From d13e5898c8253825dd343b58d304063a10ef6d1f Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Thu, 30 Jan 2020 17:46:30 -0700
Subject: [PATCH] add `enable-unsafe-variable-reference`

original commit: 77a0ef249b6d419dcac7c8e1c28e710b30a7aa33
---
 csug/system.stex        | 11 +++++++++++
 makefiles/Mf-install.in |  2 +-
 mats/misc.ms            | 35 +++++++++++++++++++++++++++++++++++
 s/cmacros.ss            |  2 +-
 s/cpvalid.ss            |  5 ++++-
 s/front.ss              |  2 ++
 s/primdata.ss           |  1 +
 7 files changed, 55 insertions(+), 3 deletions(-)

diff --git a/csug/system.stex b/csug/system.stex
index de4d5b9c2b..46f8cb74b0 100644
--- a/csug/system.stex
+++ b/csug/system.stex
@@ -2623,6 +2623,17 @@ unsafe (i.e., no check whether the target is a procedure), even when
 the value of \scheme{optimize-level} is less than \scheme{3}. The
 default is \scheme{#f}.
 
+%----------------------------------------------------------------------------
+\entryheader
+\formdef{enable-unsafe-variable-reference}{\categorythreadparameter}{enable-unsafe-variable-reference}
+\listlibraries
+\endentryheader
+
+This parameter controls whether references to \scheme{letrec}-bound
+variables are compiled unsafe (i.e., no check whether the variable has
+a value), even when the value of \scheme{optimize-level} is less than
+\scheme{3}. The default is \scheme{#f}.
+
 %----------------------------------------------------------------------------
 \entryheader
 \formdef{generate-wpo-files}{\categorythreadparameter}{generate-wpo-files}
diff --git a/makefiles/Mf-install.in b/makefiles/Mf-install.in
index 3e876287c7..17489555e1 100644
--- a/makefiles/Mf-install.in
+++ b/makefiles/Mf-install.in
@@ -62,7 +62,7 @@ InstallLZ4Target=
 #                 no changes should be needed below this point                #
 ###############################################################################
 
-Version=csv9.5.3.15
+Version=csv9.5.3.16
 Include=boot/$m
 PetiteBoot=boot/$m/petite.boot
 SchemeBoot=boot/$m/scheme.boot
diff --git a/mats/misc.ms b/mats/misc.ms
index 76f9bb73dc..7bc5ab8d94 100644
--- a/mats/misc.ms
+++ b/mats/misc.ms
@@ -5546,6 +5546,41 @@
                              '(lambda (x) (#3%$app x))))
   )
 
+(mat enable-unsafe-variable-reference
+  (begin
+   (define (get-uncprep-form e)
+     (let ([r #f])
+       (parameterize ([run-cp0 (lambda (cp0 e)
+                                 (set! r (#%$uncprep e))
+                                 e)])
+         (expand/optimize e))
+       r))
+   #t)
+  (equivalent-expansion? (get-uncprep-form '(lambda (x) (letrec ([y y]) (+ y x))))
+                         (if (= 3 (optimize-level))
+                             '(lambda (x)
+                                (letrec ([y y])
+                                  (#3%+ y x)))
+                             '(lambda (x)
+                                (let ([valid? #f])
+                                  (letrec ([y (begin
+                                                (if valid?
+                                                    (#2%void)
+                                                    (#2%$source-violation #f #f #t "attempt to reference undefined variable ~s" 'y))
+                                                y)])
+                                    (set! valid?  #t)
+                                    (#2%+ y x))))))
+  (equivalent-expansion? (parameterize ([enable-unsafe-variable-reference #t])
+                           (get-uncprep-form '(lambda (x) (letrec ([y y]) (+ y x)))))
+                         (if (= 3 (optimize-level))
+                             '(lambda (x)
+                                (letrec ([y y])
+                                  (#3%+ y x)))
+                             '(lambda (x)
+                                (letrec ([y y])
+                                  (#2%+ y x)))))
+  )
+
 (mat phantom-bytevector
   (phantom-bytevector? (make-phantom-bytevector 0))
   (not (phantom-bytevector? 10))
diff --git a/s/cmacros.ss b/s/cmacros.ss
index ac21c185de..a3846d7a64 100644
--- a/s/cmacros.ss
+++ b/s/cmacros.ss
@@ -328,7 +328,7 @@
                  [(_ foo e1 e2) e1] ...
                  [(_ bar e1 e2) e2]))))])))
 
-(define-constant scheme-version #x0905030F)
+(define-constant scheme-version #x09050310)
 
 (define-syntax define-machine-types
   (lambda (x)
diff --git a/s/cpvalid.ss b/s/cpvalid.ss
index 35734dca0d..3b63f5cb54 100644
--- a/s/cpvalid.ss
+++ b/s/cpvalid.ss
@@ -568,4 +568,7 @@
 
   (set! $cpvalid
     (lambda (x)
-      (if (= (optimize-level) 3) x (cpvalid x)))))
+      (if (or (= (optimize-level) 3)
+              (enable-unsafe-variable-reference))
+          x
+          (cpvalid x)))))
diff --git a/s/front.ss b/s/front.ss
index d647b7a248..402973f8dc 100644
--- a/s/front.ss
+++ b/s/front.ss
@@ -108,6 +108,8 @@
 
 (define enable-unsafe-application ($make-thread-parameter #f (lambda (x) (and x #t))))
 
+(define enable-unsafe-variable-reference ($make-thread-parameter #f (lambda (x) (and x #t))))
+
 (define-who current-generate-id
   ($make-thread-parameter
    (lambda (sym)
diff --git a/s/primdata.ss b/s/primdata.ss
index b280ee5cf1..bc41a5e55a 100644
--- a/s/primdata.ss
+++ b/s/primdata.ss
@@ -959,6 +959,7 @@
   (enable-type-recovery [sig [() -> (boolean)] [(ptr) -> (void)]] [flags unrestricted])
   (enable-error-source-expression [sig [() -> (boolean)] [(ptr) -> (void)]] [flags unrestricted])
   (enable-unsafe-application [sig [() -> (boolean)] [(ptr) -> (void)]] [flags unrestricted])
+  (enable-unsafe-variable-reference [sig [() -> (boolean)] [(ptr) -> (void)]] [flags unrestricted])
   (eval-syntax-expanders-when [sig [() -> (list)] [(sub-list) -> (void)]] [flags])
   (expand-omit-library-invocations [sig [() -> (boolean)] [(ptr) -> (void)]] [flags unrestricted])
   (expand-output [sig [() -> (maybe-textual-output-port)] [(maybe-textual-output-port) -> (void)]] [flags])