X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=rts%2Fsm%2FBlockAlloc.c;h=280ebfc7dbdfb94bbe3f5757771572916b34fe8d;hb=1e9af42caa0949ae05e5e2db5250227e86196e19;hp=daf9fb0ba166efe16ecbbb8a0368e42025ce5e3d;hpb=43a120b706a5eece6624ca4907af89fc9a480c5e;p=ghc-hetmet.git

diff --git a/rts/sm/BlockAlloc.c b/rts/sm/BlockAlloc.c
index daf9fb0..280ebfc 100644
--- a/rts/sm/BlockAlloc.c
+++ b/rts/sm/BlockAlloc.c
@@ -565,6 +565,9 @@ freeChain_lock(bdescr *bd)
     RELEASE_SM_LOCK;
 }
 
+// splitBlockGroup(bd,B) splits bd in two.  Afterward, bd will have B
+// blocks, and a new block descriptor pointing to the remainder is
+// returned.
 bdescr *
 splitBlockGroup (bdescr *bd, nat blocks)
 {
@@ -575,16 +578,21 @@ splitBlockGroup (bdescr *bd, nat blocks)
     }
 
     if (bd->blocks > BLOCKS_PER_MBLOCK) {
-        nat mblocks;
+        nat low_mblocks, high_mblocks;
         void *new_mblock;
         if ((blocks - BLOCKS_PER_MBLOCK) % (MBLOCK_SIZE / BLOCK_SIZE) != 0) {
             barf("splitLargeBlock: not a multiple of a megablock");
         }
-        mblocks = 1 + (blocks - BLOCKS_PER_MBLOCK) / (MBLOCK_SIZE / BLOCK_SIZE);
-        new_mblock = (void *) ((P_)MBLOCK_ROUND_DOWN(bd) + mblocks * MBLOCK_SIZE_W);
+        low_mblocks = 1 + (blocks - BLOCKS_PER_MBLOCK) / (MBLOCK_SIZE / BLOCK_SIZE);
+        high_mblocks = (bd->blocks - blocks) / (MBLOCK_SIZE / BLOCK_SIZE);
+
+        new_mblock = (void *) ((P_)MBLOCK_ROUND_DOWN(bd) + low_mblocks * MBLOCK_SIZE_W);
         initMBlock(new_mblock);
         new_bd = FIRST_BDESCR(new_mblock);
-        new_bd->blocks = MBLOCK_GROUP_BLOCKS(mblocks);
+        new_bd->blocks = MBLOCK_GROUP_BLOCKS(high_mblocks);
+
+        ASSERT(blocks + new_bd->blocks == 
+               bd->blocks + BLOCKS_PER_MBLOCK - MBLOCK_SIZE/BLOCK_SIZE);
     }
     else
     {