Dump non-module specific info to file #20316

- Change the dumpPrefix to FilePath, and default to non-module
- Add dot to seperate dump-file-prefix and suffix
- Modify user guide to introduce how dump files are named
- This commit does not affect Ghci dump file naming.

See also #17500

9 files changed, 41 insertions, 21 deletions

diff --git a/compiler/GHC/Driver/Pipeline.hs b/compiler/GHC/Driver/Pipeline.hs
index c758202268..8645184b1f 100644
--- a/compiler/GHC/Driver/Pipeline.hs
+++ b/compiler/GHC/Driver/Pipeline.hs
@@ -634,7 +634,7 @@ mkPipeEnv stop_phase  input_fn output =
 
 setDumpPrefix :: PipeEnv -> HscEnv -> HscEnv
 setDumpPrefix pipe_env hsc_env =
-  hscUpdateFlags (\dflags -> dflags { dumpPrefix = Just (src_basename pipe_env ++ ".")}) hsc_env
+  hscUpdateFlags (\dflags -> dflags { dumpPrefix = src_basename pipe_env ++ "."}) hsc_env
 
 {- The Pipelines -}
 
diff --git a/compiler/GHC/Driver/Session.hs b/compiler/GHC/Driver/Session.hs
index ccf4d18f2f..f7d24d1fd5 100644
--- a/compiler/GHC/Driver/Session.hs
+++ b/compiler/GHC/Driver/Session.hs
@@ -549,9 +549,10 @@ data DynFlags = DynFlags {
                                   -- used to query the appropriate fields
                                   -- (outputFile/dynOutputFile, ways, etc.)
 
-  -- | This is set by 'GHC.Driver.Pipeline.setDumpPrefix'
-  --    or 'ghc.GHCi.UI.runStmt' based on where its output is going.
-  dumpPrefix            :: Maybe FilePath,
+  -- | This defaults to 'non-module'. It can be set by
+  -- 'GHC.Driver.Pipeline.setDumpPrefix' or 'ghc.GHCi.UI.runStmt' based on
+  -- where its output is going.
+  dumpPrefix            :: FilePath,
 
   -- | Override the 'dumpPrefix' set by 'GHC.Driver.Pipeline.setDumpPrefix'
   --    or 'ghc.GHCi.UI.runStmt'.
@@ -1159,7 +1160,7 @@ defaultDynFlags mySettings llvmConfig =
         outputHi                = Nothing,
         dynOutputHi             = Nothing,
         dynLibLoader            = SystemDependent,
-        dumpPrefix              = Nothing,
+        dumpPrefix              = "non-module.",
         dumpPrefixForce         = Nothing,
         ldInputs                = [],
         includePaths            = IncludeSpecs [] [] [],
@@ -2192,7 +2193,7 @@ dynamic_flags_deps = [
   , make_ord_flag defGhcFlag "dumpdir"           (hasArg setDumpDir)
   , make_ord_flag defGhcFlag "outputdir"         (hasArg setOutputDir)
   , make_ord_flag defGhcFlag "ddump-file-prefix"
-        (hasArg (setDumpPrefixForce . Just))
+        (hasArg (setDumpPrefixForce . Just . flip (++) "."))
 
   , make_ord_flag defGhcFlag "dynamic-too"
         (NoArg (setGeneralFlag Opt_BuildDynamicToo))
diff --git a/compiler/GHC/Utils/Logger.hs b/compiler/GHC/Utils/Logger.hs
index 48601dd655..5593425b53 100644
--- a/compiler/GHC/Utils/Logger.hs
+++ b/compiler/GHC/Utils/Logger.hs
@@ -116,7 +116,7 @@ data LogFlags = LogFlags
   , log_enable_timestamps    :: !Bool               -- ^ Enable timestamps
   , log_dump_to_file         :: !Bool               -- ^ Enable dump to file
   , log_dump_dir             :: !(Maybe FilePath)   -- ^ Dump directory
-  , log_dump_prefix          :: !(Maybe FilePath)   -- ^ Normal dump path ("basename.")
+  , log_dump_prefix          :: !FilePath           -- ^ Normal dump path ("basename.")
   , log_dump_prefix_override :: !(Maybe FilePath)   -- ^ Overriden dump path
   , log_enable_debug         :: !Bool               -- ^ Enable debug output
   , log_verbosity            :: !Int                -- ^ Verbosity level
@@ -133,7 +133,7 @@ defaultLogFlags = LogFlags
   , log_enable_timestamps    = True
   , log_dump_to_file         = False
   , log_dump_dir             = Nothing
-  , log_dump_prefix          = Nothing
+  , log_dump_prefix          = ""
   , log_dump_prefix_override = Nothing
   , log_enable_debug         = False
   , log_verbosity            = 0
@@ -485,8 +485,7 @@ withDumpFileHandle dumps logflags flag action = do
 chooseDumpFile :: LogFlags -> DumpFlag -> Maybe FilePath
 chooseDumpFile logflags flag
     | log_dump_to_file logflags || forced_to_file
-    , Just prefix <- getPrefix
-    = Just $ setDir (prefix ++ dump_suffix)
+    = Just $ setDir (getPrefix ++ dump_suffix)
 
