// ident generates code for an identifier by loading it into the accumulator.
func (c *compiler) ident(e *ast.Ident, lv *arch.LV, tv types.TypeAndValue) *node {
lv.Ident = true
lv.Type = tv.Type.Underlying()
lv.Name = e.Name
_, isFunc := tv.Type.(*types.Signature)
if isFunc {
if x, ok := c.Uses[e]; ok {
switch x := x.(type) {
case *types.Func:
lv.Storage = x.Storage()
return newNode(opAddr, lv, nil, nil, nil)
case *types.Fwrd:
return newNode(opAddr, lv, nil, nil, nil)
}
}
}
v, found := c.variable(e, c.Uses)
if !found {
lv.Ident = false
return nil
}
s, found := c.symbol(v)
if !found {
lv.Ident = false
return nil
}
_, isRecord := lv.Type.(*types.Record)
// arrays decay to pointers, so we need to get the original type
// because the type and value by the typechecker is recorded as a pointer
array, isArray := v.Type().(*types.Array)
lv.Addr = s.Addr
lv.Value = s.Value
lv.Storage = v.Storage()
switch {
// constants
case tv.Value != nil:
lv.Value = tv.Value
return newNode(opLit, lv, nil, nil, nil)
case isArray:
lv.Type = types.NewPointer(array.Elem(), nil)
return newNode(opAddr, lv, nil, nil, nil)
case isRecord:
lv.Ident = false
return newNode(opAddr, lv, nil, nil, nil)
// variable that a integer or a pointer
default:
lv.Addressable = true
return newNode(opIdent, lv, nil, nil, nil)
}
}
// reduce transforms expressions into equivalent but faster expressions.
func (c *compiler) reduce(n *node) *node {
var vl, vr int
var lv arch.LV
op := n.op
cl := n.left.op == opLit
cr := n.right.op == opLit
if cl {
vl, _ = strconv.Atoi(n.left.lv[0].Value.String())
}
if cr {
vr, _ = strconv.Atoi(n.right.lv[0].Value.String())
}
switch {
case (op == opPlus || op == opAdd) && cr && vr == 0: // x+0 -> x
return n.left
case (op == opPlus || op == opAdd) && cl && vl == 0: // 0+x -> x
return n.right
case op == opSub && cr && vr == 0: // x-0 -> x
return n.left
case op == opSub && cl && vl == 0: // 0-x -> -x
return newNode(opNeg, nil, nil, n.right, nil)
case op == opMul && ((cl && vl == 0) || (cr && vr == 0)): // 0*x -> 0 || x*0 -> 0
lv.Value = constant.MakeInt64(0)
return newNode(opLit, &lv, nil, nil, nil)
case op == opMul || op == opDiv: // reduce x*(2^n) or x/(2^n) to x<<n or x>>n
lim := c.cg.Int()*8 - 1
for i, k := 0, 1; i < lim; i, k = i+1, k<<1 {
lv.Value = constant.MakeInt64(int64(i))
m := newNode(opLit, &lv, nil, nil, nil)
if cr && k == vr {
if op == opMul {
return newNode(opLsh, nil, nil, n.left, m)
} else {
return newNode(opRsh, nil, nil, n.left, m)
}
} else if cl && k == vl && op == opMul {
return newNode(opLsh, nil, nil, n.right, m)
}
}
}
return n
}
// sizeofExpr generates code for a sizeof(x) expression.
func (c *compiler) sizeofExpr(e *ast.SizeofExpr, lv *arch.LV, tv types.TypeAndValue) *node {
lv.Value = tv.Value
lv.Addressable = false
n := newNode(opLit, lv, nil, nil, nil)
return n
}
// selectorExpr generates code for record accesses (a.x, a->x, etc)
func (c *compiler) selectorExpr(e *ast.SelectorExpr, lv *arch.LV) *node {
sel, found := c.Selections[e]
if !found {
c.errorf(e.Op.Pos, "no selection expression information found")
return nil
}
n := c.exprInternal(e.X, lv)
if sel.Indirect() {
n = c.rvalue(n, lv)
lv.Ident = false
}
lv.Addressable = true
if !sel.IsUnion() && sel.Offset() != 0 {
lv.Value = constant.MakeInt64(sel.Offset())
m := newNode(opLit, lv, nil, nil, nil)
n = newNode(opAdd, lv, nil, n, m)
}
if isArray(sel.Obj().Type()) {
lv.Addressable = false
}
lv.Type = sel.Type().Underlying()
return n
}
// fold1 folds constant unary expressions.
func (c *compiler) fold1(n *node) *node {
var lv arch.LV
switch n.op {
case opScale:
v, _ := strconv.Atoi(n.left.lv[0].Value.String())
lv.Value = constant.MakeInt64(int64(v * c.cg.Int()))
default:
return n
}
return newNode(opLit, &lv, nil, nil, nil)
}
// exprInternal is the main function for generating code by figuring
// out what kind of expression it is.
func (c *compiler) exprInternal(e ast.Expr, lv *arch.LV) *node {
lv.Ident = false
pos := e.Span().Start
tv, found := c.typAndValue(e)
if !found {
return nil
}
// for constants we can just get the value right away
if tv.Value != nil {
lv.Type = tv.Type
lv.Value = tv.Value
switch tv.Type {
case types.Typ[types.UntypedString]:
str, err := strconv.Unquote(tv.Value.String())
if err != nil {
c.errorf(pos, "invalid constant %v: %v", tv.Value, err)
}
c.cg.Data()
lab := c.cg.Label()
c.cg.Lab(lab)
c.cg.Defs(str)
c.cg.Defb(0)
c.cg.Align(len(str)+1, c.cg.Int())
lv.Addr = lab
return newNode(opLdlab, lv, nil, nil, nil)
default:
return newNode(opLit, lv, nil, nil, nil)
}
}
switch e := e.(type) {
case *ast.BinaryExpr:
return c.binaryExpr(e, lv)
case *ast.UnaryExpr:
return c.unaryExpr(e, lv)
case *ast.SizeofExpr:
return c.sizeofExpr(e, lv, tv)
case *ast.StarExpr:
return c.starExpr(e, lv)
case *ast.CallExpr:
return c.callExpr(e, lv)
case *ast.Ident:
return c.ident(e, lv, tv)
case *ast.ParenExpr:
return c.exprInternal(e.X, lv)
case *ast.IndexExpr:
return c.indexExpr(e, lv)
case *ast.SelectorExpr:
return c.selectorExpr(e, lv)
case *ast.CondExpr:
return c.condExpr(e, lv)
case *ast.CastExpr:
return c.castExpr(e, lv, tv)
case *ast.BasicType:
lv.Type = tv.Type
default:
c.errorf(pos, "invalid expression: %T", e)
}
return nil
}
