diff options
Diffstat (limited to 'compiler/GHC/Utils/Ppr.hs')
| -rw-r--r-- | compiler/GHC/Utils/Ppr.hs | 50 |
1 files changed, 46 insertions, 4 deletions
diff --git a/compiler/GHC/Utils/Ppr.hs b/compiler/GHC/Utils/Ppr.hs index 3fa84850b8..8871f98cef 100644 --- a/compiler/GHC/Utils/Ppr.hs +++ b/compiler/GHC/Utils/Ppr.hs @@ -917,16 +917,26 @@ data Style , ribbonsPerLine :: Float -- ^ Ratio of line length to ribbon length } --- | The default style (@mode=PageMode, lineLength=100, ribbonsPerLine=1.5@). +-- | The default style (@mode=PageMode False, lineLength=100, ribbonsPerLine=1.5@). style :: Style -style = Style { lineLength = 100, ribbonsPerLine = 1.5, mode = PageMode } +style = Style { lineLength = 100, ribbonsPerLine = 1.5, mode = PageMode False } -- | Rendering mode. -data Mode = PageMode -- ^ Normal +data Mode = PageMode { asciiSpace :: Bool } -- ^ Normal | ZigZagMode -- ^ With zig-zag cuts | LeftMode -- ^ No indentation, infinitely long lines | OneLineMode -- ^ All on one line +-- | Can we output an ascii space character for spaces? +-- Mostly true, but not for e.g. UTF16 +-- See Note [putSpaces optimizations] for why we bother +-- to track this. +hasAsciiSpace :: Mode -> Bool +hasAsciiSpace mode = + case mode of + PageMode asciiSpace -> asciiSpace + _ -> False + -- | Render the @Doc@ to a String using the given @Style@. renderStyle :: Style -> Doc -> String renderStyle s = fullRender (mode s) (lineLength s) (ribbonsPerLine s) @@ -1034,6 +1044,20 @@ printDoc :: Mode -> Int -> Handle -> Doc -> IO () -- printDoc adds a newline to the end printDoc mode cols hdl doc = printDoc_ mode cols hdl (doc $$ text "") +{- Note [putSpaces optimizations] + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +When using dump flags a lot of what we are dumping ends up being whitespace. +This is especially true for Core/Stg dumps. Enough so that it's worth optimizing. + +Especially in the common case of writing to an UTF8 or similarly encoded file +where space is equal to ascii space we use hPutBuf to write a preallocated +buffer to the file. This avoids a fair bit of allocation. + +For other cases we fall back to the old and slow path for simplicity. + +-} + printDoc_ :: Mode -> Int -> Handle -> Doc -> IO () -- printDoc_ does not add a newline at the end, so that -- successive calls can output stuff on the same line @@ -1051,9 +1075,27 @@ printDoc_ mode pprCols hdl doc -- the I/O library's encoding layer. (#3398) put (ZStr s) next = hPutFZS hdl s >> next put (LStr s) next = hPutPtrString hdl s >> next - put (RStr n c) next = hPutStr hdl (replicate n c) >> next + put (RStr n c) next + | c == ' ' + = putSpaces n >> next + | otherwise + = hPutStr hdl (replicate n c) >> next + putSpaces n + -- If we use ascii spaces we are allowed to use hPutBuf + -- See Note [putSpaces optimizations] + | hasAsciiSpace mode + , n <= 100 + = hPutBuf hdl (Ptr spaces') n + | hasAsciiSpace mode + , n > 100 + = hPutBuf hdl (Ptr spaces') 100 >> putSpaces (n-100) + + | otherwise = hPutStr hdl (replicate n ' ') done = return () -- hPutChar hdl '\n' + -- 100 spaces, so we avoid the allocation of replicate n ' ' + spaces' = " "# + -- some versions of hPutBuf will barf if the length is zero hPutPtrString :: Handle -> PtrString -> IO () |