     | otherwise
     = Nothing
@@ -510,13 +509,12 @@ chooseDumpFile logflags flag
          -- dump file location is being forced
          --      by the --ddump-file-prefix flag.
        | Just prefix <- log_dump_prefix_override logflags
-          = Just prefix
-         -- dump file location chosen by GHC.Driver.Pipeline.runPipeline
-       | Just prefix <- log_dump_prefix logflags
-          = Just prefix
-         -- we haven't got a place to put a dump file.
+          = prefix
+         -- dump file locations, module specified to [modulename] set by
+         -- GHC.Driver.Pipeline.runPipeline; non-module specific, e.g. Chasing dependencies,
+         -- to 'non-module' by default.
        | otherwise
-          = Nothing
+          = log_dump_prefix logflags
     setDir f = case log_dump_dir logflags of
                  Just d  -> d </> f
                  Nothing ->       f
diff --git a/docs/users_guide/debugging.rst b/docs/users_guide/debugging.rst
index ec40a5e251..569923ade4 100644
--- a/docs/users_guide/debugging.rst
+++ b/docs/users_guide/debugging.rst
@@ -27,10 +27,14 @@ Dumping out compiler intermediate structures
     :shortdesc: Dump to files instead of stdout
     :type: dynamic
 
-    Causes the output from all of the flags listed below to be dumped
-    to a file. The file name depends upon the output produced; for instance,
-    output from :ghc-flag:`-ddump-simpl` will end up in
-    :file:`{module}.dump-simpl`.
+    Causes the output from each of flags starting with "-ddump", to be
+    dumped to a file or files. If you want to have all the output from one
+    single flag saved to one file, use :ghc-flag:`-ddump-file-prefix=⟨str⟩`
+    (see descriptions below). Otherwise, the output will go to several
+    files, including one for non-module specific and several for module
+    specific. The suffix of a dump file depends on the flag turned on, for
+    instance, output from :ghc-flag:`-ddump-simpl` will end up in
+    :file:`prefix.dump-simpl`.
 
 .. ghc-flag:: -ddump-file-prefix=⟨str⟩
     :shortdesc: Set the prefix of the filenames used for debugging output.
diff --git a/ghc/GHCi/UI.hs b/ghc/GHCi/UI.hs
index b628575362..3a7946bca8 100644
--- a/ghc/GHCi/UI.hs
+++ b/ghc/GHCi/UI.hs
@@ -1299,7 +1299,7 @@ runStmt input step = do
     setDumpFilePrefix :: GHC.GhcMonad m => InteractiveContext -> m () -- #17500
     setDumpFilePrefix ic = do
         dflags <- GHC.getInteractiveDynFlags
-        GHC.setInteractiveDynFlags dflags { dumpPrefix = Just (modStr ++ ".") }
+        GHC.setInteractiveDynFlags dflags { dumpPrefix = modStr ++ "." }
       where
         modStr = moduleNameString $ moduleName $ icInteractiveModule $ ic
 
diff --git a/testsuite/tests/driver/Makefile b/testsuite/tests/driver/Makefile
index 58d35b5a06..0542f9de47 100644
--- a/testsuite/tests/driver/Makefile
+++ b/testsuite/tests/driver/Makefile
@@ -733,3 +733,9 @@ T20084:
 	# Don't compile
 	"$(TEST_HC)" $(TEST_HC_OPTS) T20084.hs
 
+.PHONY: T20316
+T20316:
+	echo 'main = print "Hello World"' > T20316.hs
+	"$(TEST_HC)" $(TEST_HC_OPTS) -fno-code T20316.hs -ddump-to-file -ddump-timings;
+	echo "*** non-module.dump-timings ***"
+	cat non-module.dump-timings | grep alloc | sed 's/alloc.*//'
diff --git a/testsuite/tests/driver/T20316.stderr b/testsuite/tests/driver/T20316.stderr
new file mode 100644
index 0000000000..ef979dec18
--- /dev/null
+++ b/testsuite/tests/driver/T20316.stderr
@@ -0,0 +1,6 @@
+*** initializing unit database:
+*** Chasing dependencies:
+*** Parser [Main]:
+*** Renamer/typechecker [Main]:
+*** Desugar [Main]:
+*** CoreTidy [Main]:
diff --git a/testsuite/tests/driver/T20316.stdout b/testsuite/tests/driver/T20316.stdout
new file mode 100644
index 0000000000..280a3c80e7
--- /dev/null
+++ b/testsuite/tests/driver/T20316.stdout
@@ -0,0 +1,4 @@
+[1 of 1] Compiling Main             ( T20316.hs, nothing )
+*** non-module.dump-timings ***
+initializing unit database: 
+Chasing dependencies: 
diff --git a/testsuite/tests/driver/all.T b/testsuite/tests/driver/all.T
index 742f74f953..4af15b7640 100644
--- a/testsuite/tests/driver/all.T
+++ b/testsuite/tests/driver/all.T
@@ -301,3 +301,4 @@ test('T20459', normal, multimod_compile_fail,
      ['T20459B', ''])
 test('T20200loop', extra_files(['T20200loop']), multimod_compile,
      ['Datatypes', '-iT20200loop -O -v0'])
+test('T20316', normal, makefile_test, [])