Remove "Ord FastString" instance

FastStrings can be compared in 2 ways: by Unique or lexically. We don't
want to bless one particular way with an "Ord" instance because it leads
to bugs (#18562) or to suboptimal code (e.g. using lexical comparison
while a Unique comparison would suffice).

UTF-8 encoding has the advantage that sorting strings by their encoded
bytes also sorts them by their Unicode code points, without having to
decode the actual code points. BUT GHC uses Modified UTF-8 which
diverges from UTF-8 by encoding \0 as 0xC080 instead of 0x00 (to avoid
null bytes in the middle of a String so that the string can still be
null-terminated). This patch adds a new `utf8CompareShortByteString`
function that performs sorting by bytes but that also takes Modified
UTF-8 into account. It is much more performant than decoding the strings
into [Char] to perform comparisons (which we did in the previous patch).

Bump haddock submodule

1 files changed, 6 insertions, 7 deletions

diff --git a/compiler/GHC/Unit/State.hs b/compiler/GHC/Unit/State.hs
index 6e3a53310c..c95c9e4031 100644
--- a/compiler/GHC/Unit/State.hs
+++ b/compiler/GHC/Unit/State.hs
@@ -415,7 +415,7 @@ data UnitState = UnitState {
 
   -- | A mapping of 'PackageName' to 'IndefUnitId'.  This is used when
   -- users refer to packages in Backpack includes.
-  packageNameMap            :: Map PackageName IndefUnitId,
+  packageNameMap            :: UniqFM PackageName IndefUnitId,
 
   -- | A mapping from database unit keys to wired in unit ids.
   wireMap :: Map UnitId UnitId,
@@ -460,7 +460,7 @@ emptyUnitState :: UnitState
 emptyUnitState = UnitState {
     unitInfoMap = Map.empty,
     preloadClosure = emptyUniqSet,
-    packageNameMap = Map.empty,
+    packageNameMap = emptyUFM,
     wireMap   = Map.empty,
     unwireMap = Map.empty,
     preloadUnits = [],
@@ -533,7 +533,7 @@ unsafeLookupUnitId state uid = case lookupUnitId state uid of
 -- | Find the unit we know about with the given package name (e.g. @foo@), if any
 -- (NB: there might be a locally defined unit name which overrides this)
 lookupPackageName :: UnitState -> PackageName -> Maybe IndefUnitId
-lookupPackageName pkgstate n = Map.lookup n (packageNameMap pkgstate)
+lookupPackageName pkgstate n = lookupUFM (packageNameMap pkgstate) n
 
 -- | Search for units with a given package ID (e.g. \"foo-0.1\")
 searchPackageId :: UnitState -> PackageId -> [UnitInfo]
@@ -1587,10 +1587,9 @@ mkUnitState ctx printer cfg = do
                 -- likely to actually happen.
                 return (updateVisibilityMap wired_map plugin_vis_map2)
 
-  let pkgname_map = foldl' add Map.empty pkgs2
-        where add pn_map p
-                = Map.insert (unitPackageName p) (unitInstanceOf p) pn_map
-
+  let pkgname_map = listToUFM [ (unitPackageName p, unitInstanceOf p)
+                              | p <- pkgs2
+                              ]
   -- The explicitUnits accurately reflects the set of units we have turned
   -- on; as such, it also is the only way one can come up with requirements.
   -- The requirement context is directly based off of this: we simply