parameter loading

gotypes/components.go

@@ -0,0 +1,155 @@
+package gotypes
+
+import (
+	"errors"
+	"go/token"
+	"go/types"
+	"strconv"
+
+	"github.com/mmcloughlin/avo/operand"
+)
+
+var Sizes = types.SizesFor("gc", "amd64")
+
+type Basic struct {
+	Addr operand.Mem
+	Type *types.Basic
+}
+
+type Component interface {
+	Resolve() (*Basic, error)
+	Base() Component
+	Len() Component
+	Cap() Component
+	Index(int) Component
+}
+
+type componenterr string
+
+func (c componenterr) Error() string            { return string(c) }
+func (c componenterr) Resolve() (*Basic, error) { return nil, c }
+func (c componenterr) Base() Component          { return c }
+func (c componenterr) Len() Component           { return c }
+func (c componenterr) Cap() Component           { return c }
+func (c componenterr) Index(int) Component      { return c }
+
+type component struct {
+	name   string
+	typ    types.Type
+	offset int
+	err    error
+}
+
+func NewComponent(name string, t types.Type, offset int) Component {
+	return &component{
+		name:   name,
+		typ:    t,
+		offset: offset,
+	}
+}
+
+func NewComponentFromVar(v *types.Var, offset int) Component {
+	return NewComponent(v.Name(), v.Type(), offset)
+}
+
+func (c *component) Resolve() (*Basic, error) {
+	if !isprimitive(c.typ) {
+		return nil, errors.New("component is not primitive")
+	}
+	return &Basic{
+		Addr: operand.NewParamAddr(c.name, c.offset),
+		Type: c.typ.(*types.Basic),
+	}, nil
+}
+
+// Reference: https://github.com/golang/go/blob/50bd1c4d4eb4fac8ddeb5f063c099daccfb71b26/src/reflect/value.go#L1800-L1804
+//
+//	type SliceHeader struct {
+//		Data uintptr
+//		Len  int
+//		Cap  int
+//	}
+//
+var slicehdroffsets = Sizes.Offsetsof([]*types.Var{
+	types.NewField(token.NoPos, nil, "Data", types.Typ[types.Uintptr], false),
+	types.NewField(token.NoPos, nil, "Len", types.Typ[types.Int], false),
+	types.NewField(token.NoPos, nil, "Cap", types.Typ[types.Int], false),
+})
+
+func (c *component) Base() Component {
+	if !isslice(c.typ) && !isstring(c.typ) {
+		return componenterr("only slices and strings have base pointers")
+	}
+	return c.sub("_base", int(slicehdroffsets[0]), types.Typ[types.Uintptr])
+}
+
+func (c *component) Len() Component {
+	if !isslice(c.typ) && !isstring(c.typ) {
+		return componenterr("only slices and strings have length fields")
+	}
+	return c.sub("_len", int(slicehdroffsets[1]), types.Typ[types.Int])
+}
+
+func (c *component) Cap() Component {
+	if !isslice(c.typ) {
+		return componenterr("only slices have capacity fields")
+	}
+	return c.sub("_cap", int(slicehdroffsets[2]), types.Typ[types.Int])
+}
+
+func (c *component) Index(i int) Component {
+	a, ok := c.typ.(*types.Array)
+	if !ok {
+		return componenterr("not array type")
+	}
+	if int64(i) >= a.Len() {
+		return componenterr("array index out of bounds")
+	}
+	// Reference: https://github.com/golang/tools/blob/bcd4e47d02889ebbc25c9f4bf3d27e4124b0bf9d/go/analysis/passes/asmdecl/asmdecl.go#L482-L494
+	//
+	//		case asmArray:
+	//			tu := t.Underlying().(*types.Array)
+	//			elem := tu.Elem()
+	//			// Calculate offset of each element array.
+	//			fields := []*types.Var{
+	//				types.NewVar(token.NoPos, nil, "fake0", elem),
+	//				types.NewVar(token.NoPos, nil, "fake1", elem),
+	//			}
+	//			offsets := arch.sizes.Offsetsof(fields)
+	//			elemoff := int(offsets[1])
+	//			for i := 0; i < int(tu.Len()); i++ {
+	//				cc = appendComponentsRecursive(arch, elem, cc, suffix+"_"+strconv.Itoa(i), i*elemoff)
+	//			}
+	//
+	elem := a.Elem()
+	elemsize := int(Sizes.Sizeof(types.NewArray(elem, 2)) - Sizes.Sizeof(types.NewArray(elem, 1)))
+	return c.sub("_"+strconv.Itoa(i), i*elemsize, elem)
+}
+
+func (c *component) sub(suffix string, offset int, t types.Type) *component {
+	var s *component
+	*s = *c
+	s.name += suffix
+	s.offset += offset
+	s.typ = t
+	return s
+}
+
+// TODO(mbm): gotypes.Component handling for structs
+// TODO(mbm): gotypes.Component handling for complex64/128
+
+func isslice(t types.Type) bool {
+	_, ok := t.(*types.Slice)
+	return ok
+}
+
+func isstring(t types.Type) bool {
+	b, ok := t.(*types.Basic)
+	return ok && b.Kind() == types.String
+}
+
+// isprimitive returns true if the type cannot be broken into components.
+func isprimitive(t types.Type) bool {
+	b, ok := t.(*types.Basic)
+	return ok && (b.Info()&(types.IsString|types.IsComplex)) == 0
+}