Add field and index addr elaboration

ir2/instr.go

@@ -38,14 +38,16 @@ func (in *Instr) Update(op Op, typ types.Type, args ...interface{}) {
 func (in *Instr) update(fn *Func, op Op, typ types.Type, args []interface{}) {
 	in.Op = op
 
-	if tuple, ok := typ.(*types.Tuple); ok {
-		for i := 0; i < tuple.Len(); i++ {
-			v := tuple.At(i)
-
-			in.updateDef(fn, i, v.Type())
+	if !op.IsSink() {
+		if tuple, ok := typ.(*types.Tuple); ok {
+			for i := 0; i < tuple.Len(); i++ {
+				v := tuple.At(i)
+
+				in.updateDef(fn, i, v.Type())
+			}
+		} else if typ != nil {
+			in.updateDef(fn, 0, typ)
 		}
-	} else if typ != nil {
-		in.updateDef(fn, 0, typ)
 	}
 
 	for i, a := range args {
@@ -100,7 +102,8 @@ func (in *Instr) AddDef(val *Value) *Value {
 // updateDef updates an existing def or adds one if necessary
 func (in *Instr) updateDef(fn *Func, i int, typ types.Type) *Value {
 	typ = validType(typ)
-	if len(in.defs) < i {
+
+	if i < len(in.defs) {
 		in.defs[i].Type = typ
 		return in.defs[i]
 	}

ir2/structs.go

@@ -138,6 +138,7 @@ type Op interface {
 	IsCompare() bool
 	IsCopy() bool
 	IsCommutative() bool
+	IsSink() bool
 }
 
 // Instr is an instruction that may define one or more Values,

xform2/elaboration/fieldaddrs.go

@@ -0,0 +1,42 @@
+package elaboration
+
+import (
+	"go/types"
+
+	"github.com/rj45/nanogo/ir/op"
+	"github.com/rj45/nanogo/ir2"
+	"github.com/rj45/nanogo/sizes"
+	"github.com/rj45/nanogo/xform2"
+)
+
+var _ = xform2.Register(fieldAddrs,
+	xform2.OnlyPass(xform2.Elaboration),
+	xform2.OnOp(op.FieldAddr),
+)
+
+func fieldAddrs(it ir2.Iter) {
+	instr := it.Instr()
+
+	field, ok := ir2.IntValue(instr.Arg(0).Const())
+	if !ok {
+		panic("expected int constant")
+	}
+
+	elem := instr.Arg(1).Type.(*types.Pointer).Elem()
+	strct := elem.Underlying().(*types.Struct)
+	fieldType := strct.Field(field).Type()
+	fieldPtr := types.NewPointer(fieldType)
+
+	fields := sizes.Fieldsof(strct)
+	offsets := sizes.Offsetsof(fields)
+	offset := offsets[field]
+
+	if offset == 0 {
+		// would just be adding zero, so this instruction can just be removed
+		instr.Def(0).ReplaceUsesWith(instr.Arg(1))
+		it.Remove()
+		return
+	}
+
+	it.Update(op.Add, fieldPtr, instr.Arg(1), offset)
+}

xform2/elaboration/indexaddrs.go

@@ -0,0 +1,29 @@
+package elaboration
+
+import (
+	"go/types"
+
+	"github.com/rj45/nanogo/ir/op"
+	"github.com/rj45/nanogo/ir2"
+	"github.com/rj45/nanogo/sizes"
+	"github.com/rj45/nanogo/xform2"
+)
+
+var _ = xform2.Register(indexAddrs,
+	xform2.OnlyPass(xform2.Elaboration),
+	xform2.OnOp(op.IndexAddr),
+)
+
+// indexAddrs converts `IndexAddr` instructions into a `mul` and `add` instruction
+// The `mul` is by a constant which can be optimized into shifts and adds later.
+func indexAddrs(it ir2.Iter) {
+	instr := it.Instr()
+	elem := instr.Def(0).Type.(*types.Pointer).Elem()
+
+	size := sizes.Sizeof(elem)
+
+	mul := it.Insert(op.Mul, types.Typ[types.Int], instr.Arg(1), size)
+
+	instr.Op = op.Add
+	instr.ReplaceArg(1, mul.Def(0))
+}