Fix two issues in stg_newArrayzh

The implementations of newArray# and newArrayArray#, stg_newArrayzh
and stg_newArrayArrayzh, had three issues:

 * The condition for the loop that fills the array with the initial
   element was incorrect. It would write into the card table as
   well. The condition for the loop that filled the card table was
   never executed, as its condition was also wrong. In the end this
   didn't lead to any disasters as the value of the card table doesn't
   matter for newly allocated arrays.

 * The card table was unnecessarily initialized. The card table is
   only used when the array isn't copied, which new arrays always
   are. By not writing the card table at all we save some cycles.

 * The ticky allocation accounting was wrong. The second argument to
   TICK_ALLOC_PRIM is the size of the closure excluding the header
   size, but the header size was incorrectly included.

Fixes #8867.

1 files changed, 4 insertions, 18 deletions

diff --git a/rts/PrimOps.cmm b/rts/PrimOps.cmm
index db65a4a268..0e547be388 100644
--- a/rts/PrimOps.cmm
+++ b/rts/PrimOps.cmm
@@ -178,7 +178,7 @@ stg_newArrayzh ( W_ n /* words */, gcptr init )
     size = n + mutArrPtrsCardWords(n);
     words = BYTES_TO_WDS(SIZEOF_StgMutArrPtrs) + size;
     ("ptr" arr) = ccall allocate(MyCapability() "ptr",words);
-    TICK_ALLOC_PRIM(SIZEOF_StgMutArrPtrs, WDS(n), 0);
+    TICK_ALLOC_PRIM(SIZEOF_StgMutArrPtrs, WDS(size), 0);
 
     SET_HDR(arr, stg_MUT_ARR_PTRS_DIRTY_info, CCCS);
     StgMutArrPtrs_ptrs(arr) = n;
@@ -187,18 +187,11 @@ stg_newArrayzh ( W_ n /* words */, gcptr init )
     // Initialise all elements of the the array with the value in R2
     p = arr + SIZEOF_StgMutArrPtrs;
   for:
-    if (p < arr + WDS(words)) {
+    if (p < arr + SIZEOF_StgMutArrPtrs + WDS(n)) {
         W_[p] = init;
         p = p + WDS(1);
         goto for;
     }
-    // Initialise the mark bits with 0
-  for2:
-    if (p < arr + WDS(size)) {
-        W_[p] = 0;
-        p = p + WDS(1);
-        goto for2;
-    }
 
     return (arr);
 }
@@ -270,7 +263,7 @@ stg_newArrayArrayzh ( W_ n /* words */ )
     size = n + mutArrPtrsCardWords(n);
     words = BYTES_TO_WDS(SIZEOF_StgMutArrPtrs) + size;
     ("ptr" arr) = ccall allocate(MyCapability() "ptr",words);
-    TICK_ALLOC_PRIM(SIZEOF_StgMutArrPtrs, WDS(n), 0);
+    TICK_ALLOC_PRIM(SIZEOF_StgMutArrPtrs, WDS(size), 0);
 
     SET_HDR(arr, stg_MUT_ARR_PTRS_DIRTY_info, W_[CCCS]);
     StgMutArrPtrs_ptrs(arr) = n;
@@ -279,18 +272,11 @@ stg_newArrayArrayzh ( W_ n /* words */ )
     // Initialise all elements of the array with a pointer to the new array
     p = arr + SIZEOF_StgMutArrPtrs;
   for:
-    if (p < arr + WDS(words)) {
+    if (p < arr + SIZEOF_StgMutArrPtrs + WDS(n)) {
         W_[p] = arr;
         p = p + WDS(1);
         goto for;
     }
-    // Initialise the mark bits with 0
-  for2:
-    if (p < arr + WDS(size)) {
-        W_[p] = 0;
-        p = p + WDS(1);
-        goto for2;
-    }
 
     return (arr);
 }