From 5400b41bce4ad6a4430098a0a35e468360b8e6fd Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Tue, 13 Nov 2012 10:23:04 -0700
Subject: [PATCH] add `unsafe-cons-pair'

Also, make `list?' more optimistic about checking is  the "is list?"
flag on a pair.
---
 collects/scribblings/reference/unsafe.scrbl |   6 +
 doc/release-notes/racket/HISTORY.txt        |   3 +
 src/racket/include/mzwin.def                |   1 +
 src/racket/include/mzwin3m.def              |   1 +
 src/racket/include/racket.exp               |   1 +
 src/racket/include/racket3m.exp             |   1 +
 src/racket/src/cstartup.inc                 | 191 ++++++++++----------
 src/racket/src/jit.h                        |   4 +-
 src/racket/src/jitcommon.c                  |   2 +-
 src/racket/src/jitinline.c                  |  95 +++++++---
 src/racket/src/list.c                       |  62 +++++--
 src/racket/src/optimize.c                   |   5 +-
 src/racket/src/schemef.h                    |   1 +
 src/racket/src/schemex.h                    |   1 +
 src/racket/src/schemex.inc                  |   1 +
 src/racket/src/schemexm.h                   |   1 +
 src/racket/src/schminc.h                    |   2 +-
 src/racket/src/schpriv.h                    |   1 +
 src/racket/src/schvers.h                    |   4 +-
 19 files changed, 241 insertions(+), 142 deletions(-)

diff --git a/collects/scribblings/reference/unsafe.scrbl b/collects/scribblings/reference/unsafe.scrbl
index 29ad00ec32..165a5b8833 100644
--- a/collects/scribblings/reference/unsafe.scrbl
+++ b/collects/scribblings/reference/unsafe.scrbl
@@ -192,6 +192,12 @@ Unsafe variants of @racket[car], @racket[cdr], @racket[mcar],
 @racket[mcdr], @racket[set-mcar!], and @racket[set-mcdr!].}
 
 
+@defproc[(unsafe-cons [v any/c] [rest list?]) (and/c pair? list?)]{
+
+Unsafe variant of @racket[cons] that produces a pair that claims to be
+a list---without checking whether @racket[rest] is a list.}
+
+
 @deftogether[(
 @defproc[(unsafe-list-ref [lst pair?] [pos (and/c exact-nonnegative-integer? fixnum?)]) any/c]
 @defproc[(unsafe-list-tail [lst any/c] [pos (and/c exact-nonnegative-integer? fixnum?)]) any/c]
diff --git a/doc/release-notes/racket/HISTORY.txt b/doc/release-notes/racket/HISTORY.txt
index 5cf717187d..10cd4a83e4 100644
--- a/doc/release-notes/racket/HISTORY.txt
+++ b/doc/release-notes/racket/HISTORY.txt
@@ -1,3 +1,6 @@
+Version 5.3.1.6
+racket/unsafe/ops: added unsafe-cons-list
+
 Version 5.3.1.5
 racket/gui: added get-current-mouse-state
 
