From 014bd392da9cd22a4057427dca70e314ce4d2667 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Sat, 6 Dec 2008 17:31:18 +0000
Subject: [PATCH] save a few instructions on mark-stack operations

svn: r12716
---
 src/mzscheme/gc2/newgc.c | 34 +++++++++++++++++++---------------
 1 file changed, 19 insertions(+), 15 deletions(-)

diff --git a/src/mzscheme/gc2/newgc.c b/src/mzscheme/gc2/newgc.c
index 229336d2f8..9350b12c27 100644
--- a/src/mzscheme/gc2/newgc.c
+++ b/src/mzscheme/gc2/newgc.c
@@ -1244,35 +1244,37 @@ typedef struct MarkSegment {
   struct MarkSegment *prev;
   struct MarkSegment *next;
   void **top;
-  void **end;
-  void *stop_here; /* this is only used for its address */
 } MarkSegment;
 
+#define MARK_STACK_START(ms) ((void **)(void *)&ms[1])
+#define MARK_STACK_END(ms) ((void **)((char *)ms + STACK_PART_SIZE))
+
 static THREAD_LOCAL MarkSegment *mark_stack = NULL;
 
 inline static MarkSegment* mark_stack_create_frame() {
   MarkSegment *mark_frame = (MarkSegment*)ofm_malloc(STACK_PART_SIZE);
   mark_frame->next = NULL;
-  mark_frame->top  = &(mark_frame->stop_here);
-  mark_frame->end  = PPTR(NUM(mark_frame) + STACK_PART_SIZE);
+  mark_frame->top  = MARK_STACK_START(mark_frame);
   return mark_frame;
 }
 
-inline static void push_ptr(void *ptr)
+inline static void init_mark_stack()
 {
-  /* This happens at the very beginning */
   if(!mark_stack) {
     mark_stack = mark_stack_create_frame();
     mark_stack->prev = NULL;
   }
+}
 
+inline static void push_ptr(void *ptr)
+{
   /* This happens during propoagation if we go past the end of this MarkSegment*/
-  if(mark_stack->top == mark_stack->end) {
+  if(mark_stack->top == MARK_STACK_END(mark_stack)) {
     /* test to see if we already have another stack page ready */
     if(mark_stack->next) {
       /* we do, so just use it */
       mark_stack = mark_stack->next;
-      mark_stack->top = &(mark_stack->stop_here);
+      mark_stack->top = MARK_STACK_START(mark_stack);
     } else {
       /* we don't, so we need to allocate one */
       mark_stack->next = mark_stack_create_frame();
@@ -1287,7 +1289,7 @@ inline static void push_ptr(void *ptr)
 
 inline static int pop_ptr(void **ptr)
 {
-  if(mark_stack->top == &mark_stack->stop_here) {
+  if(mark_stack->top == MARK_STACK_START(mark_stack)) {
     if(mark_stack->prev) {
       /* if there is a previous page, go to it */
       mark_stack = mark_stack->prev;
@@ -1323,7 +1325,7 @@ inline static void clear_stack_pages(void)
         free(mark_stack);
     }
     mark_stack = base;
-    mark_stack->top = PPTR(mark_stack) + 4;
+    mark_stack->top = MARK_STACK_START(mark_stack);
   }
 }
 
@@ -1332,7 +1334,7 @@ inline static void reset_pointer_stack(void)
   /* go to the head of the list */
   for(; mark_stack->prev; mark_stack = mark_stack->prev) {}
   /* reset the stack */
-  mark_stack->top = PPTR(mark_stack) + 4;
+  mark_stack->top = MARK_STACK_START(mark_stack);
 }
 
 /*****************************************************************************/
@@ -1424,6 +1426,8 @@ void NewGC_initialize(NewGC *newgc) {
   newgc->generations_available = 1;
   newgc->last_full_mem_use = (20 * 1024 * 1024);
   newgc->new_btc_mark = 1;
+
+  init_mark_stack();
 }
 
 void GC_init_type_tags(int count, int pair, int mutable_pair, int weakbox, int ephemeron, int weakarray, int custbox)
@@ -1558,7 +1562,7 @@ void GC_mark(const void *const_p)
       /* if we're doing memory accounting, then we need to make sure the
          btc_mark is right */
 #ifdef NEWGC_BTC_ACCOUNT
-        BTC_set_btc_mark(gc, PTR(NUM(page->addr) + PREFIX_SIZE));
+      BTC_set_btc_mark(gc, PTR(NUM(page->addr) + PREFIX_SIZE));
 #endif
     }
 
@@ -1655,11 +1659,11 @@ void GC_mark(const void *const_p)
       work->has_new = 1;
 
       /* transfer the object */
+      ohead->mark = 1; /* mark is copied to newplace, too */
       memcpy(newplace, (const void *)ohead, size);
       /* mark the old location as marked and moved, and the new location
          as marked */
-      ohead->mark = ohead->moved = 1;
-      ((struct objhead *)newplace)->mark = 1;
+      ohead->moved = 1;
       /* if we're doing memory accounting, then we need the btc_mark
          to be set properly */
 #ifdef NEWGC_BTC_ACCOUNT
@@ -1672,7 +1676,7 @@ void GC_mark(const void *const_p)
       record_backtrace(work, newplace);
       /* set forwarding pointer */
       GCDEBUG((DEBUGOUTF,"Marking %p (moved to %p on page %p)\n", 
-            p, newplace, work));
+               p, newplace, work));
       *(void**)p = newplace;
       push_ptr(newplace);
     }