(types.NewPointer(typ))
|
|
v.setPos(pos)
|
|
f.emit(v)
|
|
return v
|
|
}
|
|
|
|
// 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(deref(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.Pkg.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.
|
|
// TODO(adonovan): whence signed values?
|
|
if b, ok := y.Type().Underlying().(*types.Basic); ok && b.Info()&types.IsUnsigned == 0 {
|
|
y = emitConv(f, y, types.Typ[types.Uint64])
|
|
}
|
|
|
|
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 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 _, ok := xt.(*types.Interface); ok {
|
|
y = emitConv(f, y, x.Type())
|
|
} else if _, ok := yt.(*types.Interface); ok {
|
|
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())
|
|
//lint:ignore SA9003 no-op
|
|
} 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 type.
|
|
//
|
|
func isValuePreserving(ut_src, ut_dst types.Type) bool {
|
|
// Identical underlying types?
|
|
if structTypesIdentical(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. Conversions cannot fail dynamically.
|
|
//
|
|
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()
|
|
|
|
// Just a change of type, but not value or representation?
|
|
if isValuePreserving(ut_src, ut_dst) {
|
|
c := &ChangeType{X: val}
|
|
c.setType(typ)
|
|
return f.emit(c)
|
|
}
|
|
|
|
// Conversion to, or construction of a value of, an interface type?
|
|
if _, ok := ut_dst.(*types.Interface); ok {
|
|
// Assignment from one interface type to another?
|
|
if _, ok := ut_src.(*types.Interface); ok {
|
|
c := &ChangeInterface{X: val}
|
|
c.setType(typ)
|
|
return f.emit(c)
|
|
}
|
|
|
|
// Untyped nil constant? Return interface-typed nil constant.
|
|
if ut_src == tUntypedNil {
|
|
return nilConst(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, DefaultType(ut_src))
|
|
}
|
|
|
|
f.Pkg.Prog.needMethodsOf(val.Type())
|
|
mi := &MakeInterface{X: val}
|
|
mi.setType(typ)
|
|
return f.emit(mi)
|
|
}
|
|
|
|
// Conversion of a compile-time constant value?
|
|
if c, ok := val.(*Const); ok {
|
|
if _, ok := ut_dst.(*types.Basic); ok || c.IsNil() {
|
|
// 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)
|
|
}
|
|
|
|
// We're converting from constant to non-constant type,
|
|
// e.g. string -> []byte/[]rune.
|
|
}
|
|
|
|
// A representation-changing conversion?
|
|
// At least one of {ut_src,ut_dst} must be *Basic.
|
|
// (The other may be []byte or []rune.)
|
|
_, ok1 := ut_src.(*types.Basic)
|
|
_, ok2 := ut_dst.(*types.Basic)
|
|
if ok1 || ok2 {
|
|
c := &Convert{X: val}
|
|
c.setType(typ)
|
|
return f.emit(c)
|
|
}
|
|
|
|
panic(fmt.Sprintf("in %s: cannot convert %s (%s) to %s", f, val, val.Type(), typ))
|
|
}
|
|
|
|
// 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 {
|
|
s := &Store{
|
|
Addr: addr,
|
|
Val: emitConv(f, val, deref(addr.Type())),
|
|
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) Value {
|
|
for _, index := range indices {
|
|
fld := deref(v.Type()).Underlying().(*types.Struct).Field(index)
|
|
|
|
if isPointer(v.Type()) {
|
|
instr := &FieldAddr{
|
|
X: v,
|
|
Field: index,
|
|
}
|
|
instr.setType(types.NewPointer(fld.Type()))
|
|
v = f.emit(instr)
|
|
// Load the field's value iff indirectly embedded.
|
|
if isPointer(fld.Type()) {
|
|
v = emitLoad(f, v)
|
|
}
|
|
} else {
|
|
instr := &Field{
|
|
X: v,
|
|
Field: index,
|
|
}
|
|
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 {
|
|
fld := deref(v.Type()).Underlying().(*types.Struct).Field(index)
|
|
if isPointer(v.Type()) {
|
|
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 {
|
|
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
|
|
}
|
|
|
|
// zeroValue emits to f code to produce a zero value of type t,
|
|
// and returns it.
|
|
//
|
|
func zeroValue(f *Function, t types.Type) Value {
|
|
switch t.Underlying().(type) {
|
|
case *types.Struct, *types.Array:
|
|
return emitLoad(f, f.addLocal(t, token.NoPos))
|
|
default:
|
|
return zeroConst(t)
|
|
}
|
|
}
|
|
|
|
// 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
|
|
if f.namedResults != nil {
|
|
// Reload NRPs to form value tuple.
|
|
for _, r := range f.namedResults {
|
|
results = append(results, emitLoad(f, r))
|
|
}
|
|
} else {
|
|
R := f.Signature.Results()
|
|
for i, n := 0, R.Len(); i < n; i++ {
|
|
T := R.At(i).Type()
|
|
|
|
// Return zero value of each result type.
|
|
results = append(results, zeroValue(f, T))
|
|
}
|
|
}
|
|
f.emit(&Return{Results: results})
|
|
|
|
f.currentBlock = saved
|
|
}
|