From 339b1b6466434a57bfbea069ab5aedf3ffa7d16a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Lindqvist?= <bjourne@gmail.com>
Date: Wed, 9 Dec 2015 21:31:13 +0100
Subject: [PATCH] VM: put the singletons t, -1, 0 and 1 in the special objects
 table

Having them there instead of as fields in the vm struct removes a bunch
of special handling. This commit just adds them and doesn't remove the
old ones to avoid potential chicken-and-egg bootstrap problems.
---
 basis/bootstrap/image/image-tests.factor | 22 +++++++++++++++++++++-
 basis/bootstrap/image/image.factor       |  8 ++++++++
 core/kernel/kernel.factor                |  9 +++++++--
 vm/objects.hpp                           | 15 +++++++++++++--
 4 files changed, 49 insertions(+), 5 deletions(-)

diff --git a/basis/bootstrap/image/image-tests.factor b/basis/bootstrap/image/image-tests.factor
index 2e91ce4099..d41d676ca9 100644
--- a/basis/bootstrap/image/image-tests.factor
+++ b/basis/bootstrap/image/image-tests.factor
@@ -31,6 +31,26 @@ IN: bootstrap.image.tests
     H{ } [ special-objects set emit-jit-data ] keep assoc-size
 ] unit-test
 
-{ 90 } [
+{ 95 } [
     50 <vector> [ bootstrapping-image set emit-image-header ] keep length
 ] unit-test
+
+! emit-bignum
+{ V{
+    ! 33 bignum
+    32 0 33
+    ! -108 bignum
+    32 1 108
+} } [
+    V{ } bootstrapping-image set
+    33 emit-bignum
+    -108 emit-bignum
+    bootstrapping-image get
+] unit-test
+
+! prepare-object - what does this mean?
+{ 269 } [
+    V{ } clone bootstrapping-image set
+    H{ } clone objects set
+    55 >bignum prepare-object
+] unit-test
diff --git a/basis/bootstrap/image/image.factor b/basis/bootstrap/image/image.factor
index e407d0399f..44d8e5cf17 100755
--- a/basis/bootstrap/image/image.factor
+++ b/basis/bootstrap/image/image.factor
@@ -433,6 +433,12 @@ M: quotation prepare-object
 : emit-words ( -- )
     all-words [ emit-word ] each ;
 
+: emit-singletons ( -- )
+    t OBJ-CANONICAL-TRUE special-objects get set-at
+    0 >bignum OBJ-BIGNUM-ZERO special-objects get set-at
+    1 >bignum OBJ-BIGNUM-POS-ONE special-objects get set-at
+    -1 >bignum OBJ-BIGNUM-NEG-ONE special-objects get set-at ;
+
 : emit-global ( -- )
     {
         dictionary source-files builtins
@@ -497,6 +503,8 @@ M: quotation prepare-object
     emit-jit-data
     "Serializing global namespace..." print flush
     emit-global
+    "Serializing singletons..." print flush
+    emit-singletons
     "Serializing special object table..." print flush
     emit-special-objects
     "Performing word fixups..." print flush
diff --git a/core/kernel/kernel.factor b/core/kernel/kernel.factor
index 611ba18d97..7821a6abea 100644
--- a/core/kernel/kernel.factor
+++ b/core/kernel/kernel.factor
@@ -309,8 +309,7 @@ ERROR: assert got expect ;
 
 ! Special object count and identifiers must be kept in sync with:
 !   vm/objects.hpp
-!   basis/bootstrap/image/image.factor
-CONSTANT: special-object-count 80
+CONSTANT: special-object-count 85
 
 CONSTANT: OBJ-WALKER-HOOK 3
 
@@ -409,6 +408,12 @@ CONSTANT: OBJ-VM-COMPILE-TIME 75
 CONSTANT: OBJ-VM-VERSION 76
 CONSTANT: OBJ-VM-GIT-LABEL 77
 
+CONSTANT: OBJ-CANONICAL-TRUE 78
+
+CONSTANT: OBJ-BIGNUM-ZERO 79
+CONSTANT: OBJ-BIGNUM-POS-ONE 80
+CONSTANT: OBJ-BIGNUM-NEG-ONE 81
+
 ! Context object count and identifiers must be kept in sync with:
 !   vm/contexts.hpp
 
diff --git a/vm/objects.hpp b/vm/objects.hpp
index 9696be2627..dc29b0382a 100644
--- a/vm/objects.hpp
+++ b/vm/objects.hpp
@@ -4,7 +4,7 @@ namespace factor {
 //   core/kernel/kernel.factor
 //   basis/bootstrap/image/image.factor
 
-static const cell special_object_count = 80;
+static const cell special_object_count = 85;
 
 enum special_object {
   OBJ_WALKER_HOOK = 3, /* non-local exit hook, used by library only */
@@ -110,6 +110,15 @@ enum special_object {
   OBJ_VM_COMPILE_TIME = 75, /* when the binary was built */
   OBJ_VM_VERSION = 76, /* factor version */
   OBJ_VM_GIT_LABEL = 77, /* git label (git describe --all --long) */
+
+  /* Canonical truth value. In Factor, 't' */
+  OBJ_CANONICAL_TRUE = 78,
+
+  /* Canonical bignums. These needs to be kept in the image in case
+     some heap objects refer to them. */
+  OBJ_BIGNUM_ZERO,
+  OBJ_BIGNUM_POS_ONE,
+  OBJ_BIGNUM_NEG_ONE = 81,
 };
 
 /* save-image-and-exit discards special objects that are filled in on startup
@@ -118,7 +127,9 @@ enum special_object {
 #define OBJ_LAST_SAVE OBJ_STAGE2
 
 inline static bool save_special_p(cell i) {
-  return (i >= OBJ_FIRST_SAVE && i <= OBJ_LAST_SAVE);
+  /* Need to fix the order here. */
+  return (i >= OBJ_FIRST_SAVE && i <= OBJ_LAST_SAVE) ||
+      (i >= OBJ_CANONICAL_TRUE);
 }
 
 template <typename Iterator> void object::each_slot(Iterator& iter) {