Fix broken IR graph flow with merge iblocks

wip-duuqnd/user-side-compiler/middle/compile-node-to-ir.lisp

@@ -74,7 +74,7 @@
          (then-iblock (make-instance 'iblock :name "then"))
          (else-iblock (make-instance 'iblock :name "else"))
          (continuation (if else-exists-p
-                           (make-instance 'iblock :name "merge")
+                           (make-instance 'iblock-merge :name "merge")
                            else-iblock)))
     (build-insert-end (make-instance
                        'ir-if

wip-duuqnd/user-side-compiler/middle/jigs.lisp

@@ -40,19 +40,33 @@
 
 ;;; Compilation setup
 
-(defun fix-iblock-flow (iblock)
-  (let ((reached '()))
+(defun fix-iblock-flow (start-iblock)
+  (let ((reached '())
+        (last nil)
+        (deferred '()))
     (labels
-        ((fix (iblock prev)
+        ((fix-deferred ()
+           (unless (null deferred)
+             (loop :for after :in (nreverse (pop deferred))
+                   :do (fix after last))))
+         (fix (iblock prev)
            (unless (member iblock reached)
              (push iblock reached)
-             (setf (next iblock)
-                   (first (successors iblock))
-                   (prev iblock) prev)
-             (loop :for prev := iblock :then s
-                   :for s :in (successors iblock)
-                   :do (fix s prev)))))
-      (fix iblock nil))))
+             (unless (null prev)
+               (setf (next prev) iblock))
+             (setf (prev iblock) prev
+                   last iblock)
+             (fix-deferred)
+             (push '() deferred)
+             (loop :for s :in (successors iblock)
+                   :if (typep s 'iblock-merge)
+                     :do (pushnew s (car deferred))
+                   :else
+                     :do (fix s last))
+             (when (null prev)
+               (loop :until (null deferred)
+                     :do (fix-deferred))))))
+      (fix start-iblock nil))))
 
 (defmacro with-compilation-setup ((iblock builder &key add-return-p) &body body)
   `(let ((,iblock (make-instance 'iblock :name "toplevel" :program (make-instance 'ir-program)))

wip-duuqnd/user-side-compiler/middle/structure.lisp

@@ -12,6 +12,8 @@
    (%prev :accessor prev :type (or null iblock) :initform nil)
    (%name :accessor name :initarg :name :initform nil)))
 
+(defclass iblock-merge (iblock) ())
+
 (defmethod find-variable (reference (search-from ir-program))
   (multiple-value-bind (var existsp)
       (gethash reference (variables search-from))