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package codegen
import (
"fmt"
"strings"
"github.com/gnolang/parscan/parser"
"github.com/gnolang/parscan/vm1"
)
type symbol struct {
index int // address of symbol in frame
local bool // if true address is relative to local frame, otherwise global
}
type Compiler struct {
Code [][]int64 // produced code, to fill VM with
Data []any // produced data, will be at the bottom of VM stack
Entry int
symbols map[string]symbol
}
func New() *Compiler { return &Compiler{symbols: map[string]symbol{}, Entry: -1} }
type nodedata struct {
ipstart, ipend, symind, fsp int // CFG and symbol node annotations
}
func (c *Compiler) CodeGen(node *parser.Node) (err error) {
notes := map[*parser.Node]*nodedata{} // AST node annotations for CFG, symbols, ...
scope := ""
frameNode := []*parser.Node{node}
fnote := notes[node]
node.Walk2(nil, 0, func(n, a *parser.Node, k int) (ok bool) {
// Node pre-order processing callback.
notes[n] = &nodedata{}
nd := notes[n]
switch n.Kind {
case parser.FuncDecl:
fname := n.Child[0].Content()
c.AddSym(len(c.Code), scope+fname, false)
scope = pushScope(scope, fname)
frameNode = append(frameNode, n)
fnote = notes[n]
for j, child := range n.Child[1].Child {
vname := child.Content()
c.AddSym(-j-2, scope+vname, true)
fnote.fsp++
}
case parser.StmtBloc:
nd.ipstart = len(c.Code)
if a != nil && a.Kind == parser.IfStmt && k == 1 {
c.Emit(n, vm1.JumpFalse, 0) // location to be updated in post IfStmt
}
}
return true
}, func(n, a *parser.Node, k int) (ok bool) {
// Node post-order processing callback.
nd := notes[n]
switch n.Kind {
case parser.AddOp:
c.Emit(n, vm1.Add)
case parser.CallExpr:
if c.isExternalSymbol(n.Child[0].Content()) {
// External call, using absolute addr in symtable
c.Emit(n, vm1.CallX, int64(len(n.Child[1].Child)))
break
}
// Internal call is always relative to instruction pointer.
i, ok := c.symInt(n.Child[0].Content())
if !ok {
err = fmt.Errorf("invalid symbol %s", n.Child[0].Content())
}
c.Emit(n, vm1.Call, int64(i-len(c.Code)))
case parser.DefOp:
// Define operation, global vars only. TODO: on local frame too
l := c.AddSym(nil, n.Child[0].Content(), false)
c.Emit(n, vm1.Assign, int64(l))
case parser.FuncDecl:
scope = popScope(scope)
fnote = notes[frameNode[len(frameNode)-1]]
case parser.Ident:
ident := n.Content()
if len(n.Child) > 0 || a.Kind == parser.FuncDecl {
break
}
if s, _, ok := c.getSym(ident, scope); ok {
if s.local {
c.Emit(n, vm1.Fdup, int64(s.index))
} else if a != nil && a.Kind == parser.AssignOp {
c.Emit(n, vm1.Push, int64(s.index))
} else if c.isExternalSymbol(ident) {
c.Emit(n, vm1.Dup, int64(s.index))
}
}
case parser.IfStmt:
ifBodyStart := notes[n.Child[1]].ipstart
ifBodyEnd := notes[n.Child[1]].ipend
c.Code[ifBodyStart][2] = int64(ifBodyEnd - ifBodyStart)
// TODO: handle 'else'
case parser.NumberLit:
// A literal number can be a float or an integer, or a big number
switch v := n.Value().(type) {
case int64:
c.Emit(n, vm1.Push, v)
case error:
err = v
return false
default:
err = fmt.Errorf("type not supported: %T\n", v)
return false
}
case parser.ReturnStmt:
fun := frameNode[len(frameNode)-1]
c.Emit(n, vm1.Return, int64(len(n.Child)), int64(len(fun.Child[1].Child)))
case parser.StmtBloc:
nd.ipend = len(c.Code)
case parser.StringLit:
p := len(c.Data)
c.Data = append(c.Data, n.Block())
c.Emit(n, vm1.Dup, int64(p))
case parser.InfOp:
c.Emit(n, vm1.Lower)
case parser.SubOp:
c.Emit(n, vm1.Sub)
}
// TODO: Fix this temporary hack to compute an entry point
if c.Entry < 0 && len(scope) == 0 && n.Kind != parser.FuncDecl {
c.Entry = len(c.Code) - 1
if c.Entry >= 0 && len(c.Code) > c.Entry && c.Code[c.Entry][1] == vm1.Return {
c.Entry++
}
}
return true
})
return
}
func (c *Compiler) AddSym(v any, name string, local bool) int {
l := len(c.Data)
if local {
l = v.(int)
} else {
c.Data = append(c.Data, v)
}
c.symbols[name] = symbol{index: l, local: local}
return l
}
func (c *Compiler) Emit(n *parser.Node, op ...int64) int {
op = append([]int64{int64(n.Pos())}, op...)
l := len(c.Code)
c.Code = append(c.Code, op)
return l
}
func (c *Compiler) isExternalSymbol(name string) bool {
s, ok := c.symbols[name]
if !ok {
return false
}
_, isInt := c.Data[s.index].(int)
return !isInt
}
func (c *Compiler) symInt(name string) (int, bool) {
s, ok := c.symbols[name]
if !ok {
return 0, false
}
j, ok := c.Data[s.index].(int)
if !ok {
return 0, false
}
return j, true
}
func pushScope(scope, name string) string {
return strings.TrimPrefix(scope+"/"+name+"/", "/")
}
func popScope(scope string) string {
scope = strings.TrimSuffix(scope, "/")
j := strings.LastIndex(scope, "/")
if j == -1 {
return ""
}
return scope[:j]
}
// getSym searches for an existing symbol starting from the deepest scope.
func (c *Compiler) getSym(name, scope string) (sym symbol, sc string, ok bool) {
for {
if sym, ok = c.symbols[scope+name]; ok {
return sym, scope, ok
}
scope = strings.TrimSuffix(scope, "/")
i := strings.LastIndex(scope, "/")
if i == -1 {
scope = ""
break
}
if scope = scope[:i]; scope == "" {
break
}
}
sym, ok = c.symbols[name]
return sym, scope, ok
}
|
