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| author | Ben Gamari <ben@smart-cactus.org> | 2021-01-06 11:20:44 -0500 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2021-01-17 05:53:02 -0500 |
| commit | d159041b44049d87db7e26d09120e0b2633b3b3c (patch) | |
| tree | 5e6c92f9c03b703f8b1b100ebf18562a9409b144 | |
| parent | 84dcb8440e94fab5aaba66e613de27d89264f076 (diff) | |
| download | haskell-d159041b44049d87db7e26d09120e0b2633b3b3c.tar.gz | |
rts: Initialize card table in newArray#
Previously we would leave the card table of new arrays uninitialized.
This wasn't a soundness issue: at worst we would end up doing
unnecessary scavenging during GC, after which the card table would be
reset. That being said, it seems worth initializing this properly to
avoid both unnecessary work and non-determinism.
Fixes #19143.
| -rw-r--r-- | includes/Cmm.h | 33 | ||||
| -rw-r--r-- | rts/PrimOps.cmm | 3 |
2 files changed, 23 insertions, 13 deletions
diff --git a/includes/Cmm.h b/includes/Cmm.h index fdb4badf9a..84c6fca125 100644 --- a/includes/Cmm.h +++ b/includes/Cmm.h @@ -814,7 +814,7 @@ return (dst); #define copyArray(src, src_off, dst, dst_off, n) \ - W_ dst_elems_p, dst_p, src_p, dst_cards_p, bytes; \ + W_ dst_elems_p, dst_p, src_p, bytes; \ \ if ((n) != 0) { \ SET_HDR(dst, stg_MUT_ARR_PTRS_DIRTY_info, CCCS); \ @@ -826,14 +826,13 @@ \ prim %memcpy(dst_p, src_p, bytes, SIZEOF_W); \ \ - dst_cards_p = dst_elems_p + WDS(StgMutArrPtrs_ptrs(dst)); \ - setCards(dst_cards_p, dst_off, n); \ + setCards(dst, dst_off, n); \ } \ \ return (); #define copyMutableArray(src, src_off, dst, dst_off, n) \ - W_ dst_elems_p, dst_p, src_p, dst_cards_p, bytes; \ + W_ dst_elems_p, dst_p, src_p, bytes; \ \ if ((n) != 0) { \ SET_HDR(dst, stg_MUT_ARR_PTRS_DIRTY_info, CCCS); \ @@ -849,22 +848,30 @@ prim %memcpy(dst_p, src_p, bytes, SIZEOF_W); \ } \ \ - dst_cards_p = dst_elems_p + WDS(StgMutArrPtrs_ptrs(dst)); \ - setCards(dst_cards_p, dst_off, n); \ + setCards(dst, dst_off, n); \ } \ \ return (); /* - * Set the cards in the cards table pointed to by dst_cards_p for an + * Set the cards in the array pointed to by arr for an * update to n elements, starting at element dst_off. */ -#define setCards(dst_cards_p, dst_off, n) \ - W_ __start_card, __end_card, __cards; \ - __start_card = mutArrPtrCardDown(dst_off); \ - __end_card = mutArrPtrCardDown((dst_off) + (n) - 1); \ - __cards = __end_card - __start_card + 1; \ - prim %memset((dst_cards_p) + __start_card, 1, __cards, 1); +#define setCards(arr, dst_off, n) \ + setCardsValue(arr, dst_off, n, 1) + +/* + * Set the cards in the array pointed to by arr for an + * update to n elements, starting at element dst_off to value (0 to indicate + * clean, 1 to indicate dirty). + */ +#define setCardsValue(arr, dst_off, n, value) \ + W_ __start_card, __end_card, __cards, __dst_cards_p; \ + __dst_cards_p = (arr) + SIZEOF_StgMutArrPtrs + WDS(StgMutArrPtrs_ptrs(arr)); \ + __start_card = mutArrPtrCardDown(dst_off); \ + __end_card = mutArrPtrCardDown((dst_off) + (n) - 1); \ + __cards = __end_card - __start_card + 1; \ + prim %memset(__dst_cards_p + __start_card, (value), __cards, 1) /* Complete function body for the clone family of small (mutable) array ops. Defined as a macro to avoid function call overhead or diff --git a/rts/PrimOps.cmm b/rts/PrimOps.cmm index c5b232f09d..77296e20ae 100644 --- a/rts/PrimOps.cmm +++ b/rts/PrimOps.cmm @@ -408,6 +408,9 @@ stg_newArrayArrayzh ( W_ n /* words */ ) StgMutArrPtrs_ptrs(arr) = n; StgMutArrPtrs_size(arr) = size; + // Initialize card table to all-clean. + setCardsValue(arr, 0, n, 0); + // Initialise all elements of the array with a pointer to the new array p = arr + SIZEOF_StgMutArrPtrs; for: |