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author | Ömer Sinan Ağacan <omeragacan@gmail.com> | 2020-02-18 09:38:27 +0300 |
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committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2020-02-29 05:08:36 -0500 |
commit | b5fb58fd1a4a24b9273d9d2de65b6347e1654e98 (patch) | |
tree | eec82775f0414f77d5444cd9e25a2885ba378a6e /compiler | |
parent | a999ee96a22650b59855609f84e2808b4133e9e0 (diff) | |
download | haskell-b5fb58fd1a4a24b9273d9d2de65b6347e1654e98.tar.gz |
Document and refactor a few things around bitmap scavenging
- Added a few comments in StgPAP
- Added a few comments and assertions in scavenge_small_bitmap and
walk_large_bitmap
- Did tiny refactor in GHC.Data.Bitmap: added some comments, deleted
dead code, used PlatformWordSize type.
Diffstat (limited to 'compiler')
-rw-r--r-- | compiler/GHC/Data/Bitmap.hs | 43 |
1 files changed, 7 insertions, 36 deletions
diff --git a/compiler/GHC/Data/Bitmap.hs b/compiler/GHC/Data/Bitmap.hs index 1b93d6000d..985e74deb9 100644 --- a/compiler/GHC/Data/Bitmap.hs +++ b/compiler/GHC/Data/Bitmap.hs @@ -10,16 +10,15 @@ module GHC.Data.Bitmap ( Bitmap, mkBitmap, - intsToBitmap, intsToReverseBitmap, + intsToReverseBitmap, mAX_SMALL_BITMAP_SIZE, - seqBitmap, ) where import GhcPrelude +import GHC.Platform import GHC.Runtime.Heap.Layout import GHC.Driver.Session -import Util import Data.Bits @@ -43,31 +42,6 @@ chunkToBitmap dflags chunk = oneAt :: Int -> StgWord oneAt i = toStgWord dflags 1 `shiftL` i --- | Make a bitmap where the slots specified are the /ones/ in the bitmap. --- eg. @[0,1,3], size 4 ==> 0xb@. --- --- The list of @Int@s /must/ be already sorted. -intsToBitmap :: DynFlags - -> Int -- ^ size in bits - -> [Int] -- ^ sorted indices of ones - -> Bitmap -intsToBitmap dflags size = go 0 - where - word_sz = wORD_SIZE_IN_BITS dflags - oneAt :: Int -> StgWord - oneAt i = toStgWord dflags 1 `shiftL` i - - -- It is important that we maintain strictness here. - -- See Note [Strictness when building Bitmaps]. - go :: Int -> [Int] -> Bitmap - go !pos slots - | size <= pos = [] - | otherwise = - (foldl' (.|.) (toStgWord dflags 0) (map (\i->oneAt (i - pos)) these)) : - go (pos + word_sz) rest - where - (these,rest) = span (< (pos + word_sz)) slots - -- | Make a bitmap where the slots specified are the /zeros/ in the bitmap. -- eg. @[0,1,3], size 4 ==> 0x4@ (we leave any bits outside the size as zero, -- just to make the bitmap easier to read). @@ -101,7 +75,7 @@ intsToReverseBitmap dflags size = go 0 {- Note [Strictness when building Bitmaps] -======================================== +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ One of the places where @Bitmap@ is used is in in building Static Reference Tables (SRTs) (in @GHC.Cmm.Info.Build.procpointSRT@). In #7450 it was noticed @@ -125,10 +99,7 @@ large. This value represents the largest size of bitmap that can be packed into a single word. -} mAX_SMALL_BITMAP_SIZE :: DynFlags -> Int -mAX_SMALL_BITMAP_SIZE dflags - | wORD_SIZE dflags == 4 = 27 - | otherwise = 58 - -seqBitmap :: Bitmap -> a -> a -seqBitmap = seqList - +mAX_SMALL_BITMAP_SIZE dflags = + case platformWordSize (targetPlatform dflags) of + PW4 -> 27 -- On 32-bit: 5 bits for size, 27 bits for bitmap + PW8 -> 58 -- On 64-bit: 6 bits for size, 58 bits for bitmap |