Improve accuracy of get/setAllocationCounter

Summary:
get/setAllocationCounter didn't take into account allocations in the
current block. This was known at the time, but it turns out to be
important to have more accuracy when using these in a fine-grained
way.

Test Plan:
New unit test to test incrementally larger allocaitons.  Before I got
results like this:

```
+0
+0
+0
+0
+0
+4096
+0
+0
+0
+0
+0
+4064
+0
+0
+4088
+4056
+0
+0
+0
+4088
+4096
+4056
+4096
```

Notice how the results aren't always monotonically increasing.  After
this patch:

```
+344
+416
+488
+560
+632
+704
+776
+848
+920
+992
+1064
+1136
+1208
+1280
+1352
+1424
+1496
+1568
+1640
+1712
+1784
+1856
+1928
+2000
+2072
+2144
```

Reviewers: hvr, erikd, simonmar, jrtc27, trommler

Reviewed By: simonmar

Subscribers: trommler, jrtc27, rwbarton, thomie, carter

Differential Revision: https://phabricator.haskell.org/D4363

1 files changed, 2 insertions, 2 deletions

diff --git a/compiler/codeGen/StgCmmForeign.hs b/compiler/codeGen/StgCmmForeign.hs
index b518c0790a..c1103e7d77 100644
--- a/compiler/codeGen/StgCmmForeign.hs
+++ b/compiler/codeGen/StgCmmForeign.hs
@@ -404,8 +404,8 @@ Opening the nursery corresponds to the following code:
 @
    tso = CurrentTSO;
    cn = CurrentNursery;
-   bdfree = CurrentNuresry->free;
-   bdstart = CurrentNuresry->start;
+   bdfree = CurrentNursery->free;
+   bdstart = CurrentNursery->start;
 
    // We *add* the currently occupied portion of the nursery block to
    // the allocation limit, because we will subtract it again in