diff --git a/src/racket/include/mzwin.def b/src/racket/include/mzwin.def
index c2ca31989d..cb266a247e 100644
--- a/src/racket/include/mzwin.def
+++ b/src/racket/include/mzwin.def
@@ -271,6 +271,7 @@ EXPORTS
  scheme_prim_is_method
  scheme_make_pair
  scheme_make_mutable_pair
+ scheme_make_list_pair
  scheme_make_raw_pair
  scheme_make_byte_string
  scheme_make_sized_byte_string
diff --git a/src/racket/include/mzwin3m.def b/src/racket/include/mzwin3m.def
index 14d32513ce..d91c8da937 100644
--- a/src/racket/include/mzwin3m.def
+++ b/src/racket/include/mzwin3m.def
@@ -286,6 +286,7 @@ EXPORTS
  scheme_prim_is_method
  scheme_make_pair
  scheme_make_mutable_pair
+ scheme_make_list_pair
  scheme_make_raw_pair
  scheme_make_byte_string
  scheme_make_sized_byte_string
diff --git a/src/racket/include/racket.exp b/src/racket/include/racket.exp
index 96a6ec3778..5afc5c6a5e 100644
--- a/src/racket/include/racket.exp
+++ b/src/racket/include/racket.exp
@@ -288,6 +288,7 @@ scheme_make_closed_prim_w_everything
 scheme_prim_is_method
 scheme_make_pair
 scheme_make_mutable_pair
+scheme_make_list_pair
 scheme_make_raw_pair
 scheme_make_byte_string
 scheme_make_sized_byte_string
diff --git a/src/racket/include/racket3m.exp b/src/racket/include/racket3m.exp
index b45f182381..3a5be64751 100644
--- a/src/racket/include/racket3m.exp
+++ b/src/racket/include/racket3m.exp
@@ -294,6 +294,7 @@ scheme_make_closed_prim_w_everything
 scheme_prim_is_method
 scheme_make_pair
 scheme_make_mutable_pair
+scheme_make_list_pair
 scheme_make_raw_pair
 scheme_make_byte_string
 scheme_make_sized_byte_string
diff --git a/src/racket/src/cstartup.inc b/src/racket/src/cstartup.inc
index 769f9e02b5..ef10ea5f1b 100644
--- a/src/racket/src/cstartup.inc
+++ b/src/racket/src/cstartup.inc
@@ -1,5 +1,5 @@
   {
-    SHARED_OK static MZCOMPILED_STRING_FAR unsigned char expr[] = {35,126,7,53,46,51,46,49,46,53,84,0,0,0,0,0,0,0,0,0,0,
+    SHARED_OK static MZCOMPILED_STRING_FAR unsigned char expr[] = {35,126,7,53,46,51,46,49,46,54,84,0,0,0,0,0,0,0,0,0,0,
 0,0,0,0,0,0,0,0,0,0,51,0,0,0,1,0,0,10,0,14,0,
 21,0,28,0,33,0,37,0,40,0,45,0,58,0,62,0,67,0,74,0,83,
 0,87,0,93,0,107,0,121,0,124,0,130,0,134,0,136,0,147,0,149,0,
@@ -27,32 +27,32 @@
 248,22,106,201,27,248,22,163,4,195,249,22,156,4,80,158,39,36,251,22,89,
 2,18,248,22,104,199,249,22,79,2,19,248,22,106,201,12,27,248,22,81,248,
 22,163,4,196,28,248,22,87,193,20,14,159,37,36,37,28,248,22,87,248,22,
-81,194,248,22,163,17,193,249,22,156,4,80,158,39,36,251,22,89,2,18,248,
-22,163,17,199,249,22,79,2,6,248,22,164,17,201,11,18,100,10,13,16,6,
+81,194,248,22,164,17,193,249,22,156,4,80,158,39,36,251,22,89,2,18,248,
+22,164,17,199,249,22,79,2,6,248,22,165,17,201,11,18,100,10,13,16,6,
 36,2,14,2,2,11,11,11,8,32,8,31,8,30,8,29,16,4,11,11,2,
 20,3,1,8,101,110,118,49,55,51,51,57,16,4,11,11,2,21,3,1,8,
 101,110,118,49,55,51,52,48,27,248,22,81,248,22,163,4,196,28,248,22,87,
-193,20,14,159,37,36,37,28,248,22,87,248,22,81,194,248,22,163,17,193,249,
+193,20,14,159,37,36,37,28,248,22,87,248,22,81,194,248,22,164,17,193,249,
 22,156,4,80,158,39,36,250,22,89,2,22,248,22,89,249,22,89,248,22,89,
-2,23,248,22,163,17,201,251,22,89,2,18,2,23,2,23,249,22,79,2,7,
-248,22,164,17,204,18,100,11,13,16,6,36,2,14,2,2,11,11,11,8,32,
+2,23,248,22,164,17,201,251,22,89,2,18,2,23,2,23,249,22,79,2,7,
+248,22,165,17,204,18,100,11,13,16,6,36,2,14,2,2,11,11,11,8,32,
 8,31,8,30,8,29,16,4,11,11,2,20,3,1,8,101,110,118,49,55,51,
 52,50,16,4,11,11,2,21,3,1,8,101,110,118,49,55,51,52,51,248,22,
 163,4,193,27,248,22,163,4,194,249,22,79,248,22,89,248,22,80,196,248,22,
-164,17,195,27,248,22,81,248,22,163,4,23,197,1,249,22,156,4,80,158,39,
+165,17,195,27,248,22,81,248,22,163,4,23,197,1,249,22,156,4,80,158,39,
 36,28,248,22,64,248,22,157,4,248,22,80,23,198,2,27,249,22,2,32,0,
 88,163,8,36,37,43,11,9,222,33,40,248,22,163,4,248,22,104,23,200,2,
-250,22,89,2,24,248,22,89,249,22,89,248,22,89,248,22,163,17,23,204,2,
+250,22,89,2,24,248,22,89,249,22,89,248,22,89,248,22,164,17,23,204,2,
 250,22,90,2,25,249,22,2,22,80,23,204,2,248,22,106,23,206,2,249,22,
-79,248,22,163,17,23,202,1,249,22,2,22,104,23,200,1,250,22,90,2,22,
+79,248,22,164,17,23,202,1,249,22,2,22,104,23,200,1,250,22,90,2,22,
 249,22,2,32,0,88,163,8,36,37,47,11,9,222,33,41,248,22,163,4,248,
-22,163,17,201,248,22,164,17,198,27,248,22,163,4,194,249,22,79,248,22,89,
-248,22,80,196,248,22,164,17,195,27,248,22,81,248,22,163,4,23,197,1,249,
+22,164,17,201,248,22,165,17,198,27,248,22,163,4,194,249,22,79,248,22,89,
+248,22,80,196,248,22,165,17,195,27,248,22,81,248,22,163,4,23,197,1,249,
 22,156,4,80,158,39,36,250,22,90,2,24,249,22,2,32,0,88,163,8,36,
-37,47,11,9,222,33,43,248,22,163,4,248,22,80,201,248,22,164,17,198,27,
+37,47,11,9,222,33,43,248,22,163,4,248,22,80,201,248,22,165,17,198,27,
 248,22,81,248,22,163,4,196,27,248,22,163,4,248,22,80,195,249,22,156,4,
 80,158,40,36,28,248,22,87,195,250,22,90,2,22,9,248,22,81,199,250,22,
-89,2,10,248,22,89,248,22,80,199,250,22,90,2,5,248,22,164,17,201,248,
+89,2,10,248,22,89,248,22,80,199,250,22,90,2,5,248,22,165,17,201,248,
 22,81,202,27,248,22,81,248,22,163,4,23,197,1,27,249,22,1,22,93,249,
 22,2,22,163,4,248,22,163,4,248,22,80,199,248,22,183,4,249,22,156,4,
 80,158,41,36,251,22,89,1,22,119,105,116,104,45,99,111,110,116,105,110,117,
@@ -65,15 +65,15 @@
 9,62,61,62,248,22,157,4,248,22,104,196,250,22,89,2,22,248,22,89,249,
 22,89,21,93,2,27,248,22,80,199,250,22,90,2,11,249,22,89,2,27,249,
 22,89,248,22,113,203,2,27,248,22,81,202,251,22,89,2,18,28,249,22,152,
-9,248,22,157,4,248,22,80,200,64,101,108,115,101,10,248,22,163,17,197,250,
-22,90,2,22,9,248,22,164,17,200,249,22,79,2,11,248,22,81,202,99,13,
+9,248,22,157,4,248,22,80,200,64,101,108,115,101,10,248,22,164,17,197,250,
+22,90,2,22,9,248,22,165,17,200,249,22,79,2,11,248,22,81,202,99,13,
 16,6,36,2,14,2,2,11,11,11,8,32,8,31,8,30,8,29,16,4,11,
 11,2,20,3,1,8,101,110,118,49,55,51,54,53,16,4,11,11,2,21,3,
 1,8,101,110,118,49,55,51,54,54,18,158,94,10,64,118,111,105,100,8,48,
 27,248,22,81,248,22,163,4,196,249,22,156,4,80,158,39,36,28,248,22,64,
-248,22,157,4,248,22,80,197,250,22,89,2,28,248,22,89,248,22,163,17,199,
-248,22,104,198,27,248,22,157,4,248,22,163,17,197,250,22,89,2,28,248,22,
-89,248,22,80,197,250,22,90,2,25,248,22,164,17,199,248,22,164,17,202,159,
+248,22,157,4,248,22,80,197,250,22,89,2,28,248,22,89,248,22,164,17,199,
+248,22,104,198,27,248,22,157,4,248,22,164,17,197,250,22,89,2,28,248,22,
+89,248,22,80,197,250,22,90,2,25,248,22,165,17,199,248,22,165,17,202,159,
 36,20,113,159,36,16,1,11,16,0,20,26,149,9,2,1,2,1,2,2,9,
 9,11,11,11,10,36,80,158,36,36,20,113,159,36,16,0,16,0,38,39,36,
 16,0,36,16,0,36,11,11,11,16,10,2,3,2,4,2,5,2,6,2,7,
@@ -100,7 +100,7 @@
     EVAL_ONE_SIZED_STR((char *)expr, 2048);
   }
   {
-    SHARED_OK static MZCOMPILED_STRING_FAR unsigned char expr[] = {35,126,7,53,46,51,46,49,46,53,84,0,0,0,0,0,0,0,0,0,0,
+    SHARED_OK static MZCOMPILED_STRING_FAR unsigned char expr[] = {35,126,7,53,46,51,46,49,46,54,84,0,0,0,0,0,0,0,0,0,0,
 0,0,0,0,0,0,0,0,0,0,126,0,0,0,1,0,0,8,0,21,0,
 26,0,43,0,55,0,77,0,106,0,121,0,139,0,151,0,167,0,181,0,203,
 0,219,0,236,0,2,1,13,1,19,1,28,1,35,1,42,1,54,1,70,1,
@@ -343,7 +343,7 @@
 115,105,111,110,248,22,191,5,193,28,248,22,88,23,194,2,28,28,249,22,191,
 3,38,248,22,92,23,196,2,10,249,22,191,3,39,248,22,92,23,196,2,28,
 28,248,22,142,7,248,22,80,23,195,2,10,249,22,152,9,64,114,111,111,116,
-248,22,163,17,23,196,2,28,27,248,22,104,194,28,248,22,184,14,23,194,2,
+248,22,164,17,23,196,2,28,27,248,22,104,194,28,248,22,184,14,23,194,2,
 10,28,248,22,142,7,23,194,2,28,248,22,142,15,23,194,2,10,248,22,143,
 15,23,194,1,11,27,248,22,87,248,22,106,195,28,192,192,248,22,186,15,248,
 22,113,195,11,11,11,11,250,22,158,2,196,197,249,22,79,197,200,28,28,248,
@@ -351,7 +351,7 @@
 160,8,27,248,22,147,15,249,22,145,15,248,22,104,23,200,2,23,198,1,28,
 248,22,64,248,22,80,23,198,2,86,94,23,196,1,86,94,28,250,22,160,2,
 196,11,11,12,250,22,158,2,196,11,9,249,22,164,2,195,88,163,8,36,38,
-50,11,9,224,3,2,33,94,27,248,22,67,248,22,163,17,23,199,1,250,22,
+50,11,9,224,3,2,33,94,27,248,22,67,248,22,164,17,23,199,1,250,22,
 158,2,23,198,2,23,196,2,249,22,79,248,22,131,2,23,200,1,250,22,160,
 2,23,203,1,23,201,1,9,12,250,22,158,2,195,196,248,22,94,198,20,13,
 159,80,159,37,58,37,88,163,36,37,54,8,240,0,144,0,0,9,225,1,0,
@@ -392,11 +392,11 @@
 102,88,163,8,36,37,47,11,2,41,222,33,105,32,103,88,163,36,37,43,11,
 69,116,111,45,115,116,114,105,110,103,222,33,104,28,248,22,184,14,193,248,22,
 188,14,193,192,28,248,22,87,248,22,81,23,195,2,248,22,89,248,2,103,248,
-22,163,17,23,196,1,250,22,90,248,2,103,248,22,163,17,23,198,2,2,50,
-248,2,102,248,22,164,17,23,198,1,249,22,190,7,2,51,194,32,107,88,163,
+22,164,17,23,196,1,250,22,90,248,2,103,248,22,164,17,23,198,2,2,50,
+248,2,102,248,22,165,17,23,198,1,249,22,190,7,2,51,194,32,107,88,163,
 36,38,48,11,66,102,105,108,116,101,114,222,33,108,28,248,22,87,23,195,2,
-9,28,248,23,194,2,248,22,80,23,196,2,249,22,79,248,22,163,17,23,197,
-2,249,2,107,23,197,1,248,22,164,17,23,199,1,249,2,107,194,248,22,164,
+9,28,248,23,194,2,248,22,80,23,196,2,249,22,79,248,22,164,17,23,197,
+2,249,2,107,23,197,1,248,22,165,17,23,199,1,249,2,107,194,248,22,165,
 17,196,249,22,190,7,2,51,248,22,134,2,23,196,1,28,248,22,87,23,199,
