diff options
Diffstat (limited to 'compiler/utils/Pretty.hs')
| -rw-r--r-- | compiler/utils/Pretty.hs | 61 |
1 files changed, 60 insertions, 1 deletions
diff --git a/compiler/utils/Pretty.hs b/compiler/utils/Pretty.hs index f4987d3751..9a12c7dae9 100644 --- a/compiler/utils/Pretty.hs +++ b/compiler/utils/Pretty.hs @@ -72,7 +72,7 @@ module Pretty ( -- ** Converting values into documents char, text, ftext, ptext, ztext, sizedText, zeroWidthText, - int, integer, float, double, rational, + int, integer, float, double, rational, hex, -- ** Simple derived documents semi, comma, colon, space, equals, @@ -117,6 +117,7 @@ import BufWrite import FastString import Panic import System.IO +import Numeric (showHex) --for a RULES import GHC.Base ( unpackCString# ) @@ -404,11 +405,18 @@ integer :: Integer -> Doc -- ^ @integer n = text (show n)@ float :: Float -> Doc -- ^ @float n = text (show n)@ double :: Double -> Doc -- ^ @double n = text (show n)@ rational :: Rational -> Doc -- ^ @rational n = text (show n)@ +hex :: Integer -> Doc -- ^ See Note [Print Hexadecimal Literals] int n = text (show n) integer n = text (show n) float n = text (show n) double n = text (show n) rational n = text (show n) +hex n = text ('0' : 'x' : padded) + where + str = showHex n "" + strLen = max 1 (length str) + len = 2 ^ (ceiling (logBase 2 (fromIntegral strLen :: Double)) :: Int) + padded = replicate (len - strLen) '0' ++ str parens :: Doc -> Doc -- ^ Wrap document in @(...)@ brackets :: Doc -> Doc -- ^ Wrap document in @[...]@ @@ -423,6 +431,57 @@ parens p = char '(' <> p <> char ')' brackets p = char '[' <> p <> char ']' braces p = char '{' <> p <> char '}' +{- +Note [Print Hexadecimal Literals] + +Relevant discussions: + * Phabricator: https://phabricator.haskell.org/D4465 + * GHC Trac: https://ghc.haskell.org/trac/ghc/ticket/14872 + +There is a flag `-dword-hex-literals` that causes literals of +type `Word#` or `Word64#` to be displayed in hexadecimal instead +of decimal when dumping GHC core. It also affects the presentation +of these in GHC's error messages. Additionally, the hexadecimal +encoding of these numbers is zero-padded so that its length is +a power of two. As an example of what this does, +consider the following haskell file `Literals.hs`: + + module Literals where + + alpha :: Int + alpha = 100 + 200 + + beta :: Word -> Word + beta x = x + div maxBound 255 + div 0xFFFFFFFF 255 + 0x0202 + +We get the following dumped core when we compile on a 64-bit +machine with ghc -O2 -fforce-recomp -ddump-simpl -dsuppress-all +-dhex-word-literals literals.hs: + + ==================== Tidy Core ==================== + + ... omitted for brevity ... + + -- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0} + alpha + alpha = I# 300# + + -- RHS size: {terms: 12, types: 3, coercions: 0, joins: 0/0} + beta + beta + = \ x_aYE -> + case x_aYE of { W# x#_a1v0 -> + W# + (plusWord# + (plusWord# (plusWord# x#_a1v0 0x0101010101010101##) 0x01010101##) + 0x0202##) + } + +Notice that the word literals are in hexadecimals and that they have +been padded with zeroes so that their lengths are 16, 8, and 4, respectively. + +-} + -- | Apply 'parens' to 'Doc' if boolean is true. maybeParens :: Bool -> Doc -> Doc maybeParens False = id |