[project @ 2001-07-23 17:23:19 by simonmar]

Add a compacting garbage collector.

It isn't enabled by default, as there are still a couple of problems:
there's a fallback case I haven't implemented yet which means it will
occasionally bomb out, and speed-wise it's quite a bit slower than the
copying collector (about 1.8x slower).

Until I can make it go faster, it'll only be useful when you're
actually running low on real memory.

'+RTS -c' to enable it.

Oh, and I cleaned up a few things in the RTS while I was there, and
fixed one or two possibly real bugs in the existing GC.

1 files changed, 30 insertions, 0 deletions

diff --git a/ghc/rts/GCCompact.h b/ghc/rts/GCCompact.h
new file mode 100644
index 0000000000..8244e87c45
--- /dev/null
+++ b/ghc/rts/GCCompact.h
@@ -0,0 +1,30 @@
+/* -----------------------------------------------------------------------------
+ * $Id: GCCompact.h,v 1.1 2001/07/23 17:23:19 simonmar Exp $
+ *
+ * (c) The GHC Team 1998-1999
+ *
+ * Compacting garbage collector
+ *
+ * ---------------------------------------------------------------------------*/
+
+static inline void 
+mark(StgPtr p, bdescr *bd)
+{
+    nat offset_within_block = p - bd->start; // in words
+    StgPtr bitmap_word = (StgPtr)bd->u.bitmap + 
+	(offset_within_block / (sizeof(W_)*BITS_PER_BYTE));
+    nat bit_mask = 1 << (offset_within_block & (sizeof(W_)*BITS_PER_BYTE - 1));
+    *bitmap_word |= bit_mask;
+}
+
+static inline int
+is_marked(StgPtr p, bdescr *bd)
+{
+    nat offset_within_block = p - bd->start; // in words
+    StgPtr bitmap_word = (StgPtr)bd->u.bitmap + 
+	(offset_within_block / (sizeof(W_)*BITS_PER_BYTE));
+    nat bit_mask = 1 << (offset_within_block & (sizeof(W_)*BITS_PER_BYTE - 1));
+    return (*bitmap_word & bit_mask);
+}
+
+void compact( void (*get_roots)(evac_fn) );