 2,86,94,23,198,1,28,23,199,2,28,196,249,22,138,15,200,198,198,27,28,
 248,22,87,23,197,2,2,49,249,22,1,22,165,7,248,2,102,23,199,2,248,
@@ -581,34 +581,37 @@
     EVAL_ONE_SIZED_STR((char *)expr, 10019);
   }
   {
-    SHARED_OK static MZCOMPILED_STRING_FAR unsigned char expr[] = {35,126,7,53,46,51,46,49,46,53,84,0,0,0,0,0,0,0,0,0,0,
-0,0,0,0,0,0,0,0,0,0,12,0,0,0,1,0,0,15,0,40,0,
-57,0,75,0,97,0,120,0,140,0,162,0,169,0,176,0,183,0,0,0,179,
-1,0,0,74,35,37,112,108,97,99,101,45,115,116,114,117,99,116,1,23,115,
-116,114,117,99,116,58,84,72,45,112,108,97,99,101,45,99,104,97,110,110,101,
-108,76,84,72,45,112,108,97,99,101,45,99,104,97,110,110,101,108,77,84,72,
-45,112,108,97,99,101,45,99,104,97,110,110,101,108,63,1,20,84,72,45,112,
-108,97,99,101,45,99,104,97,110,110,101,108,45,114,101,102,1,21,84,72,45,
-112,108,97,99,101,45,99,104,97,110,110,101,108,45,115,101,116,33,79,84,72,
-45,112,108,97,99,101,45,99,104,97,110,110,101,108,45,105,110,1,20,84,72,
-45,112,108,97,99,101,45,99,104,97,110,110,101,108,45,111,117,116,249,80,158,
-38,39,195,36,249,80,158,38,39,195,36,249,80,158,38,39,195,37,159,36,20,
-113,159,36,16,1,11,16,0,20,26,144,9,2,1,2,1,29,11,11,11,9,
-9,11,11,11,10,45,80,158,36,36,20,113,159,36,16,7,2,2,2,3,2,
-4,2,5,2,6,2,7,2,8,16,0,37,39,36,16,0,36,16,2,2,5,
-2,6,38,11,11,11,16,5,2,3,2,7,2,8,2,4,2,2,16,5,11,
-11,11,11,11,16,5,2,3,2,7,2,8,2,4,2,2,41,41,37,12,11,
-11,16,0,16,0,16,0,36,36,11,12,11,11,16,0,16,0,16,0,36,36,
-16,2,20,15,16,6,253,22,135,11,2,3,11,38,36,11,248,22,89,249,22,
-79,22,186,10,88,163,36,37,45,44,9,223,9,33,9,80,159,36,36,37,80,
-159,36,37,37,80,159,36,38,37,80,159,36,39,37,80,159,36,40,37,20,15,
-16,3,249,22,7,88,163,36,37,45,44,9,223,2,33,10,88,163,36,37,45,
-44,9,223,2,33,11,80,159,36,41,37,80,159,36,42,37,93,29,94,65,113,
-117,111,116,101,68,35,37,107,101,114,110,101,108,11,9,9,9,36,0};
-    EVAL_ONE_SIZED_STR((char *)expr, 501);
+    SHARED_OK static MZCOMPILED_STRING_FAR unsigned char expr[] = {35,126,7,53,46,51,46,49,46,54,84,0,0,0,0,0,0,0,0,0,0,
+0,0,0,0,0,0,0,0,0,0,14,0,0,0,1,0,0,15,0,40,0,
+57,0,75,0,97,0,120,0,140,0,162,0,169,0,176,0,183,0,190,0,197,
+0,0,0,222,1,0,0,74,35,37,112,108,97,99,101,45,115,116,114,117,99,
+116,1,23,115,116,114,117,99,116,58,84,72,45,112,108,97,99,101,45,99,104,
+97,110,110,101,108,76,84,72,45,112,108,97,99,101,45,99,104,97,110,110,101,
+108,77,84,72,45,112,108,97,99,101,45,99,104,97,110,110,101,108,63,1,20,
+84,72,45,112,108,97,99,101,45,99,104,97,110,110,101,108,45,114,101,102,1,
+21,84,72,45,112,108,97,99,101,45,99,104,97,110,110,101,108,45,115,101,116,
+33,79,84,72,45,112,108,97,99,101,45,99,104,97,110,110,101,108,45,105,110,
+1,20,84,72,45,112,108,97,99,101,45,99,104,97,110,110,101,108,45,111,117,
+116,249,80,158,38,39,195,36,249,80,158,38,39,195,36,249,80,158,38,39,195,
+36,249,80,158,38,39,195,37,249,80,158,38,39,195,37,159,36,20,113,159,36,
+16,1,11,16,0,20,26,144,9,2,1,2,1,29,11,11,11,9,9,11,11,
+11,10,45,80,158,36,36,20,113,159,36,16,7,2,2,2,3,2,4,2,5,
+2,6,2,7,2,8,16,0,37,39,36,16,0,36,16,2,2,5,2,6,38,
+11,11,11,16,5,2,3,2,7,2,8,2,4,2,2,16,5,11,11,11,11,
+11,16,5,2,3,2,7,2,8,2,4,2,2,41,41,37,12,11,11,16,0,
+16,0,16,0,36,36,11,12,11,11,16,0,16,0,16,0,36,36,16,3,20,
+15,16,6,253,22,135,11,2,3,11,38,36,11,248,22,89,249,22,79,22,186,
+10,88,163,36,37,45,44,9,223,9,33,9,80,159,36,36,37,80,159,36,37,
+37,80,159,36,38,37,80,159,36,39,37,80,159,36,40,37,20,15,16,2,20,
+27,158,88,163,36,37,45,44,9,223,0,33,10,88,163,36,37,45,44,9,223,
+0,33,11,80,159,36,41,37,20,15,16,2,20,27,158,88,163,36,37,45,44,
+9,223,0,33,12,88,163,36,37,45,44,9,223,0,33,13,80,159,36,42,37,
+93,29,94,65,113,117,111,116,101,68,35,37,107,101,114,110,101,108,11,9,9,
+9,36,0};
+    EVAL_ONE_SIZED_STR((char *)expr, 548);
   }
   {
-    SHARED_OK static MZCOMPILED_STRING_FAR unsigned char expr[] = {35,126,7,53,46,51,46,49,46,53,84,0,0,0,0,0,0,0,0,0,0,
+    SHARED_OK static MZCOMPILED_STRING_FAR unsigned char expr[] = {35,126,7,53,46,51,46,49,46,54,84,0,0,0,0,0,0,0,0,0,0,
 0,0,0,0,0,0,0,0,0,0,89,0,0,0,1,0,0,7,0,18,0,
 45,0,51,0,60,0,67,0,89,0,102,0,128,0,145,0,167,0,175,0,187,
 0,202,0,218,0,236,0,0,1,12,1,28,1,51,1,63,1,94,1,101,1,
@@ -682,7 +685,7 @@
 97,116,104,45,115,116,114,105,110,103,63,23,197,2,28,28,23,195,2,28,248,
 22,64,23,196,2,10,28,248,22,88,23,196,2,28,249,22,129,4,248,22,92,
 23,198,2,37,28,28,248,22,64,248,22,80,23,197,2,10,248,22,150,9,248,
-22,163,17,23,197,2,249,22,4,22,64,248,22,164,17,23,198,2,11,11,11,
+22,164,17,23,197,2,249,22,4,22,64,248,22,165,17,23,198,2,11,11,11,
 10,12,250,22,189,9,2,26,6,71,71,40,111,114,47,99,32,35,102,32,115,
 121,109,98,111,108,63,32,40,99,111,110,115,47,99,32,40,111,114,47,99,32,
 35,102,32,115,121,109,98,111,108,63,41,32,40,110,111,110,45,101,109,112,116,
@@ -750,7 +753,7 @@
 11,80,159,8,32,38,37,22,189,4,11,20,13,159,80,159,8,27,38,37,250,
 80,159,8,30,39,37,249,22,33,11,80,159,8,32,38,37,22,172,5,28,248,
 22,184,14,23,218,2,23,217,1,86,94,23,217,1,247,22,161,15,249,247,22,
-170,5,248,22,163,17,195,23,31,86,94,23,193,1,27,28,23,197,1,28,23,
+170,5,248,22,164,17,195,23,31,86,94,23,193,1,27,28,23,197,1,28,23,
 201,1,27,249,22,5,20,20,95,88,163,36,37,48,8,128,3,9,226,31,26,
 25,22,33,53,23,215,1,23,219,1,23,220,1,27,28,23,205,2,11,193,28,
 192,192,28,193,28,204,28,249,22,131,4,248,22,81,196,248,22,81,23,15,193,
@@ -761,9 +764,9 @@
 28,38,37,250,80,159,8,31,39,37,249,22,33,11,80,159,8,33,38,37,22,
 189,4,23,217,1,20,13,159,80,159,8,28,38,37,250,80,159,8,31,39,37,
 249,22,33,11,80,159,8,33,38,37,22,172,5,28,248,22,184,14,23,219,2,
-23,218,1,86,94,23,218,1,247,22,161,15,249,247,22,170,5,248,22,163,17,
+23,218,1,86,94,23,218,1,247,22,161,15,249,247,22,170,5,248,22,164,17,
 195,23,32,86,94,23,193,1,28,28,248,22,77,23,224,32,0,0,0,2,248,
-22,163,17,23,224,32,0,0,0,2,10,27,28,23,199,2,86,94,23,215,1,
+22,164,17,23,224,32,0,0,0,2,10,27,28,23,199,2,86,94,23,215,1,
 23,214,1,86,94,23,214,1,23,215,1,28,28,248,22,77,23,224,33,0,0,
 0,2,248,22,150,9,248,22,132,15,23,195,2,11,12,20,13,159,80,159,8,
 29,38,37,250,80,159,8,32,39,37,249,22,33,11,80,159,8,34,38,37,22,
@@ -787,13 +790,13 @@
 193,2,86,94,23,194,1,249,22,79,248,22,104,23,196,2,248,2,59,248,22,
 113,23,197,1,248,22,89,194,248,22,89,194,248,22,89,194,248,22,89,194,32,
 61,88,163,36,37,55,11,2,31,222,33,62,28,248,22,87,248,22,81,23,195,
-2,249,22,7,9,248,22,163,17,195,90,159,38,11,89,161,38,36,11,27,248,
-22,164,17,196,28,248,22,87,248,22,81,23,195,2,249,22,7,9,248,22,163,
-17,195,90,159,38,11,89,161,38,36,11,27,248,22,164,17,196,28,248,22,87,
-248,22,81,23,195,2,249,22,7,9,248,22,163,17,195,90,159,38,11,89,161,
-38,36,11,248,2,61,248,22,164,17,196,249,22,7,249,22,79,248,22,163,17,
-199,196,195,249,22,7,249,22,79,248,22,163,17,199,196,195,249,22,7,249,22,
-79,248,22,163,17,199,196,195,27,27,249,22,173,15,2,58,23,197,2,28,23,
+2,249,22,7,9,248,22,164,17,195,90,159,38,11,89,161,38,36,11,27,248,
+22,165,17,196,28,248,22,87,248,22,81,23,195,2,249,22,7,9,248,22,164,
+17,195,90,159,38,11,89,161,38,36,11,27,248,22,165,17,196,28,248,22,87,
+248,22,81,23,195,2,249,22,7,9,248,22,164,17,195,90,159,38,11,89,161,
+38,36,11,248,2,61,248,22,165,17,196,249,22,7,249,22,79,248,22,164,17,
+199,196,195,249,22,7,249,22,79,248,22,164,17,199,196,195,249,22,7,249,22,
+79,248,22,164,17,199,196,195,27,27,249,22,173,15,2,58,23,197,2,28,23,
 193,2,86,94,23,195,1,249,22,79,248,22,104,23,196,2,27,248,22,113,23,
 197,1,27,249,22,173,15,2,58,23,196,2,28,23,193,2,86,94,23,194,1,
 249,22,79,248,22,104,23,196,2,27,248,22,113,23,197,1,27,249,22,173,15,
@@ -801,20 +804,20 @@
 196,2,27,248,22,113,23,197,1,27,249,22,173,15,2,58,23,196,2,28,23,
 193,2,86,94,23,194,1,249,22,79,248,22,104,23,196,2,248,2,59,248,22,
 113,23,197,1,248,22,89,194,248,22,89,194,248,22,89,194,248,22,89,195,28,
-23,195,1,192,28,248,22,87,248,22,81,23,195,2,249,22,7,9,248,22,163,
-17,195,27,248,22,164,17,194,90,159,38,11,89,161,38,36,11,28,248,22,87,
-248,22,81,23,197,2,249,22,7,9,248,22,163,17,197,27,248,22,164,17,196,
+23,195,1,192,28,248,22,87,248,22,81,23,195,2,249,22,7,9,248,22,164,
+17,195,27,248,22,165,17,194,90,159,38,11,89,161,38,36,11,28,248,22,87,
+248,22,81,23,197,2,249,22,7,9,248,22,164,17,197,27,248,22,165,17,196,
 90,159,38,11,89,161,38,36,11,28,248,22,87,248,22,81,23,197,2,249,22,
-7,9,248,22,163,17,197,90,159,38,11,89,161,38,36,11,248,2,61,248,22,
-164,17,198,249,22,7,249,22,79,248,22,163,17,201,196,195,249,22,7,249,22,
-79,248,22,163,17,202,196,195,249,22,7,249,22,79,248,22,163,17,200,196,195,
+7,9,248,22,164,17,197,90,159,38,11,89,161,38,36,11,248,2,61,248,22,
+165,17,198,249,22,7,249,22,79,248,22,164,17,201,196,195,249,22,7,249,22,
+79,248,22,164,17,202,196,195,249,22,7,249,22,79,248,22,164,17,200,196,195,
 28,24,194,2,12,20,13,159,80,159,36,57,37,80,158,36,55,89,161,37,37,
 10,249,22,190,4,21,94,2,32,6,19,19,112,108,97,110,101,116,47,114,101,
 115,111,108,118,101,114,46,114,107,116,1,27,112,108,97,110,101,116,45,109,111,
 100,117,108,101,45,110,97,109,101,45,114,101,115,111,108,118,101,114,12,27,28,
 23,195,2,28,249,22,152,9,23,197,2,80,158,39,52,86,94,23,195,1,80,
 158,37,53,27,248,22,148,5,23,197,2,27,28,248,22,77,23,195,2,248,22,
-163,17,23,195,1,23,194,1,28,248,22,184,14,23,194,2,90,159,39,11,89,
+164,17,23,195,1,23,194,1,28,248,22,184,14,23,194,2,90,159,39,11,89,
 161,39,36,11,248,22,141,15,23,197,1,86,95,20,18,159,11,80,158,42,52,
