154 lines
4.0 KiB
Go
154 lines
4.0 KiB
Go
package gotypes
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import (
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"errors"
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"go/token"
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"go/types"
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"strconv"
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"github.com/mmcloughlin/avo/operand"
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)
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var Sizes = types.SizesFor("gc", "amd64")
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type Basic struct {
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Addr operand.Mem
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Type *types.Basic
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}
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type Component interface {
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Resolve() (*Basic, error)
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Base() Component
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Len() Component
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Cap() Component
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Index(int) Component
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}
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type componenterr string
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func (c componenterr) Error() string { return string(c) }
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func (c componenterr) Resolve() (*Basic, error) { return nil, c }
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func (c componenterr) Base() Component { return c }
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func (c componenterr) Len() Component { return c }
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func (c componenterr) Cap() Component { return c }
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func (c componenterr) Index(int) Component { return c }
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type component struct {
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name string
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typ types.Type
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offset int
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}
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func NewComponent(name string, t types.Type, offset int) Component {
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return &component{
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name: name,
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typ: t,
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offset: offset,
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}
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}
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func NewComponentFromVar(v *types.Var, offset int) Component {
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return NewComponent(v.Name(), v.Type(), offset)
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}
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func (c *component) Resolve() (*Basic, error) {
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if !isprimitive(c.typ) {
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return nil, errors.New("component is not primitive")
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}
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return &Basic{
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Addr: operand.NewParamAddr(c.name, c.offset),
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Type: c.typ.(*types.Basic),
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}, nil
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}
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// Reference: https://github.com/golang/go/blob/50bd1c4d4eb4fac8ddeb5f063c099daccfb71b26/src/reflect/value.go#L1800-L1804
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//
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// type SliceHeader struct {
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// Data uintptr
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// Len int
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// Cap int
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// }
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//
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var slicehdroffsets = Sizes.Offsetsof([]*types.Var{
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types.NewField(token.NoPos, nil, "Data", types.Typ[types.Uintptr], false),
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types.NewField(token.NoPos, nil, "Len", types.Typ[types.Int], false),
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types.NewField(token.NoPos, nil, "Cap", types.Typ[types.Int], false),
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})
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func (c *component) Base() Component {
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if !isslice(c.typ) && !isstring(c.typ) {
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return componenterr("only slices and strings have base pointers")
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}
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return c.sub("_base", int(slicehdroffsets[0]), types.Typ[types.Uintptr])
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}
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func (c *component) Len() Component {
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if !isslice(c.typ) && !isstring(c.typ) {
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return componenterr("only slices and strings have length fields")
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}
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return c.sub("_len", int(slicehdroffsets[1]), types.Typ[types.Int])
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}
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func (c *component) Cap() Component {
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if !isslice(c.typ) {
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return componenterr("only slices have capacity fields")
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}
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return c.sub("_cap", int(slicehdroffsets[2]), types.Typ[types.Int])
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}
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func (c *component) Index(i int) Component {
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a, ok := c.typ.(*types.Array)
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if !ok {
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return componenterr("not array type")
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}
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if int64(i) >= a.Len() {
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return componenterr("array index out of bounds")
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}
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// Reference: https://github.com/golang/tools/blob/bcd4e47d02889ebbc25c9f4bf3d27e4124b0bf9d/go/analysis/passes/asmdecl/asmdecl.go#L482-L494
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//
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// case asmArray:
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// tu := t.Underlying().(*types.Array)
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// elem := tu.Elem()
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// // Calculate offset of each element array.
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// fields := []*types.Var{
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// types.NewVar(token.NoPos, nil, "fake0", elem),
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// types.NewVar(token.NoPos, nil, "fake1", elem),
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// }
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// offsets := arch.sizes.Offsetsof(fields)
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// elemoff := int(offsets[1])
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// for i := 0; i < int(tu.Len()); i++ {
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// cc = appendComponentsRecursive(arch, elem, cc, suffix+"_"+strconv.Itoa(i), i*elemoff)
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// }
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//
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elem := a.Elem()
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elemsize := int(Sizes.Sizeof(types.NewArray(elem, 2)) - Sizes.Sizeof(types.NewArray(elem, 1)))
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return c.sub("_"+strconv.Itoa(i), i*elemsize, elem)
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}
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func (c *component) sub(suffix string, offset int, t types.Type) *component {
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s := *c
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s.name += suffix
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s.offset += offset
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s.typ = t
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return &s
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}
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// TODO(mbm): gotypes.Component handling for structs
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// TODO(mbm): gotypes.Component handling for complex64/128
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func isslice(t types.Type) bool {
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_, ok := t.(*types.Slice)
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return ok
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}
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func isstring(t types.Type) bool {
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b, ok := t.(*types.Basic)
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return ok && b.Kind() == types.String
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}
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// isprimitive returns true if the type cannot be broken into components.
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func isprimitive(t types.Type) bool {
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b, ok := t.(*types.Basic)
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return ok && (b.Info()&(types.IsString|types.IsComplex)) == 0
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}
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