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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2017-02-23 14:41:08 +0000 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2017-02-24 09:04:46 +0000 |
| commit | a6e13d502ef46de854ec1babcd764ccce68c95e3 (patch) | |
| tree | f6ace9b7af1b394546a885f1b2bb0699b67ccc37 /libraries/ghc-prim | |
| parent | c88b7c9a06e387c3b9bdb359b9e1e4f3a9fba696 (diff) | |
| download | haskell-a6e13d502ef46de854ec1babcd764ccce68c95e3.tar.gz | |
Make exprIsConApp_maybe work better for literals strings
There are two things here
* Use exprIsLiteral_maybe to "look through" a variable bound
to a literal string.
* Add CONLIKE to the NOINLINE pragma for unpackCString# and
unpackCStringUtf8#
See Trac #13317, Trac #10844, and
Note [exprIsConApp_maybe on literal strings] in CoreSubst
I did a nofib run and got essentially zero change except for one
2.2% improvement in allocation for 'pretty'.
Diffstat (limited to 'libraries/ghc-prim')
| -rw-r--r-- | libraries/ghc-prim/GHC/CString.hs | 21 |
1 files changed, 16 insertions, 5 deletions
diff --git a/libraries/ghc-prim/GHC/CString.hs b/libraries/ghc-prim/GHC/CString.hs index 19e6f75b1f..2adb13d8a0 100644 --- a/libraries/ghc-prim/GHC/CString.hs +++ b/libraries/ghc-prim/GHC/CString.hs @@ -34,9 +34,8 @@ import GHC.Prim -- stuff uses Strings in the representation, so to give representations for -- ghc-prim types we need unpackCString# -{- -Note [Inlining unpackCString#] -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +{- Note [Inlining unpackCString#] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ There's really no point in ever inlining things like unpackCString# as the loop doesn't specialise in an interesting way and we can't deforest the list constructors (we'd want to use unpackFoldrCString# for this). Moreover, it's @@ -57,10 +56,22 @@ to match unpackCString#, * stream fusion rules; e.g. in the `text` library, unstream (S.map safe (S.streamList (GHC.unpackCString# a))) = unpackCString# a + +Moreover, we want to make it CONLIKE, so that: + +* the rules in PrelRules will fire when the string is let-bound. + E.g. the eqString rule in PrelRules + eqString (unpackCString# (Lit s1)) (unpackCString# (Lit s2) = s1==s2 + +* exprIsConApp_maybe will see the string when we ahve + let x = unpackCString# "foo"# + ...(case x of algs)... + +All of this goes for unpackCStringUtf8# too. -} unpackCString# :: Addr# -> [Char] -{-# NOINLINE unpackCString# #-} +{-# NOINLINE CONLIKE unpackCString# #-} unpackCString# addr = unpack 0# where @@ -110,7 +121,7 @@ unpackFoldrCString# addr f z -- There's really no point in inlining this for the same reasons as -- unpackCString. See Note [Inlining unpackCString#] above for details. unpackCStringUtf8# :: Addr# -> [Char] -{-# NOINLINE unpackCStringUtf8# #-} +{-# NOINLINE CONLIKE unpackCStringUtf8# #-} unpackCStringUtf8# addr = unpack 0# where |