 199,20,18,159,11,80,158,42,53,192,192,11,11,28,23,193,2,192,86,94,23,
 193,1,27,247,22,172,5,28,192,192,247,22,161,15,90,159,39,11,89,161,39,
@@ -834,7 +837,7 @@
 22,148,5,23,200,2,248,22,147,5,248,22,80,248,22,148,5,23,201,1,23,
 198,1,27,250,22,160,2,80,159,44,41,38,248,22,134,16,23,204,1,11,28,
 23,193,2,27,250,22,160,2,248,22,81,23,198,1,197,11,28,192,250,22,158,
-2,248,22,164,17,199,197,195,12,12,12,251,211,197,198,199,10,32,71,88,163,
+2,248,22,165,17,199,197,195,12,12,12,251,211,197,198,199,10,32,71,88,163,
 36,38,47,11,76,102,108,97,116,116,101,110,45,115,117,98,45,112,97,116,104,
 222,33,74,32,72,88,163,36,40,54,11,2,31,222,33,73,28,248,22,87,23,
 197,2,28,248,22,87,195,192,249,22,79,194,248,22,94,197,28,249,22,154,9,
@@ -843,8 +846,8 @@
 46,46,34,115,32,105,110,32,115,117,98,109,111,100,117,108,101,32,112,97,116,
 104,58,32,126,46,115,250,22,90,2,34,28,249,22,154,9,23,201,2,2,36,
 198,28,248,22,184,14,199,198,249,22,89,28,248,22,64,201,2,4,2,37,200,
-199,251,2,72,196,197,248,22,81,199,248,22,164,17,200,251,2,72,196,197,249,
-22,79,248,22,163,17,202,200,248,22,164,17,200,251,2,72,196,197,9,197,27,
+199,251,2,72,196,197,248,22,81,199,248,22,165,17,200,251,2,72,196,197,249,
+22,79,248,22,164,17,202,200,248,22,165,17,200,251,2,72,196,197,9,197,27,
 249,22,165,7,6,31,31,115,116,97,110,100,97,114,100,45,109,111,100,117,108,
 101,45,110,97,109,101,45,114,101,115,111,108,118,101,114,58,32,196,28,193,250,
 22,187,9,11,195,196,248,22,185,9,193,28,249,22,148,7,194,2,36,2,28,
@@ -856,7 +859,7 @@
 11,2,31,222,33,81,28,248,22,87,23,194,2,9,250,22,90,6,4,4,10,
 32,32,32,248,22,188,14,248,22,105,23,198,2,248,2,80,248,22,81,23,198,
 1,28,249,22,154,9,248,22,81,23,200,2,23,197,1,28,249,22,152,9,248,
-22,163,17,23,200,1,23,196,1,251,22,185,9,2,22,6,41,41,99,121,99,
+22,164,17,23,200,1,23,196,1,251,22,185,9,2,22,6,41,41,99,121,99,
 108,101,32,105,110,32,108,111,97,100,105,110,103,10,32,32,97,116,32,112,97,
 116,104,58,32,126,97,10,32,32,112,97,116,104,115,58,126,97,23,200,1,249,
 22,1,22,165,7,248,2,80,248,22,94,23,201,1,12,12,247,192,20,13,159,
@@ -868,47 +871,47 @@
 28,248,22,156,5,23,196,2,12,28,23,197,2,250,22,187,9,11,6,15,15,
 98,97,100,32,109,111,100,117,108,101,32,112,97,116,104,23,200,2,250,22,189,
 9,2,22,2,33,23,198,2,28,28,248,22,77,23,196,2,249,22,152,9,248,
-22,163,17,23,198,2,2,4,11,248,22,147,5,248,22,104,196,28,28,248,22,
-77,23,196,2,28,249,22,152,9,248,22,163,17,23,198,2,2,34,28,248,22,
+22,164,17,23,198,2,2,4,11,248,22,147,5,248,22,104,196,28,28,248,22,
+77,23,196,2,28,249,22,152,9,248,22,164,17,23,198,2,2,34,28,248,22,
 77,248,22,104,23,197,2,249,22,152,9,248,22,108,23,198,2,2,4,11,11,
 11,86,97,23,198,1,23,197,1,23,196,1,23,193,1,248,22,147,5,249,2,
 71,248,22,121,23,199,2,248,22,106,23,199,1,28,28,248,22,77,23,196,2,
-28,249,22,152,9,248,22,163,17,23,198,2,2,34,28,28,249,22,154,9,248,
+28,249,22,152,9,248,22,164,17,23,198,2,2,34,28,28,249,22,154,9,248,
 22,104,23,198,2,2,36,10,249,22,154,9,248,22,104,23,198,2,2,35,28,
 23,196,2,27,248,22,148,5,23,198,2,28,248,22,64,193,10,28,248,22,77,
-193,248,22,64,248,22,163,17,194,11,11,11,11,11,86,96,23,198,1,23,197,
+193,248,22,64,248,22,164,17,194,11,11,11,11,11,86,96,23,198,1,23,197,
 1,23,193,1,27,248,22,148,5,23,198,1,248,22,147,5,249,2,71,28,248,
-22,77,23,197,2,248,22,163,17,23,197,2,23,196,2,27,28,249,22,154,9,
-248,22,104,23,203,2,2,35,248,22,164,17,200,248,22,106,200,28,248,22,77,
-23,198,2,249,22,93,248,22,164,17,199,194,192,28,28,248,22,77,23,196,2,
-249,22,152,9,248,22,163,17,23,198,2,2,38,11,86,94,248,80,159,38,8,
+22,77,23,197,2,248,22,164,17,23,197,2,23,196,2,27,28,249,22,154,9,
+248,22,104,23,203,2,2,35,248,22,165,17,200,248,22,106,200,28,248,22,77,
+23,198,2,249,22,93,248,22,165,17,199,194,192,28,28,248,22,77,23,196,2,
+249,22,152,9,248,22,164,17,23,198,2,2,38,11,86,94,248,80,159,38,8,
 28,39,193,253,213,200,201,202,203,11,80,158,43,55,28,28,248,22,77,23,196,
-2,28,249,22,152,9,248,22,163,17,23,198,2,2,34,28,248,22,77,248,22,
+2,28,249,22,152,9,248,22,164,17,23,198,2,2,34,28,248,22,77,248,22,
 104,23,197,2,249,22,152,9,248,22,108,23,198,2,2,38,11,11,11,86,94,
 248,80,159,38,8,28,39,193,253,213,248,22,104,201,201,202,203,248,22,106,201,
 80,158,43,55,86,94,23,193,1,27,88,163,8,36,37,47,11,79,115,104,111,
 119,45,99,111,108,108,101,99,116,105,111,110,45,101,114,114,223,5,33,75,27,
-28,248,22,77,23,198,2,28,249,22,152,9,2,34,248,22,163,17,23,200,2,
+28,248,22,77,23,198,2,28,249,22,152,9,2,34,248,22,164,17,23,200,2,
 27,248,22,104,23,199,2,28,28,249,22,154,9,23,195,2,2,36,10,249,22,
 154,9,23,195,2,2,35,86,94,23,193,1,28,23,199,2,27,248,22,148,5,
-23,201,2,28,248,22,77,193,248,22,163,17,193,192,250,22,185,9,2,22,6,
+23,201,2,28,248,22,77,193,248,22,164,17,193,192,250,22,185,9,2,22,6,
 45,45,110,111,32,98,97,115,101,32,112,97,116,104,32,102,111,114,32,114,101,
 108,97,116,105,118,101,32,115,117,98,109,111,100,117,108,101,32,112,97,116,104,
 58,32,126,46,115,23,201,2,192,23,197,2,23,197,2,27,28,248,22,77,23,
-199,2,28,249,22,152,9,2,34,248,22,163,17,23,201,2,27,28,28,28,249,
+199,2,28,249,22,152,9,2,34,248,22,164,17,23,201,2,27,28,28,28,249,
 22,154,9,248,22,104,23,202,2,2,36,10,249,22,154,9,248,22,104,23,202,
 2,2,35,23,200,2,11,27,248,22,148,5,23,202,2,27,28,249,22,154,9,
-248,22,104,23,204,2,2,35,248,22,164,17,23,202,1,248,22,106,23,202,1,
-28,248,22,77,23,195,2,249,2,71,248,22,163,17,23,197,2,249,22,93,248,
-22,164,17,23,199,1,23,197,1,249,2,71,23,196,1,23,195,1,249,2,71,
-2,36,28,249,22,154,9,248,22,104,23,204,2,2,35,248,22,164,17,23,202,
-1,248,22,106,23,202,1,28,248,22,77,193,248,22,164,17,193,11,11,11,27,
+248,22,104,23,204,2,2,35,248,22,165,17,23,202,1,248,22,106,23,202,1,
+28,248,22,77,23,195,2,249,2,71,248,22,164,17,23,197,2,249,22,93,248,
+22,165,17,23,199,1,23,197,1,249,2,71,23,196,1,23,195,1,249,2,71,
+2,36,28,249,22,154,9,248,22,104,23,204,2,2,35,248,22,165,17,23,202,
+1,248,22,106,23,202,1,28,248,22,77,193,248,22,165,17,193,11,11,11,27,
 28,248,22,64,23,196,2,27,248,80,159,43,48,39,249,22,79,23,199,2,247,
 22,162,15,28,23,193,2,192,86,94,23,193,1,90,159,38,11,89,161,38,36,
 11,249,80,159,46,54,39,248,22,70,23,201,2,11,27,28,248,22,87,23,195,
 2,2,39,249,22,165,7,23,197,2,2,40,251,80,159,49,59,39,23,204,1,
 28,248,22,87,23,199,2,23,199,1,86,94,23,199,1,248,22,80,23,199,2,
-28,248,22,87,23,199,2,86,94,23,198,1,9,248,22,164,17,23,199,1,23,
+28,248,22,87,23,199,2,86,94,23,198,1,9,248,22,165,17,23,199,1,23,
 197,1,28,248,22,142,7,23,196,2,86,94,23,196,1,27,248,80,159,43,8,
 29,39,23,202,2,27,248,80,159,44,48,39,249,22,79,23,200,2,23,197,2,
 28,23,193,2,192,86,94,23,193,1,90,159,38,11,89,161,38,36,11,249,80,
@@ -928,7 +931,7 @@
 249,22,1,22,93,249,22,2,80,159,53,8,31,39,248,22,106,23,208,2,23,
 197,1,28,248,22,87,23,196,2,86,94,23,195,1,248,22,89,23,197,1,86,
 94,23,196,1,23,195,1,251,80,159,51,59,39,23,206,1,248,22,80,23,198,
-2,248,22,164,17,23,198,1,23,198,1,28,249,22,152,9,248,22,163,17,23,
+2,248,22,165,17,23,198,1,23,198,1,28,249,22,152,9,248,22,164,17,23,
 198,2,2,37,248,80,159,42,8,30,39,248,22,147,15,249,22,145,15,248,22,
 149,15,248,22,104,23,201,2,248,80,159,46,8,29,39,23,205,2,12,86,94,
 28,28,248,22,184,14,23,194,2,10,248,22,167,8,23,194,2,86,94,23,201,
@@ -956,7 +959,7 @@
 20,20,96,88,163,36,36,56,8,240,12,64,0,0,9,230,19,15,13,12,8,
 7,5,2,33,84,23,195,1,23,198,1,23,208,1,12,28,28,248,22,167,8,
 23,204,1,11,28,248,22,142,7,23,206,2,10,28,248,22,64,23,206,2,10,
-28,248,22,77,23,206,2,249,22,152,9,248,22,163,17,23,208,2,2,32,11,
+28,248,22,77,23,206,2,249,22,152,9,248,22,164,17,23,208,2,2,32,11,
 249,80,159,53,49,39,28,248,22,142,7,23,208,2,249,22,79,23,209,1,248,
 80,159,56,8,29,39,23,215,1,86,94,23,212,1,249,22,79,23,209,1,247,
 22,162,15,252,22,169,8,23,209,1,23,208,1,23,206,1,23,204,1,23,203,
@@ -1017,7 +1020,7 @@
     EVAL_ONE_SIZED_STR((char *)expr, 8518);
   }
   {
-    SHARED_OK static MZCOMPILED_STRING_FAR unsigned char expr[] = {35,126,7,53,46,51,46,49,46,53,84,0,0,0,0,0,0,0,0,0,0,
+    SHARED_OK static MZCOMPILED_STRING_FAR unsigned char expr[] = {35,126,7,53,46,51,46,49,46,54,84,0,0,0,0,0,0,0,0,0,0,
 0,0,0,0,0,0,0,0,0,0,11,0,0,0,1,0,0,10,0,16,0,
 29,0,44,0,58,0,78,0,90,0,104,0,118,0,170,0,0,0,98,1,0,
 0,69,35,37,98,117,105,108,116,105,110,65,113,117,111,116,101,29,94,2,2,
diff --git a/src/racket/src/jit.h b/src/racket/src/jit.h
index 9213036b28..8299770a8e 100644
--- a/src/racket/src/jit.h
+++ b/src/racket/src/jit.h
@@ -1228,7 +1228,7 @@ int scheme_generate_inlined_nary(mz_jit_state *jitter, Scheme_App_Rec *app, int
                                  int dest);
 int scheme_generate_inlined_test(mz_jit_state *jitter, Scheme_Object *obj, int branch_short, 
                                  Branch_Info *for_branch, int need_sync);
-int scheme_generate_cons_alloc(mz_jit_state *jitter, int rev, int inline_retry, int dest);
+int scheme_generate_cons_alloc(mz_jit_state *jitter, int rev, int inline_retry, int known_list, int dest);
 int scheme_generate_struct_alloc(mz_jit_state *jitter, int num_args, 
                                  int inline_slow, int pop_and_jump,
                                  int is_tail, int multi_ok, int dest);
@@ -1238,7 +1238,7 @@ int scheme_generate_struct_alloc(mz_jit_state *jitter, int num_args,
 /**********************************************************************/
 
