X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcompiler%2Fltv.lisp;h=e733b154ade6c0973db147b3436a65f0ef6af31a;hb=HEAD;hp=e64cc8ac81dc31915f1e5cc32ad7d45b3fd001ff;hpb=49e92ee57b3b01f5862d0c6fa65f521de1688941;p=sbcl.git

diff --git a/src/compiler/ltv.lisp b/src/compiler/ltv.lisp
index e64cc8a..e733b15 100644
--- a/src/compiler/ltv.lisp
+++ b/src/compiler/ltv.lisp
@@ -16,30 +16,71 @@
 (def-ir1-translator load-time-value
     ((form &optional read-only-p) start next result)
   #!+sb-doc
-  "Arrange for FORM to be evaluated at load-time and use the value produced
-   as if it were a constant. If READ-ONLY-P is non-NIL, then the resultant
-   object is guaranteed to never be modified, so it can be put in read-only
-   storage."
-  (let ((*allow-instrumenting* nil))
+  "Arrange for FORM to be evaluated at load-time and use the value produced as
+if it were a constant. If READ-ONLY-P is non-NIL, then the resultant object is
+guaranteed to never be modified, so it can be put in read-only storage."
+  (let ((*allow-instrumenting* nil)
+        ;; First derive an approximate type from the source form, because it allows
+        ;; us to use READ-ONLY-P implicitly.
+        ;;
+        ;; We also use this type to augment whatever COMPILE-LOAD-TIME-VALUE
+        ;; returns -- in practice it returns *WILD-TYPE* all the time, but
+        ;; theoretically it could return something useful for the READ-ONLY-P case.
+        (source-type (single-value-type
+                      (cond ((consp form)
+                             (let ((op (car form)))
+                               (cond ((member op '(the truly-the))
+                                      (values-specifier-type (second form)))
+                                     ((eq 'function op)
+                                      (specifier-type 'function))
+                                     ((and (legal-fun-name-p op)
+                                           (eq :declared (info :function :where-from op)))
+                                      (let ((ftype (info :function :type op)))
+                                        (if (fun-type-p ftype)
+                                            (fun-type-returns ftype)
+                                            *wild-type*)))
+                                     (t
+                                      *wild-type*))))
+                            ((and (symbolp form)
+                                  (eq :declared (info :variable :where-from form)))
+                             (info :variable :type form))
+                            ((constantp form)
+                             (ctype-of (eval form)))
+                            (t
+                             *universal-type*)))))
+    ;; Implictly READ-ONLY-P for immutable objects.
+    (when (and (not read-only-p)
+               (csubtypep source-type (specifier-type '(or character number))))
+      (setf read-only-p t))
     (if (producing-fasl-file)
         (multiple-value-bind (handle type)
+            ;; Value cells are allocated for non-READ-ONLY-P stop the
+            ;; compiler from complaining about constant modification
+            ;; -- it seems that we should be able to elide them all
+            ;; the time if we had a way of telling the compiler that
+            ;; "this object isn't really a constant the way you
+            ;; think". --NS 2009-06-28
             (compile-load-time-value (if read-only-p
                                          form
                                          `(make-value-cell ,form)))
-          (declare (ignore type))
-          (ir1-convert start next result
-                       (if read-only-p
-                           `(%load-time-value ',handle)
-                           `(value-cell-ref (%load-time-value ',handle)))))
-        (let ((value
-               (handler-case (eval form)
-                 (error (condition)
-                   (compiler-error "(during EVAL of LOAD-TIME-VALUE)~%~A"
-                                   condition)))))
-          (ir1-convert start next result
-                       (if read-only-p
-                           `',value
-                           `(value-cell-ref ',(make-value-cell value))))))))
+          (unless (csubtypep type source-type)
+            (setf type source-type))
+          (let ((value-form
+                  (if read-only-p
+                      `(%load-time-value ',handle)
+                      `(value-cell-ref (%load-time-value ',handle)))))
+            (the-in-policy type value-form '((type-check . 0))
+                           start next result)))
+        (let* ((value
+                 (handler-case (eval form)
+                   (error (condition)
+                     (compiler-error "(during EVAL of LOAD-TIME-VALUE)~%~A"
+                                     condition)))))
+          (if read-only-p
+              (ir1-convert start next result `',value nil)
+              (the-in-policy (ctype-of value) `(value-cell-ref ,(make-value-cell value))
+                             '((type-check . 0))
+                             start next result))))))
 
 (defoptimizer (%load-time-value ir2-convert) ((handle) node block)
   (aver (constant-lvar-p handle))