Insert fixed-to-multiple in optimizations to preserve semantics

Without this, optimization leads to alien behavior like
((lambda (x) x) (values 1 2 3)) => 1 2 3 (instead of 1)

BIR-transformations/interpolate-function.lisp

@@ -100,13 +100,25 @@
       ;; The stuff in the AFTER block is now unreachable.
       (cleavir-bir:delete-iblock after)
       (let ((call-arguments (rest (cleavir-bir:inputs call)))
+            (ftmd-arguments
+              (loop for datum in (rest (cleavir-bir:inputs call))
+                    collect (make-instance 'cleavir-bir:output
+                              :name (cleavir-bir:name datum)
+                              :derived-type (cleavir-bir:ctype datum))))
             (inputs '()))
         ;; Remove the local call.
         (cleavir-bir:delete-instruction call)
+        ;; Insert fixed-to-multiple instructions to ensure only primary values
+        ;; of the call arguments are used.
+        (loop for arg in call-arguments for ftm-out in ftmd-arguments
+              for ftm = (make-instance 'cleavir-bir:fixed-to-multiple
+                          :inputs (list arg) :outputs (list ftm-out))
+              do (cleavir-bir:insert-instruction-before ftm jump))
+        ;; Compute inputs to the jump.
         (cleavir-bir:map-lambda-list
          (lambda (state item index)
            (declare (ignore index))
-           (let ((arg (pop call-arguments)))
+           (let ((arg (pop ftmd-arguments)))
              (ecase state
                (:required
                 (push arg inputs))

BIR-transformations/meta-evaluate.lisp

@@ -371,9 +371,14 @@
                   (cleavir-bir:function reader))
           #+(or)
           (format t "~&meta-evaluate: substituting single read binding of ~a" variable)
-          (let ((input (cleavir-bir:input binder)))
+          (let* ((input (cleavir-bir:input binder))
+                 (fout (make-instance 'cleavir-bir:output))
+                 (ftm (make-instance 'cleavir-bir:fixed-to-multiple
+                        :outputs (list fout))))
             (setf (cleavir-bir:inputs binder) nil)
-            (cleavir-bir:replace-uses input reader-out))
+            (cleavir-bir:insert-instruction-before ftm reader)
+            (cleavir-bir:replace-uses fout reader-out)
+            (setf (cleavir-bir:inputs ftm) (list input)))
           (cleavir-bir:delete-instruction reader)
           t)))))