Replace the C1 processor for COERCE with a compiler macro that is now activated, and in this case add a new coercion function for simple arrays.

src/cmp/cmpfun.lsp

@@ -318,6 +318,5 @@
 (put-sysprop 'nth 'C1CONDITIONAL 'co1nth)
 (put-sysprop 'nthcdr 'C1CONDITIONAL 'co1nthcdr)
 
-(put-sysprop 'coerce 'C1CONDITIONAL 'co1coerce)
 (put-sysprop 'cons 'C1CONDITIONAL 'co1cons)
 (put-sysprop 'ldb 'C1CONDITIONAL 'co1ldb)

src/cmp/cmpopt.lsp

@@ -226,7 +226,7 @@
 	   (cmperror "Cannot COERCE an expression to an empty type."))
 	  ;;
 	  ;; No optimizations that take up too much space unless requested.
-	  ((policy-inline-type-checks)
+	  ((not (policy-inline-type-checks))
 	   form)
 	  ;;
 	  ;; Search for a simple template above, replacing X by the value.
@@ -265,7 +265,8 @@
 	       (si::closest-sequence-type type)
 	     (if (eq elt-type 'list)
 		 `(si::coerce-to-list ,value)
-		 `(si::coerce-to-vector ,value ',elt-type ',length))))
+		 `(si::coerce-to-vector ,value ',elt-type ',length
+                                        ,(and (subtypep type 'simple-array) t)))))
 	  ;;
 	  ;; There are no other atomic types to optimize
 	  ((atom type)

src/lsp/seq.lsp

@@ -160,9 +160,10 @@ default value of INITIAL-ELEMENT depends on TYPE."
 	  ((null it) (nreverse output))
 	(push (seq-iterator-ref object it) output))))
 
-(defun coerce-to-vector (object elt-type length)
+(defun coerce-to-vector (object elt-type length simple-array-p)
   (let ((output object))
     (unless (and (vectorp object)
+                 (or (null simple-array-p) (simple-array-p object))
 		 (eq (array-element-type object) elt-type))
       (let* ((final-length (if (eq length '*) (length object) length)))
 	(setf output (make-vector elt-type final-length nil nil nil 0))