compiler: fix unsafe.Sizeof and friends for AVR

This fixes runtime.printptr().

compiler.go

@@ -139,15 +139,12 @@ func NewCompiler(pkgName, triple string, dumpSSA bool) (*Compiler, error) {
 func (c *Compiler) Parse(mainPath string, buildTags []string) error {
 	tripleSplit := strings.Split(c.triple, "-")
 
-	wordSize := c.targetData.PointerSize()
-	if wordSize < 4 {
-		wordSize = 4
-	}
 	config := loader.Config{
 		TypeChecker: types.Config{
-			Sizes: &types.StdSizes{
-				int64(wordSize),
-				int64(c.targetData.PrefTypeAlignment(c.i8ptrType)),
+			Sizes: &StdSizes{
+				IntSize:  int64(c.targetData.TypeAllocSize(c.intType)),
+				PtrSize:  int64(c.targetData.PointerSize()),
+				MaxAlign: int64(c.targetData.PrefTypeAlignment(c.i8ptrType)),
 			},
 		},
 		Build: &build.Context{

sizes.go

@@ -0,0 +1,146 @@
+package main
+
+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
+		}
+	}
+	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
+		}
+		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())
+		for i := range fields {
+			fields[i] = t.Field(i)
+		}
+		offsets := s.Offsetsof(fields)
+		return offsets[n-1] + s.Sizeof(fields[n-1].Type())
+	case *types.Interface:
+		return s.PtrSize * 2
+	case *types.Pointer:
+		return s.PtrSize
+	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
+}