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|
package compiler
import (
"go/types"
)
// The code in this file has been copied from
// https://golang.org/src/go/types/sizes.go and modified to allow for int and
// pointer sizes to differ.
// The original license can be found here:
// https://golang.org/LICENSE
type stdSizes struct {
IntSize int64
PtrSize int64
MaxAlign int64
}
func (s *stdSizes) Alignof(T types.Type) int64 {
// For arrays and structs, alignment is defined in terms
// of alignment of the elements and fields, respectively.
switch t := T.Underlying().(type) {
case *types.Array:
// spec: "For a variable x of array type: unsafe.Alignof(x)
// is the same as unsafe.Alignof(x[0]), but at least 1."
return s.Alignof(t.Elem())
case *types.Struct:
// spec: "For a variable x of struct type: unsafe.Alignof(x)
// is the largest of the values unsafe.Alignof(x.f) for each
// field f of x, but at least 1."
max := int64(1)
for i := 0; i < t.NumFields(); i++ {
f := t.Field(i)
if a := s.Alignof(f.Type()); a > max {
max = a
}
}
return max
case *types.Slice, *types.Interface:
// Multiword data structures are effectively structs
// in which each element has size WordSize.
return s.PtrSize
case *types.Basic:
// Strings are like slices and interfaces.
if t.Info()&types.IsString != 0 {
return s.PtrSize
}
case *types.Signature:
// Even though functions in tinygo are 2 pointers, they are not 2 pointer aligned
return s.PtrSize
}
a := s.Sizeof(T) // may be 0
// spec: "For a variable x of any type: unsafe.Alignof(x) is at least 1."
if a < 1 {
return 1
}
// complex{64,128} are aligned like [2]float{32,64}.
if t, ok := T.Underlying().(*types.Basic); ok && t.Info()&types.IsComplex != 0 {
a /= 2
}
if a > s.MaxAlign {
return s.MaxAlign
}
return a
}
func (s *stdSizes) Offsetsof(fields []*types.Var) []int64 {
offsets := make([]int64, len(fields))
var o int64
for i, f := range fields {
a := s.Alignof(f.Type())
o = align(o, a)
offsets[i] = o
o += s.Sizeof(f.Type())
}
return offsets
}
var basicSizes = [...]byte{
types.Bool: 1,
types.Int8: 1,
types.Int16: 2,
types.Int32: 4,
types.Int64: 8,
types.Uint8: 1,
types.Uint16: 2,
types.Uint32: 4,
types.Uint64: 8,
types.Float32: 4,
types.Float64: 8,
types.Complex64: 8,
types.Complex128: 16,
}
func (s *stdSizes) Sizeof(T types.Type) int64 {
switch t := T.Underlying().(type) {
case *types.Basic:
k := t.Kind()
if int(k) < len(basicSizes) {
if s := basicSizes[k]; s > 0 {
return int64(s)
}
}
if k == types.String {
return s.PtrSize * 2
}
if k == types.Int || k == types.Uint {
return s.IntSize
}
if k == types.Uintptr {
return s.PtrSize
}
if k == types.UnsafePointer {
return s.PtrSize
}
if k == types.Invalid {
return 0 // only relevant when there is a type error somewhere
}
panic("unknown basic type: " + t.String())
case *types.Array:
n := t.Len()
if n <= 0 {
return 0
}
// n > 0
a := s.Alignof(t.Elem())
z := s.Sizeof(t.Elem())
return align(z, a)*(n-1) + z
case *types.Slice:
return s.PtrSize * 3
case *types.Struct:
n := t.NumFields()
if n == 0 {
return 0
}
fields := make([]*types.Var, t.NumFields())
maxAlign := int64(1)
for i := range fields {
field := t.Field(i)
fields[i] = field
al := s.Alignof(field.Type())
if al > maxAlign {
maxAlign = al
}
}
// Pick the size that fits this struct and add some alignment. Some
// structs have some extra padding at the end which should also be taken
// care of:
// struct { int32 n; byte b }
offsets := s.Offsetsof(fields)
return align(offsets[n-1]+s.Sizeof(fields[n-1].Type()), maxAlign)
case *types.Interface:
return s.PtrSize * 2
case *types.Pointer, *types.Chan, *types.Map:
return s.PtrSize
case *types.Signature:
// Func values in TinyGo are two words in size.
return s.PtrSize * 2
default:
panic("unknown type: " + t.String())
}
}
// align returns the smallest y >= x such that y % a == 0.
func align(x, a int64) int64 {
y := x + a - 1
return y - y%a
}
|
