Change `Backend` type and remove direct dependencieswip/backend-as-record

With this change, `Backend` becomes an abstract type
(there are no more exposed value constructors).
Decisions that were formerly made by asking "is the
current back end equal to (or different from) this named value
constructor?" are now made by interrogating the back end about
its properties, which are functions exported by `GHC.Driver.Backend`.

There is a description of how to migrate code using `Backend` in the
user guide.

Clients using the GHC API can find a backdoor to access the Backend
datatype in GHC.Driver.Backend.Internal.

Bumps haddock submodule.

Fixes #20927

1 files changed, 16 insertions, 28 deletions

diff --git a/compiler/GHC/SysTools/Tasks.hs b/compiler/GHC/SysTools/Tasks.hs
index 312ec7897a..a1846980a1 100644
--- a/compiler/GHC/SysTools/Tasks.hs
+++ b/compiler/GHC/SysTools/Tasks.hs
@@ -44,7 +44,7 @@ import System.Process
 -}
 
 runUnlit :: Logger -> DynFlags -> [Option] -> IO ()
-runUnlit logger dflags args = traceToolCommand logger "unlit" $ do
+runUnlit logger dflags args = traceSystoolCommand logger "unlit" $ do
   let prog = pgm_L dflags
       opts = getOpts dflags opt_L
   runSomething logger "Literate pre-processor" prog
@@ -60,7 +60,7 @@ augmentImports dflags ("-include":fp:fps) = "-include" : augmentByWorkingDirecto
 augmentImports dflags (fp1: fp2: fps) = fp1 : augmentImports dflags (fp2:fps)
 
 runCpp :: Logger -> DynFlags -> [Option] -> IO ()
-runCpp logger dflags args = traceToolCommand logger "cpp" $ do
+runCpp logger dflags args = traceSystoolCommand logger "cpp" $ do
   let opts = getOpts dflags opt_P
       modified_imports = augmentImports dflags opts
   let (p,args0) = pgm_P dflags
@@ -72,14 +72,14 @@ runCpp logger dflags args = traceToolCommand logger "cpp" $ do
                        (args0 ++ args1 ++ args2 ++ args) Nothing mb_env
 
 runPp :: Logger -> DynFlags -> [Option] -> IO ()
-runPp logger dflags args = traceToolCommand logger "pp" $ do
+runPp logger dflags args = traceSystoolCommand logger "pp" $ do
   let prog = pgm_F dflags
       opts = map Option (getOpts dflags opt_F)
   runSomething logger "Haskell pre-processor" prog (args ++ opts)
 
 -- | Run compiler of C-like languages and raw objects (such as gcc or clang).
 runCc :: Maybe ForeignSrcLang -> Logger -> TmpFs -> DynFlags -> [Option] -> IO ()
-runCc mLanguage logger tmpfs dflags args = traceToolCommand logger "cc" $ do
+runCc mLanguage logger tmpfs dflags args = traceSystoolCommand logger "cc" $ do
   let args1 = map Option userOpts
       args2 = languageOptions ++ args ++ args1
       -- We take care to pass -optc flags in args1 last to ensure that the
@@ -167,7 +167,7 @@ xs `isContainedIn` ys = any (xs `isPrefixOf`) (tails ys)
 
 -- | Run the linker with some arguments and return the output
 askLd :: Logger -> DynFlags -> [Option] -> IO String
-askLd logger dflags args = traceToolCommand logger "linker" $ do
+askLd logger dflags args = traceSystoolCommand logger "linker" $ do
   let (p,args0) = pgm_l dflags
       args1     = map Option (getOpts dflags opt_l)
       args2     = args0 ++ args1 ++ args
@@ -176,7 +176,7 @@ askLd logger dflags args = traceToolCommand logger "linker" $ do
     readCreateProcessWithExitCode' (proc p real_args){ env = mb_env }
 
 runAs :: Logger -> DynFlags -> [Option] -> IO ()
-runAs logger dflags args = traceToolCommand logger "as" $ do
+runAs logger dflags args = traceSystoolCommand logger "as" $ do
   let (p,args0) = pgm_a dflags
       args1 = map Option (getOpts dflags opt_a)
       args2 = args0 ++ args1 ++ args
@@ -185,7 +185,7 @@ runAs logger dflags args = traceToolCommand logger "as" $ do
 
 -- | Run the LLVM Optimiser
 runLlvmOpt :: Logger -> DynFlags -> [Option] -> IO ()
-runLlvmOpt logger dflags args = traceToolCommand logger "opt" $ do
+runLlvmOpt logger dflags args = traceSystoolCommand logger "opt" $ do
   let (p,args0) = pgm_lo dflags
       args1 = map Option (getOpts dflags opt_lo)
       -- We take care to pass -optlo flags (e.g. args0) last to ensure that the
@@ -194,7 +194,7 @@ runLlvmOpt logger dflags args = traceToolCommand logger "opt" $ do
 
