Changed COMPUTE-KEY-HASH to compute hash value optimistically and only

go into the SET-INTERRUPT-ENABLES! guarded loop if, as a post-check,
the table needs rehashing.

On a test case (the new compiler on list.scm) this reduces the
profiled time in SET-INTERRUPT-ENABLES! from 9.9% to 3.4%

diff --git a/v7/src/runtime/hashtb.scm b/v7/src/runtime/hashtb.scm
index e9387f38eb9ecf3ac2244dca0372280639bc8b46..c11e9cb13965ab7243c498350acfd1807eccb069 100644 (file)
--- a/v7/src/runtime/hashtb.scm
+++ b/v7/src/runtime/hashtb.scm
@@ -1,8 +1,8 @@
 #| -*-Scheme-*-
 
-$Id: hashtb.scm,v 1.20 1994/10/28 05:58:22 jawilson Exp $
+$Id: hashtb.scm,v 1.21 1995/04/30 15:09:15 adams Exp $
 
-Copyright (c) 1990-94 Massachusetts Institute of Technology
+Copyright (c) 1990-1995 Massachusetts Institute of Technology
 
 This material was developed by the Scheme project at the Massachusetts
 Institute of Technology, Department of Electrical Engineering and
@@ -688,20 +688,24 @@ MIT in each case. |#
 (define (compute-key-hash table key)
   (let ((key-hash (table-key-hash table)))
     (if (table-rehash-after-gc? table)
-       (let ((interrupt-mask (set-interrupt-enables! interrupt-mask/none)))
-         (let loop ()
-           (if (table-needs-rehash? table)
-               (begin
+       (let ((hash (key-hash key (vector-length (table-buckets table)))))
+         (if (not (table-needs-rehash? table))
+             hash
+             (let ((interrupt-mask
+                    (set-interrupt-enables! interrupt-mask/none)))
+               (let loop ()
                  (rehash-table! table)
                  (if (< (table-count table) (table-shrink-size table))
                      (begin
                        (set-interrupt-enables! interrupt-mask/gc-ok)
                        (shrink-table! table)
                        (set-interrupt-enables! interrupt-mask/none)
-                       (loop))))))
-         (let ((hash (key-hash key (vector-length (table-buckets table)))))
-           (set-interrupt-enables! interrupt-mask)
-           hash))
+                       (if (table-needs-rehash? table)
+                           (loop)))))
+               (let ((hash
+                      (key-hash key (vector-length (table-buckets table)))))
+                 (set-interrupt-enables! interrupt-mask)
+                 hash))))
        (key-hash key (vector-length (table-buckets table))))))
 \f
 (define-integrable (eq-hash-mod key modulus)