From 2837dabf7818666a9366d659d2da3b9055140740 Mon Sep 17 00:00:00 2001
From: Marc Vertes <mvertes@free.fr>
Date: Fri, 23 Jan 2026 11:16:12 +0100
Subject: feat: make Next iterator instruction faster and more efficient

Branching control is delegated directly to the Next instruction,
which now takes the location of loop exit as first argument.
It avoids the use of JumpFalse, plus the stack storage for the
condition.
---
 parser/parse.go | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

(limited to 'parser/parse.go')

diff --git a/parser/parse.go b/parser/parse.go
index daf30ca..e72e16e 100644
--- a/parser/parse.go
+++ b/parser/parse.go
@@ -201,6 +201,7 @@ func (p *Parser) parseGoto(in Tokens) (out Tokens, err error) {
 func (p *Parser) parseFor(in Tokens) (out Tokens, err error) {
 	// TODO: detect invalid code.
 	var init, cond, post, body, final Tokens
+	hasRange := in.Index(lang.Range) >= 0
 	fc := strconv.Itoa(p.labelCount[p.scope])
 	p.labelCount[p.scope]++
 	breakLabel, continueLabel := p.breakLabel, p.continueLabel
@@ -213,10 +214,10 @@ func (p *Parser) parseFor(in Tokens) (out Tokens, err error) {
 	pre := in[1 : len(in)-1].Split(lang.Semicolon)
 	switch len(pre) {
 	case 1:
-		if in.Index(lang.Range) >= 0 {
+		if hasRange {
 			init = pre[0]
-			cond = Tokens{{Token: scanner.Token{Tok: lang.Next}}}
-			final = Tokens{{Token: scanner.Token{Tok: lang.Stop}}}
+			cond = Tokens{newNext(p.breakLabel, in[1].Pos)}
+			final = Tokens{newStop(in[1].Pos)}
 		} else {
 			cond = pre[0]
 		}
@@ -231,13 +232,15 @@ func (p *Parser) parseFor(in Tokens) (out Tokens, err error) {
 		}
 		out = init
 	}
-	out = append(out, newLabel(p.scope+"b", in[0].Pos))
+	out = append(out, newLabel(p.continueLabel, in[0].Pos))
 	if len(cond) > 0 {
 		if cond, err = p.parseExpr(cond, ""); err != nil {
 			return nil, err
 		}
 		out = append(out, cond...)
-		out = append(out, newJumpFalse(p.scope+"e", in[0].Pos))
+		if !hasRange {
+			out = append(out, newJumpFalse(p.breakLabel, in[0].Pos))
+		}
 	}
 	if body, err = p.Parse(in[len(in)-1].Block()); err != nil {
 		return nil, err
@@ -250,8 +253,8 @@ func (p *Parser) parseFor(in Tokens) (out Tokens, err error) {
 		out = append(out, post...)
 	}
 	out = append(out,
-		newGoto(p.scope+"b", in[0].Pos),
-		newLabel(p.scope+"e", in[0].Pos),
+		newGoto(p.continueLabel, in[0].Pos),
+		newLabel(p.breakLabel, in[0].Pos),
 	)
 	out = append(out, final...)
 	return out, err
-- 
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