From ea31bac351e90cd4c8d502bdb55d12df86d16c15 Mon Sep 17 00:00:00 2001
From: John Lorentzson <john_lorentzson@yahoo.com>
Date: Wed, 9 Jul 2025 13:30:20 +0200
Subject: [PATCH] Fix compilation of loops with variable as stop value

It was previously decided that, since the language is not to be
Turing-complete, a loop that takes a variable for its upper bound
should use the variable's value at the time of the loop's start, not
look it up. I forgot this while writing the syntax->IR compiler, so
loops with non-constant stop counts failed to compile.
---
 .../middle/compile-node-to-ir.lisp            | 38 +++++++++++++------
 1 file changed, 26 insertions(+), 12 deletions(-)

diff --git a/wip-duuqnd/user-side-compiler/middle/compile-node-to-ir.lisp b/wip-duuqnd/user-side-compiler/middle/compile-node-to-ir.lisp
index e29b1d9..ebbbb41 100644
--- a/wip-duuqnd/user-side-compiler/middle/compile-node-to-ir.lisp
+++ b/wip-duuqnd/user-side-compiler/middle/compile-node-to-ir.lisp
@@ -91,14 +91,27 @@
     (build-begin builder continuation)))
 
 (defmethod compile-node ((node node-dotimes) builder)
-  (unless (zerop (ref-value (stop-ref node)))
-    (let ((const-zero (make-instance 'ir-constant))
-          (const-stop (make-instance 'ir-constant))
-          (loop-body (make-instance 'iblock :name "loop"))
-          (continuation (make-instance 'iblock :name "after_loop"))
-          (counter-variable (find-variable (counter-ref node) builder))
-          
-          (test-result (make-instance 'ir-result)))
+  (unless (and (typep (stop-ref node) 'reference-constant)
+               (zerop (ref-value (stop-ref node))))
+    (let* ((stop-ref-const-p (typep (stop-ref node) 'reference-constant))
+           (const-zero (make-instance 'ir-constant))
+           (const-stop (if stop-ref-const-p
+                           (make-instance 'ir-constant)
+                           (make-instance 'ir-result)))
+           (loop-body (make-instance 'iblock :name "loop"))
+           (continuation (make-instance 'iblock :name "after_loop"))
+           (counter-variable (find-variable (counter-ref node) builder))
+           (test-result (make-instance 'ir-result)))
+      (unless stop-ref-const-p
+        (let ((zero (make-instance 'ir-constant)))
+          (build-insert (make-instance 'ir-getconst :input 0 :output zero)
+                        builder)
+          (build-insert (make-instance
+                         'ir-plus
+                         :inputs (list (compile-node (stop-ref node) builder)
+                                       zero)
+                         :output const-stop)
+                        builder)))
       (build-insert (make-instance 'ir-getconst
                                    :input 0 :output const-zero)
                     builder)
@@ -138,10 +151,11 @@
                                      :input counter-variable
                                      :output counter-value)
                       builder)
-        (build-insert (make-instance 'ir-getconst
-                                     :input (ref-value (stop-ref node))
-                                     :output const-stop)
-                      builder)
+        (when stop-ref-const-p
+          (build-insert (make-instance 'ir-getconst
+                                       :input (ref-value (stop-ref node))
+                                       :output const-stop)
+                        builder))
         (build-insert (make-instance 'ir-test-equal
                                      :inputs (list counter-value const-stop)
                                      :output test-result)