From 68e76a9876a736f97c48469c546d10fdc20d4374 Mon Sep 17 00:00:00 2001
From: Ryan Culpepper <ryanc@racket-lang.org>
Date: Tue, 6 Sep 2011 02:07:01 -0600
Subject: [PATCH] =?UTF-8?q?syntax/parse:=20speed=20up=20free-identifier=3D?=
 =?UTF-8?q?=3F/phases=20when=20phases=20are=20same?=

---
 collects/syntax/parse/private/runtime.rkt | 38 +++++++++++++----------
 1 file changed, 21 insertions(+), 17 deletions(-)

diff --git a/collects/syntax/parse/private/runtime.rkt b/collects/syntax/parse/private/runtime.rkt
index d8beb8e6f0..07f8f02a9e 100644
--- a/collects/syntax/parse/private/runtime.rkt
+++ b/collects/syntax/parse/private/runtime.rkt
@@ -273,23 +273,27 @@
 ;; that y has at phase-level y.
 ;; At least one of the identifiers MUST have a binding (module or lexical)
 (define (free-identifier=?/phases x phase-x y phase-y)
-  (let ([bx (identifier-binding x phase-x)]
-        [by (identifier-binding y phase-y)])
-    (cond [(and (list? bx) (list? by))
-           (let ([modx (module-path-index-resolve (first bx))]
-                 [namex (second bx)]
-                 [phasex (fifth bx)]
-                 [mody (module-path-index-resolve (first by))]
-                 [namey (second by)]
-                 [phasey (fifth by)])
-             (and (eq? modx mody) ;; resolved-module-paths are interned
-                  (eq? namex namey)
-                  (equal? phasex phasey)))]
-          [else
-           ;; Module is only way to get phase-shift; if not module-bound names,
-           ;; then only identifiers at same phase can refer to same binding.
-           (and (equal? phase-x phase-y)
-                (free-identifier=? x y phase-x))])))
+  (cond [(eqv? phase-x phase-y)
+         (free-identifier=? x y phase-x)]
+        [else
+         (let ([bx (identifier-binding x phase-x)]
+               [by (identifier-binding y phase-y)])
+           (cond [(and (pair? bx) (pair? by))
+                  (let ([mpix (first bx)]
+                        [namex (second bx)]
+                        [defphasex (fifth bx)]
+                        [mpiy (first by)]
+                        [namey (second by)]
+                        [defphasey (fifth by)])
+                    (and (eq? namex namey)
+                         ;; resolved-module-paths are interned
+                         (eq? (module-path-index-resolve mpix)
+                              (module-path-index-resolve mpiy))
+                         (eqv? defphasex defphasey)))]
+                 [else
+                  ;; Module is only way to get phase-shift; phases differ, so
+                  ;; if not module-bound names, no way can refer to same binding.
+                  #f]))]))
 
 ;; ----