From b2301406c44ca423f6e0d93b4650a2748188d725 Mon Sep 17 00:00:00 2001
From: Vincent St-Amour <stamourv@iro.umontreal.ca>
Date: Tue, 9 Feb 2010 19:28:29 -0500
Subject: [PATCH] Since we don't use closures as pairs in the stack anymore,
 the environment pointer in closures has been moved to the car, to simplify
 gc.

---
 dispatch.c   | 22 +++++++++++-----------
 gc.c         | 22 ++--------------------
 picobit-vm.c | 10 ++++------
 picobit-vm.h |  7 +------
 primitives.c |  6 +++---
 5 files changed, 21 insertions(+), 46 deletions(-)

diff --git a/dispatch.c b/dispatch.c
index 7fa01b6..d1edaa7 100644
--- a/dispatch.c
+++ b/dispatch.c
@@ -42,7 +42,7 @@ uint8 handle_arity_and_rest_param (uint8 na) {
   np = rom_get (entry++);
 
   if (arg1 != OBJ_NULL)
-    arg1 = ram_get_cdr(arg1); // closed environment
+    arg1 = ram_get_car(arg1); // closed environment
 
   if ((np & 0x80) == 0) {
     if (na != np)
@@ -86,10 +86,10 @@ uint8 build_env (uint8 na) {
 
 void save_cont () {
   // the second half is a closure
-  arg3 = alloc_ram_cell_init (CLOSURE_FIELD0 | (pc >> 11),
-                              (pc >> 3) & 0xff,
-                              ((pc & 0x0007) << 5) | (env >> 8),
-                              env & 0xff);
+  arg3 = alloc_ram_cell_init (CLOSURE_FIELD0 | (env >> 8),
+			      env & 0xff,
+                              (pc >> 8),
+                              (pc & 0xff));
   cont = alloc_ram_cell_init (COMPOSITE_FIELD0 | (cont >> 8),
                               cont & 0xff,
                               CONTINUATION_FIELD2 | (arg3 >> 8),
@@ -311,10 +311,10 @@ void interpreter () {
 
       arg3 = pop(); // env
 
-      arg1 = alloc_ram_cell_init (CLOSURE_FIELD0 | (entry >> 11),
-                                  entry >> 3,
-                                  ((entry & 0x07) <<5) | ((arg3 >> 8) & 0x1f),
-                                  arg3 & 0xff);
+      arg1 = alloc_ram_cell_init (CLOSURE_FIELD0 | (arg3 >> 8),
+				  arg3 & 0xff,
+                                  entry >> 8,
+                                  (entry & 0xff));
 
       push_arg1();
 
@@ -575,7 +575,7 @@ void interpreter () {
 
       pc = ram_get_entry (arg2);
 
-      env = ram_get_cdr (arg2);
+      env = ram_get_car (arg2);
       cont = ram_get_car (cont);
 
       push_arg1();
@@ -674,7 +674,7 @@ void interpreter () {
       arg1 = pop();
       arg2 = ram_get_cdr (cont);
       pc = ram_get_entry (arg2);
-      env = ram_get_cdr (arg2);
+      env = ram_get_car (arg2);
       cont = ram_get_car (cont);
       push_arg1();
       arg2 = OBJ_FALSE;
diff --git a/gc.c b/gc.c
index d658f92..1d8f5b7 100644
--- a/gc.c
+++ b/gc.c
@@ -87,18 +87,12 @@ void mark (obj temp) {
       visit_field1:
 
 	// closures have the pointer in the cdr, not in the car as others
-	if (RAM_CLOSURE(visit))
-	  temp = ram_get_cdr (visit);
-	else
-	  temp = ram_get_car (visit);
+	temp = ram_get_car (visit);
 	
 	if (IN_RAM(temp)) {
 	  IF_GC_TRACE(printf ("case 6\n"));
 	  ram_set_gc_tag0 (visit, GC_TAG_0_LEFT);
-	  if (RAM_CLOSURE(visit))
-	    ram_set_cdr (visit, stack);
-	  else 
-	    ram_set_car (visit, stack);		  
+	  ram_set_car (visit, stack);		  
 	  
 	  goto push;
 	}
@@ -130,18 +124,6 @@ void mark (obj temp) {
 	goto visit_field1;
       }
 
-      if (RAM_CLOSURE(stack)) {
-	// closures have one object field, but it's in the cdr
-	IF_GC_TRACE(printf ("case 10\n"));
-	
-	temp = ram_get_cdr (stack);  /* pop through cdr */
-	ram_set_cdr (stack, visit);
-	visit = stack;
-	stack = temp;
-	
-	goto pop;
-      }
-      
       IF_GC_TRACE(printf ("case 11\n"));
       
       temp = ram_get_car (stack);  /* pop through car */
diff --git a/picobit-vm.c b/picobit-vm.c
index d7ba1f5..81bd323 100644
--- a/picobit-vm.c
+++ b/picobit-vm.c
@@ -92,14 +92,12 @@ void ram_set_cdr (obj o, obj val) {
 // function entry point
 // the temporary variables are necessary with SIXPIC, see above
 obj ram_get_entry (obj o) {
-  uint16 tmp  = ram_get_field0 (o) & 0x1f;
-  uint16 tmp2 = ram_get_field1 (o);
-  return ((tmp << 11) | (tmp2 << 3) | (ram_get_field2 (o) >> 5));
+  uint16 tmp  = ram_get_field2 (o);
+  return ((tmp << 8) | ram_get_field3 (o));
 }
 obj rom_get_entry (obj o){
-  uint16 tmp  = rom_get_field0 (o) & 0x1f;
-  uint16 tmp2 = rom_get_field1 (o);
-  return ((tmp << 11) | (tmp2 << 3) | (rom_get_field2 (o) >> 5));
+  uint16 tmp  = rom_get_field2 (o);
+  return ((tmp << 8) | rom_get_field3 (o));
 }
 
 obj get_global (uint8 i) {
diff --git a/picobit-vm.h b/picobit-vm.h
index a9568be..032027d 100644
--- a/picobit-vm.h
+++ b/picobit-vm.h
@@ -378,14 +378,9 @@ void set_global (uint8 i, obj o);
   x is length of the vector, in bytes (stored raw, not encoded as an object)
   y is pointer to the elements themselves (stored in vector space)
 
-  closure      01Gaaaaa aaaaaaaa aaaxxxxx xxxxxxxx
+  closure      01Gxxxxx xxxxxxxx aaaaaaaa aaaaaaaa
   0x5ff<a<0x4000 is entry
   x is pointer to environment
-  the reason why the environment is on the cdr (and the entry is split on 3
-  bytes) is that, when looking for a variable, a closure is considered to be a
-  pair. The compiler adds an extra offset to any variable in the closure's
-  environment, so the car of the closure (which doesn't really exist) is never
-  checked, but the cdr is followed to find the other bindings
   
   continuation 1GGxxxxx xxxxxxxx 100yyyyy yyyyyyyy
   x is parent continuation
diff --git a/primitives.c b/primitives.c
index bb9d2b2..7d263f2 100644
--- a/primitives.c
+++ b/primitives.c
@@ -555,10 +555,10 @@ void show (obj o) {
       obj env;
       rom_addr pc;
       
-      if (IN_RAM(o))
-	env = ram_get_cdr (o);
+      if (IN_RAM(o)) // TODO remove code for ROM closures
+	env = ram_get_car (o);
       else
-	env = rom_get_cdr (o);
+	env = rom_get_car (o);
       
       if (IN_RAM(o))
 	pc = ram_get_entry (o);
-- 
2.11.4.GIT