 #ifdef CAN_INLINE_ALLOC
-int scheme_inline_alloc(mz_jit_state *jitter, int amt, Scheme_Type ty, int immut,
+int scheme_inline_alloc(mz_jit_state *jitter, int amt, Scheme_Type ty, int flags,
 			int keep_r0_r1, int keep_fpr1, int inline_retry);
 int scheme_generate_alloc_retry(mz_jit_state *jitter, int i);
 #else
diff --git a/src/racket/src/jitcommon.c b/src/racket/src/jitcommon.c
index 9ad26f42be..17ee2455a9 100644
--- a/src/racket/src/jitcommon.c
+++ b/src/racket/src/jitcommon.c
@@ -2168,7 +2168,7 @@ static int common5(mz_jit_state *jitter, void *_data)
     jit_ldxr_p(JIT_R1, JIT_RUNSTACK, JIT_R2);
     mz_set_local_p(JIT_R2, JIT_LOCAL3);
 
-    scheme_generate_cons_alloc(jitter, 1, 1, JIT_R0);
+    scheme_generate_cons_alloc(jitter, 1, 1, !i, JIT_R0);
     CHECK_LIMIT();
 
     mz_get_local_p(JIT_R2, JIT_LOCAL3);
diff --git a/src/racket/src/jitinline.c b/src/racket/src/jitinline.c
index 3d46e6c331..70afb2cf5d 100644
--- a/src/racket/src/jitinline.c
+++ b/src/racket/src/jitinline.c
@@ -1053,7 +1053,7 @@ int scheme_generate_inlined_unary(mz_jit_state *jitter, Scheme_App2_Rec *app, in
     scheme_generate_arith(jitter, rator, app->rand, NULL, 1, 0, CMP_ODDP, 0, for_branch, branch_short, 0, 0, NULL, dest);
     return 1;
   } else if (IS_NAMED_PRIM(rator, "list?")) {
-    GC_CAN_IGNORE jit_insn *ref0, *ref1, *ref3, *ref4;
+    GC_CAN_IGNORE jit_insn *ref0, *ref1, *ref3, *ref4, *ref6;
 
