// 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)
}
}
// 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
}
// indexExpr generates code for array accesses (a[x], etc).
func (c *compiler) indexExpr(e *ast.IndexExpr, lv *arch.LV) *node {
var lv2 arch.LV
n := c.exprInternal(e.X, lv)
lv.Type = lv.Type.Underlying()
n = c.indirection(e, n, lv)
m := c.exprInternal(e.Index, &lv2)
m = c.rvalue(m, &lv2)
record, isRecord := lv.Type.(*types.Record)
if !isRecord && lv.Type != types.Typ[types.Char] {
// if it is not a record, we just need to scale
// it by the sizeof of the type
m = newNode(opScale, nil, nil, m, nil)
} else if isRecord {
// if it is a struct, we use sizeof to figure
// out the size to multiply by to get to the index
lv2.Size = c.cg.Sizeof(record)
m = newNode(opScaleBy, &lv2, nil, m, nil)
}
lv.Ident = false
lv.Addressable = true
return newNode(opAdd, lv, &lv2, n, m)
}
// indirection dereferences a pointer and generate code to load it.
func (c *compiler) indirection(e ast.Expr, n *node, lv *arch.LV) *node {
pos := e.Span().Start
n = c.rvalue(n, lv)
ptr, ok := lv.Type.(*types.Pointer)
if !ok {
c.errorf(pos, "indirection through non pointer")
return nil
} else if isVoidPointer(lv.Type) {
c.errorf(pos, "dereferencing void pointer")
return nil
}
lv.Ident = false
lv.Type = ptr.Elem().Underlying()
return n
}
// 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
}