 -- | Run the LLVM Compiler
 runLlvmLlc :: Logger -> DynFlags -> [Option] -> IO ()
-runLlvmLlc logger dflags args = traceToolCommand logger "llc" $ do
+runLlvmLlc logger dflags args = traceSystoolCommand logger "llc" $ do
   let (p,args0) = pgm_lc dflags
       args1 = map Option (getOpts dflags opt_lc)
   runSomething logger "LLVM Compiler" p (args0 ++ args1 ++ args)
@@ -203,7 +203,7 @@ runLlvmLlc logger dflags args = traceToolCommand logger "llc" $ do
 -- backend on OS X as LLVM doesn't support the OS X system
 -- assembler)
 runClang :: Logger -> DynFlags -> [Option] -> IO ()
-runClang logger dflags args = traceToolCommand logger "clang" $ do
+runClang logger dflags args = traceSystoolCommand logger "clang" $ do
   let (clang,_) = pgm_lcc dflags
       -- be careful what options we call clang with
       -- see #5903 and #7617 for bugs caused by this.
@@ -223,7 +223,7 @@ runClang logger dflags args = traceToolCommand logger "clang" $ do
 
 -- | Figure out which version of LLVM we are running this session
 figureLlvmVersion :: Logger -> DynFlags -> IO (Maybe LlvmVersion)
-figureLlvmVersion logger dflags = traceToolCommand logger "llc" $ do
+figureLlvmVersion logger dflags = traceSystoolCommand logger "llc" $ do
   let (pgm,opts) = pgm_lc dflags
       args = filter notNull (map showOpt opts)
       -- we grab the args even though they should be useless just in
@@ -266,7 +266,7 @@ figureLlvmVersion logger dflags = traceToolCommand logger "llc" $ do
 
 
 runLink :: Logger -> TmpFs -> DynFlags -> [Option] -> IO ()
-runLink logger tmpfs dflags args = traceToolCommand logger "linker" $ do
+runLink logger tmpfs dflags args = traceSystoolCommand logger "linker" $ do
   -- See Note [Run-time linker info]
   --
   -- `-optl` args come at the end, so that later `-l` options
@@ -331,7 +331,7 @@ ld: warning: symbol referencing errors
 -- See Note [Merging object files for GHCi] in GHC.Driver.Pipeline.
 runMergeObjects :: Logger -> TmpFs -> DynFlags -> [Option] -> IO ()
 runMergeObjects logger tmpfs dflags args =
-  traceToolCommand logger "merge-objects" $ do
+  traceSystoolCommand logger "merge-objects" $ do
     let (p,args0) = fromMaybe err (pgm_lm dflags)
         err = throwGhcException $ UsageError $ unwords
             [ "Attempted to merge object files but the configured linker"
@@ -348,7 +348,7 @@ runMergeObjects logger tmpfs dflags args =
         runSomething logger "Merge objects" p args2
 
 runAr :: Logger -> DynFlags -> Maybe FilePath -> [Option] -> IO ()
-runAr logger dflags cwd args = traceToolCommand logger "ar" $ do
+runAr logger dflags cwd args = traceSystoolCommand logger "ar" $ do
   let ar = pgm_ar dflags
   runSomethingFiltered logger id "Ar" ar args cwd Nothing
 
@@ -364,12 +364,12 @@ runInstallNameTool logger dflags args = do
   runSomethingFiltered logger id "Install Name Tool" tool args Nothing Nothing
 
 runRanlib :: Logger -> DynFlags -> [Option] -> IO ()
-runRanlib logger dflags args = traceToolCommand logger "ranlib" $ do
+runRanlib logger dflags args = traceSystoolCommand logger "ranlib" $ do
   let ranlib = pgm_ranlib dflags
   runSomethingFiltered logger id "Ranlib" ranlib args Nothing Nothing
 
 runWindres :: Logger -> DynFlags -> [Option] -> IO ()
-runWindres logger dflags args = traceToolCommand logger "windres" $ do
+runWindres logger dflags args = traceSystoolCommand logger "windres" $ do
   let cc_args = map Option (sOpt_c (settings dflags))
       windres = pgm_windres dflags
       opts = map Option (getOpts dflags opt_windres)
@@ -377,17 +377,5 @@ runWindres logger dflags args = traceToolCommand logger "windres" $ do
   runSomethingFiltered logger id "Windres" windres (opts ++ args) Nothing mb_env
 
 touch :: Logger -> DynFlags -> String -> String -> IO ()
-touch logger dflags purpose arg = traceToolCommand logger "touch" $
+touch logger dflags purpose arg = traceSystoolCommand logger "touch" $
   runSomething logger purpose (pgm_T dflags) [FileOption "" arg]
-
--- * Tracing utility
-
--- | Record in the eventlog when the given tool command starts
---   and finishes, prepending the given 'String' with
---   \"systool:\", to easily be able to collect and process
---   all the systool events.
---
---   For those events to show up in the eventlog, you need
---   to run GHC with @-v2@ or @-ddump-timings@.
-traceToolCommand :: Logger -> String -> IO a -> IO a
-traceToolCommand logger tool = withTiming logger (text "systool:" <> text tool) (const ())