     mz_runstack_skipped(jitter, 1);
     
@@ -1077,11 +1077,16 @@ int scheme_generate_inlined_unary(mz_jit_state *jitter, Scheme_App2_Rec *app, in
     ref4 = jit_bnei_p(jit_forward(), JIT_R1, scheme_pair_type);
     CHECK_LIMIT();
 
+    /* We have a pair. Optimistically check for PAIR_IS_LIST: */
+    jit_ldxi_s(JIT_R2, JIT_R0, &MZ_OPT_HASH_KEY(&((Scheme_Stx *)0x0)->iso));
+    ref6 = jit_bmsi_ul(jit_forward(), JIT_R2, PAIR_IS_LIST);
+
     if (for_branch) {
       ref0 = jit_patchable_movi_p(JIT_V1, jit_forward());
       (void)jit_calli(sjc.list_p_branch_code);
 
       mz_patch_branch(ref3);
+      mz_patch_branch(ref6);
 
       scheme_add_branch_false_movi(for_branch, ref0);
       scheme_add_branch_false(for_branch, ref1);
@@ -1100,6 +1105,7 @@ int scheme_generate_inlined_unary(mz_jit_state *jitter, Scheme_App2_Rec *app, in
       ref1 = jit_jmpi(jit_forward());
       
       mz_patch_branch(ref3);
+      mz_patch_branch(ref6);
       (void)jit_movi_p(dest, scheme_true);
 
       mz_patch_ucbranch(ref5);
@@ -1721,7 +1727,7 @@ int scheme_generate_inlined_unary(mz_jit_state *jitter, Scheme_App2_Rec *app, in
       mz_rs_sync();
       mz_runstack_unskipped(jitter, 1);
       (void)jit_movi_p(JIT_R1, &scheme_null);
-      return scheme_generate_cons_alloc(jitter, 0, 0, dest);
+      return scheme_generate_cons_alloc(jitter, 0, 0, 1, dest);
     } else if (IS_NAMED_PRIM(rator, "box")) {
       mz_runstack_skipped(jitter, 1);
       scheme_generate_non_tail(app->rand, jitter, 0, 1, 0);
@@ -3023,14 +3029,28 @@ int scheme_generate_inlined_binary(mz_jit_state *jitter, Scheme_App3_Rec *app, i
       return 1;
     } else if (IS_NAMED_PRIM(rator, "cons")
                || IS_NAMED_PRIM(rator, "list*")) {
-      int dir;
+      int dir, known_list;
       LOG_IT(("inlined cons\n"));
 
       dir = generate_two_args(app->rand1, app->rand2, jitter, 0, 2);
       CHECK_LIMIT();
       mz_rs_sync();
+      
+      if (scheme_is_list(app->rand2))
+        known_list = 1;
+      else
+        known_list = 2;
 
-      return scheme_generate_cons_alloc(jitter, dir == -1, 0, dest);
+      return scheme_generate_cons_alloc(jitter, dir == -1, 0, known_list, dest);
+    } else if (IS_NAMED_PRIM(rator, "unsafe-cons-list")) {
+      int dir;
+      LOG_IT(("inlined unsafe-cons-list\n"));
+
+      dir = generate_two_args(app->rand1, app->rand2, jitter, 0, 2);
+      CHECK_LIMIT();
+      mz_rs_sync();
+
+      return scheme_generate_cons_alloc(jitter, dir == -1, 0, 1, dest);
     } else if (IS_NAMED_PRIM(rator, "mcons")) {
       LOG_IT(("inlined mcons\n"));
 
@@ -3074,7 +3094,7 @@ int scheme_generate_inlined_binary(mz_jit_state *jitter, Scheme_App3_Rec *app, i
       CHECK_LIMIT();
       mz_rs_sync();
 
-      scheme_generate_cons_alloc(jitter, 1, 0, JIT_R0);
+      scheme_generate_cons_alloc(jitter, 1, 0, 1, JIT_R0);
       CHECK_LIMIT();
 
       jit_ldr_p(JIT_R1, JIT_RUNSTACK);
@@ -3082,7 +3102,7 @@ int scheme_generate_inlined_binary(mz_jit_state *jitter, Scheme_App3_Rec *app, i
       mz_runstack_popped(jitter, 1);
       CHECK_LIMIT();
       
-      return scheme_generate_cons_alloc(jitter, 1, 0, dest);
+      return scheme_generate_cons_alloc(jitter, 1, 0, 1, dest);
     } else if (IS_NAMED_PRIM(rator, "vector-immutable")
                || IS_NAMED_PRIM(rator, "vector")) {
       return generate_vector_alloc(jitter, rator, NULL, NULL, app, dest);
@@ -3780,28 +3800,50 @@ int scheme_generate_inlined_nary(mz_jit_state *jitter, Scheme_App_Rec *app, int
       CHECK_LIMIT();
       mz_rs_sync();
 
+      if (c <= 4) {
+        /* fully inline a small list */
+        int i, c2 = c, known_list;
+        if (star) {
+          c2--;
+          mz_rs_ldxi(JIT_R1, c2);
+          known_list = scheme_is_list(app->args[c2]);
+        } else {
+          known_list = 1;
+          if (c)
+            (void)jit_movi_p(JIT_R1, scheme_null);
+          else
+            (void)jit_movi_p(dest, scheme_null);
+        }
+
+        for (i = c2; i--; ) {
+          mz_rs_ldxi(JIT_R0, i);
+          scheme_generate_cons_alloc(jitter, 0, 0, known_list, (i > 0) ? JIT_R1 : dest);
+          CHECK_LIMIT();
+        }
+      } else {
 #ifdef CAN_INLINE_ALLOC
-      jit_movi_l(JIT_R2, c);
-      if (star)
-        (void)jit_calli(sjc.make_list_star_code);
-      else
-        (void)jit_calli(sjc.make_list_code);
-      jit_movr_p(dest, JIT_R0);
-#else
-      JIT_UPDATE_THREAD_RSPTR_IF_NEEDED();
-      jit_movi_l(JIT_R0, c);
-      mz_prepare(2);
-      jit_pusharg_l(JIT_R0);
-      jit_pusharg_p(JIT_RUNSTACK);
-      {
-        GC_CAN_IGNORE jit_insn *refr;
+        jit_movi_l(JIT_R2, c);
         if (star)
-          (void)mz_finish_lwe(ts_scheme_jit_make_list_star, refr);
+          (void)jit_calli(sjc.make_list_star_code);
         else
-          (void)mz_finish_lwe(ts_scheme_jit_make_list, refr);
-      }
-      jit_retval(dest);
+          (void)jit_calli(sjc.make_list_code);
+        jit_movr_p(dest, JIT_R0);
+#else
+        JIT_UPDATE_THREAD_RSPTR_IF_NEEDED();
+        jit_movi_l(JIT_R0, c);
+        mz_prepare(2);
+        jit_pusharg_l(JIT_R0);
+        jit_pusharg_p(JIT_RUNSTACK);
+        {
+          GC_CAN_IGNORE jit_insn *refr;
+          if (star)
+            (void)mz_finish_lwe(ts_scheme_jit_make_list_star, refr);
+          else
+            (void)mz_finish_lwe(ts_scheme_jit_make_list, refr);
+        }
+        jit_retval(dest);
 #endif
+      }
 
       if (c) {
         mz_rs_inc(c); /* no sync */
@@ -3877,12 +3919,13 @@ int scheme_generate_inlined_nary(mz_jit_state *jitter, Scheme_App_Rec *app, int
   return 0;
 }
 
-int scheme_generate_cons_alloc(mz_jit_state *jitter, int rev, int inline_retry, int dest)
+int scheme_generate_cons_alloc(mz_jit_state *jitter, int rev, int inline_retry, int known_list, int dest)
 /* Args must be in R0 (car) and R1 (cdr); uses R2 and V1 as temporaries */
 {
 #ifdef CAN_INLINE_ALLOC
   /* Inlined alloc */
-  scheme_inline_alloc(jitter, sizeof(Scheme_Simple_Object), scheme_pair_type, 0, 1, 0, inline_retry);
+  scheme_inline_alloc(jitter, sizeof(Scheme_Simple_Object), scheme_pair_type, 0, 1, 
+                      known_list ? PAIR_IS_LIST : 0, inline_retry);
   CHECK_LIMIT();
   
   if (rev) {
diff --git a/src/racket/src/list.c b/src/racket/src/list.c
index 238998cf37..b02e59c0f0 100644
--- a/src/racket/src/list.c
+++ b/src/racket/src/list.c
@@ -37,6 +37,7 @@ READ_ONLY Scheme_Object *scheme_list_star_proc;
 READ_ONLY Scheme_Object *scheme_box_proc;
 READ_ONLY Scheme_Object *scheme_box_p_proc;
 READ_ONLY Scheme_Object *scheme_hash_ref_proc;
+READ_ONLY Scheme_Object *scheme_unsafe_cons_list_proc;
 READ_ONLY Scheme_Object *scheme_unsafe_car_proc;
 READ_ONLY Scheme_Object *scheme_unsafe_cdr_proc;
 READ_ONLY Scheme_Object *scheme_unsafe_mcar_proc;
@@ -155,6 +156,7 @@ static Scheme_Object *make_hasheq_placeholder(int argc, Scheme_Object *argv[]);
 static Scheme_Object *make_hasheqv_placeholder(int argc, Scheme_Object *argv[]);
 static Scheme_Object *table_placeholder_p(int argc, Scheme_Object *argv[]);
 
+static Scheme_Object *unsafe_cons_list (int argc, Scheme_Object *argv[]);
 static Scheme_Object *unsafe_car (int argc, Scheme_Object *argv[]);
 static Scheme_Object *unsafe_cdr (int argc, Scheme_Object *argv[]);
 static Scheme_Object *unsafe_list_ref (int argc, Scheme_Object *argv[]);
@@ -752,6 +754,13 @@ scheme_init_unsafe_list (Scheme_Env *env)
   
   scheme_null->type = scheme_null_type;
 
+  REGISTER_SO(scheme_unsafe_cons_list_proc);
+  p = scheme_make_immed_prim(unsafe_cons_list, "unsafe-cons-list", 2, 2);
+  SCHEME_PRIM_PROC_FLAGS(p) |= (SCHEME_PRIM_IS_BINARY_INLINED
+                                | SCHEME_PRIM_IS_OMITABLE);
+  scheme_add_global_constant ("unsafe-cons-list", p, env);
+  scheme_unsafe_cons_list_proc = p;
+
   REGISTER_SO(scheme_unsafe_car_proc);
   p = scheme_make_folding_prim(unsafe_car, "unsafe-car", 1, 1, 1);
   SCHEME_PRIM_PROC_FLAGS(p) |= (SCHEME_PRIM_IS_UNARY_INLINED
@@ -842,6 +851,14 @@ Scheme_Object *scheme_make_pair(Scheme_Object *car, Scheme_Object *cdr)
 #endif
 }
 
+Scheme_Object *scheme_make_list_pair(Scheme_Object *car, Scheme_Object *cdr)
+{
+  GC_CAN_IGNORE Scheme_Object *r;
+  r = scheme_make_pair(car, cdr);
+  SCHEME_PAIR_FLAGS(r) |= PAIR_IS_LIST;
+  return r;
+}
+
 Scheme_Object *scheme_make_mutable_pair(Scheme_Object *car, Scheme_Object *cdr)
 {
   Scheme_Object *cons;
@@ -877,6 +894,7 @@ Scheme_Object *scheme_make_raw_pair(Scheme_Object *car, Scheme_Object *cdr)
 }
 
 # define cons(car, cdr) scheme_make_pair(car, cdr)
+# define lcons(car, cdr) scheme_make_list_pair(car, cdr)
 
 Scheme_Object *scheme_build_list(int size, Scheme_Object **argv)
 {
@@ -884,7 +902,7 @@ Scheme_Object *scheme_build_list(int size, Scheme_Object **argv)
   int i;
 
   for (i = size; i--; ) {
-    pair = cons(argv[i], pair);
+    pair = lcons(argv[i], pair);
   }
 
   return pair;
@@ -900,12 +918,12 @@ Scheme_Object *scheme_build_list_offset(int size, Scheme_Object **argv, int delt
     /* clearing mode: */
     size = -size;
     for (i = size; i-- > delta; ) {
-      pair = cons(argv[i], pair);
+      pair = lcons(argv[i], pair);
       argv[i] = NULL;
     }
   } else {
     for (i = size; i-- > delta; ) {
-      pair = cons(argv[i], pair);
+      pair = lcons(argv[i], pair);
     }
   }
 
@@ -918,7 +936,7 @@ Scheme_Object *scheme_alloc_list(int size)
   int i;
 
   for (i = size; i--; ) {
-    pair = cons(scheme_false, pair);
+    pair = lcons(scheme_false, pair);
   }
 
   return pair;
@@ -968,7 +986,7 @@ scheme_named_map_1(char *name, Scheme_Object *(*fun)(Scheme_Object*, Scheme_Obje
     Scheme_Object *v;
     v = SCHEME_STX_CAR(lst);
     v = fun(v, form);
-    pr = cons(v, scheme_null);
+    pr = lcons(v, scheme_null);
     if (last)
       SCHEME_CDR(last) = pr;
     else
@@ -1168,10 +1186,18 @@ int scheme_is_list(Scheme_Object *obj1)
   }
 
   /* Propagate info further up the chain. */
-  /* We could have a race with JIT-generated code, but the worst
-     should be that we lose a flag setting (dangerous in principle,
-     but not in practice). */
+#ifdef MZ_USE_FUTURES
+  {
+    short orig_flags = flags & (~PAIR_FLAG_MASK);
+    while (!mzrt_cas16(&SCHEME_PAIR_FLAGS(obj2), orig_flags, flags)) {
+      orig_flags = SCHEME_PAIR_FLAGS(obj2);
+      flags = orig_flags | (flags & PAIR_FLAG_MASK);
+    }
+  }
+#else
+  /* no fuel check, so flags could not have changed */
   SCHEME_PAIR_FLAGS(obj2) |= (flags & PAIR_FLAG_MASK);
+#endif
 
   return (flags & PAIR_IS_LIST);
 }
@@ -1187,7 +1213,7 @@ list_p_prim (int argc, Scheme_Object *argv[])
 #define NORMAL_LIST_INIT() l = scheme_null
 #define STAR_LIST_INIT() --argc; l = argv[argc]
 
-#define LIST_BODY(INIT)                          \
+#define LIST_BODY(INIT, cons)                    \
   int i;                                         \
   GC_CAN_IGNORE Scheme_Object *l;                \
   INIT;                                          \
@@ -1199,13 +1225,13 @@ list_p_prim (int argc, Scheme_Object *argv[])
 static Scheme_Object *
 list_prim (int argc, Scheme_Object *argv[])
 {
-  LIST_BODY(NORMAL_LIST_INIT());
+  LIST_BODY(NORMAL_LIST_INIT(), lcons);
 }
 
 static Scheme_Object *
 list_star_prim (int argc, Scheme_Object *argv[])
 {
-  LIST_BODY(STAR_LIST_INIT());
+  LIST_BODY(STAR_LIST_INIT(), cons);
 }
 
 static Scheme_Object *
@@ -1313,7 +1339,7 @@ reverse_prim (int argc, Scheme_Object *argv[])
   while (!SCHEME_NULLP (lst)) {
     if (!SCHEME_PAIRP(lst))
       scheme_wrong_contract("reverse", "list?", 0, argc, argv);
-    last = cons(SCHEME_CAR (lst), last);
+    last = lcons(SCHEME_CAR (lst), last);
     lst = SCHEME_CDR (lst);
 
     SCHEME_USE_FUEL(1);
@@ -2498,7 +2524,7 @@ static Scheme_Object *do_map_hash_table(int argc,
           p[1] = v;
           if (keep) {
             v = _scheme_apply(f, 2, p);
-            v = cons(v, scheme_null);
+            v = lcons(v, scheme_null);
             if (last)
               SCHEME_CDR(last) = v;
             else
@@ -2530,7 +2556,7 @@ static Scheme_Object *do_map_hash_table(int argc,
           p[1] = v;
           if (keep) {
             v = _scheme_apply(f, 2, p);
-            v = cons(v, scheme_null);
+            v = lcons(v, scheme_null);
             if (last)
               SCHEME_CDR(last) = v;
             else
@@ -2562,7 +2588,7 @@ static Scheme_Object *do_map_hash_table(int argc,
         p[1] = iv;
         if (keep) {
           v = _scheme_apply(f, 2, p);
-          v = cons(v, scheme_null);
+          v = lcons(v, scheme_null);
           if (last)
             SCHEME_CDR(last) = v;
           else
@@ -3559,6 +3585,12 @@ void scheme_init_ephemerons(void)
 /*                        unsafe                            */
 /************************************************************/
 
+static Scheme_Object *unsafe_cons_list(int argc, Scheme_Object *argv[])
+{
+  return lcons(argv[0], argv[1]);
+}
+
+
 static Scheme_Object *unsafe_car (int argc, Scheme_Object *argv[])
 {
   if (scheme_current_thread->constant_folding) return scheme_checked_car(argc, argv);
diff --git a/src/racket/src/optimize.c b/src/racket/src/optimize.c
index 4faced20d1..8355748ee3 100644
--- a/src/racket/src/optimize.c
+++ b/src/racket/src/optimize.c
@@ -945,6 +945,7 @@ static int is_movable_prim(Scheme_Object *rator, int n, int cross_lambda)
          return values that contain all arguments: */
       && (SAME_OBJ(scheme_list_proc, rator)
           || (SAME_OBJ(scheme_cons_proc, rator) && (n == 2))
+          || (SAME_OBJ(scheme_unsafe_cons_list_proc, rator) && (n == 2))
           || SAME_OBJ(scheme_list_star_proc, rator)
           || SAME_OBJ(scheme_vector_proc, rator)
           || SAME_OBJ(scheme_vector_immutable_proc, rator)
@@ -2410,6 +2411,7 @@ static Scheme_Object *finish_optimize_application2(Scheme_App2_Rec *app, Optimiz
       Scheme_App3_Rec *app3 = (Scheme_App3_Rec *)rand;
       if (IS_NAMED_PRIM(app->rator, "car")) {
         if (SAME_OBJ(scheme_cons_proc, app3->rator)
+            || SAME_OBJ(scheme_unsafe_cons_list_proc, app3->rator)
             || SAME_OBJ(scheme_list_proc, app3->rator)
             || SAME_OBJ(scheme_list_star_proc, app3->rator)) {
           /* (car ({cons|list|list*} X Y)) */
@@ -2421,7 +2423,8 @@ static Scheme_Object *finish_optimize_application2(Scheme_App2_Rec *app, Optimiz
         }
       } else if (IS_NAMED_PRIM(app->rator, "cdr")) {
         /* (cdr (cons X Y)) */
-        if (SAME_OBJ(scheme_cons_proc, app3->rator)) {
+        if (SAME_OBJ(scheme_cons_proc, app3->rator)
+            || SAME_OBJ(scheme_unsafe_cons_list_proc, app3->rator)) {
           if ((scheme_omittable_expr(app3->rand2, 1, 5, 0, info, NULL, -1, 0)
                || single_valued_noncm_expression(app3->rand2, 5))
               && scheme_omittable_expr(app3->rand1, 1, 5, 0, info, NULL, -1, 0)) {
diff --git a/src/racket/src/schemef.h b/src/racket/src/schemef.h
index beddc17b97..6773dd5f8d 100644
--- a/src/racket/src/schemef.h
+++ b/src/racket/src/schemef.h
@@ -568,6 +568,7 @@ MZ_EXTERN void scheme_prim_is_method(Scheme_Object *o);
 
 MZ_EXTERN Scheme_Object *scheme_make_pair(Scheme_Object *car, Scheme_Object *cdr);
 MZ_EXTERN Scheme_Object *scheme_make_mutable_pair(Scheme_Object *car, Scheme_Object *cdr);
+MZ_EXTERN Scheme_Object *scheme_make_list_pair(Scheme_Object *car, Scheme_Object *cdr);
 
 MZ_EXTERN Scheme_Object *scheme_make_raw_pair(Scheme_Object *, Scheme_Object *);
 
diff --git a/src/racket/src/schemex.h b/src/racket/src/schemex.h
index 10e32c36ea..071fd9a07d 100644
--- a/src/racket/src/schemex.h
+++ b/src/racket/src/schemex.h
@@ -454,6 +454,7 @@ Scheme_Object *(*scheme_make_closed_prim_w_everything)(Scheme_Closed_Prim *fun,
 void (*scheme_prim_is_method)(Scheme_Object *o);
 Scheme_Object *(*scheme_make_pair)(Scheme_Object *car, Scheme_Object *cdr);
 Scheme_Object *(*scheme_make_mutable_pair)(Scheme_Object *car, Scheme_Object *cdr);
+Scheme_Object *(*scheme_make_list_pair)(Scheme_Object *car, Scheme_Object *cdr);
 Scheme_Object *(*scheme_make_raw_pair)(Scheme_Object *, Scheme_Object *);
 Scheme_Object *(*scheme_make_byte_string)(const char *chars);
 Scheme_Object *(*scheme_make_sized_byte_string)(char *chars, intptr_t len, int copy);
diff --git a/src/racket/src/schemex.inc b/src/racket/src/schemex.inc
index 3e3e6f2cec..715e75e96c 100644
--- a/src/racket/src/schemex.inc
+++ b/src/racket/src/schemex.inc
@@ -319,6 +319,7 @@
   scheme_extension_table->scheme_prim_is_method = scheme_prim_is_method;
   scheme_extension_table->scheme_make_pair = scheme_make_pair;
   scheme_extension_table->scheme_make_mutable_pair = scheme_make_mutable_pair;
+  scheme_extension_table->scheme_make_list_pair = scheme_make_list_pair;
   scheme_extension_table->scheme_make_raw_pair = scheme_make_raw_pair;
   scheme_extension_table->scheme_make_byte_string = scheme_make_byte_string;
   scheme_extension_table->scheme_make_sized_byte_string = scheme_make_sized_byte_string;
diff --git a/src/racket/src/schemexm.h b/src/racket/src/schemexm.h
index a3ef033eb5..5bdc858f34 100644
--- a/src/racket/src/schemexm.h
+++ b/src/racket/src/schemexm.h
@@ -319,6 +319,7 @@
 #define scheme_prim_is_method (scheme_extension_table->scheme_prim_is_method)
 #define scheme_make_pair (scheme_extension_table->scheme_make_pair)
 #define scheme_make_mutable_pair (scheme_extension_table->scheme_make_mutable_pair)
+#define scheme_make_list_pair (scheme_extension_table->scheme_make_list_pair)
 #define scheme_make_raw_pair (scheme_extension_table->scheme_make_raw_pair)
 #define scheme_make_byte_string (scheme_extension_table->scheme_make_byte_string)
 #define scheme_make_sized_byte_string (scheme_extension_table->scheme_make_sized_byte_string)
diff --git a/src/racket/src/schminc.h b/src/racket/src/schminc.h
index ff770ac4ed..5c130612c0 100644
--- a/src/racket/src/schminc.h
+++ b/src/racket/src/schminc.h
@@ -15,7 +15,7 @@
 #define USE_COMPILED_STARTUP 1
 
 #define EXPECTED_PRIM_COUNT 1073
-#define EXPECTED_UNSAFE_COUNT 79
+#define EXPECTED_UNSAFE_COUNT 80
 #define EXPECTED_FLFXNUM_COUNT 69
 #define EXPECTED_FUTURES_COUNT 15
 
diff --git a/src/racket/src/schpriv.h b/src/racket/src/schpriv.h
index fb9ecc3d4d..3559f60f46 100644
--- a/src/racket/src/schpriv.h
+++ b/src/racket/src/schpriv.h
@@ -361,6 +361,7 @@ extern Scheme_Object *scheme_procedure_arity_includes_proc;
 extern Scheme_Object *scheme_void_proc;
 extern Scheme_Object *scheme_pair_p_proc;
 extern Scheme_Object *scheme_mpair_p_proc;
+extern Scheme_Object *scheme_unsafe_cons_list_proc;
 extern Scheme_Object *scheme_unsafe_car_proc;
 extern Scheme_Object *scheme_unsafe_cdr_proc;
 extern Scheme_Object *scheme_unsafe_mcar_proc;
diff --git a/src/racket/src/schvers.h b/src/racket/src/schvers.h
index a094996869..c3e4dbf795 100644
--- a/src/racket/src/schvers.h
+++ b/src/racket/src/schvers.h
@@ -13,12 +13,12 @@
    consistently.)
 */
 
-#define MZSCHEME_VERSION "5.3.1.5"
+#define MZSCHEME_VERSION "5.3.1.6"
 
 #define MZSCHEME_VERSION_X 5
 #define MZSCHEME_VERSION_Y 3
 #define MZSCHEME_VERSION_Z 1
-#define MZSCHEME_VERSION_W 5
+#define MZSCHEME_VERSION_W 6
 
 #define MZSCHEME_VERSION_MAJOR ((MZSCHEME_VERSION_X * 100) + MZSCHEME_VERSION_Y)
 #define MZSCHEME_VERSION_MINOR ((MZSCHEME_VERSION_Z * 1000) + MZSCHEME_VERSION_W)