Tweak Cmm dumps to avoid generating sections for empty groups

When dumping Cmm groups check if the group is empty, to avoid generating
empty sections in dump files like

    ==================== Output Cmm ====================
    []

Also fixes a few bad indentation in the code around changes.

1 files changed, 20 insertions, 15 deletions

diff --git a/compiler/main/HscMain.hs b/compiler/main/HscMain.hs
index 016cad9..7d99c46 100644
--- a/compiler/main/HscMain.hs
+++ b/compiler/main/HscMain.hs
@@ -1456,9 +1456,10 @@ hscGenHardCode hsc_env cgguts location output_filename = do
             rawcmms0 <- {-# SCC "cmmToRawCmm" #-}
                       cmmToRawCmm dflags cmms
 
-            let dump a = do dumpIfSet_dyn dflags Opt_D_dump_cmm_raw "Raw Cmm"
-                              FormatCMM (ppr a)
-                            return a
+            let dump a = do
+                  unless (null a) $
+                    dumpIfSet_dyn dflags Opt_D_dump_cmm_raw "Raw Cmm" FormatCMM (ppr a)
+                  return a
                 rawcmms1 = Stream.mapM dump rawcmms0
 
             (output_filename, (_stub_h_exists, stub_c_exists), foreign_fps, ())
@@ -1512,8 +1513,9 @@ hscCompileCmmFile hsc_env filename output_filename = runHsc hsc_env $ do
             mod_name = mkModuleName $ "Cmm$" ++ FilePath.takeFileName filename
             cmm_mod = mkModule (thisPackage dflags) mod_name
         (_, cmmgroup) <- cmmPipeline hsc_env (emptySRT cmm_mod) cmm
-        dumpIfSet_dyn dflags Opt_D_dump_cmm "Output Cmm"
-          FormatCMM (ppr cmmgroup)
+        unless (null cmmgroup) $
+          dumpIfSet_dyn dflags Opt_D_dump_cmm "Output Cmm"
+            FormatCMM (ppr cmmgroup)
         rawCmms <- cmmToRawCmm dflags (Stream.yield cmmgroup)
         _ <- codeOutput dflags cmm_mod output_filename no_loc NoStubs [] []
              rawCmms
@@ -1550,20 +1552,23 @@ doCodeGen hsc_env this_mod data_tycons
         -- CmmGroup on input may produce many CmmGroups on output due
         -- to proc-point splitting).
 
-    let dump1 a = do dumpIfSet_dyn dflags Opt_D_dump_cmm_from_stg
-                       "Cmm produced by codegen" FormatCMM (ppr a)
-                     return a
+    let dump1 a = do
+          unless (null a) $
+            dumpIfSet_dyn dflags Opt_D_dump_cmm_from_stg
+              "Cmm produced by codegen" FormatCMM (ppr a)
+          return a
 
         ppr_stream1 = Stream.mapM dump1 cmm_stream
 
-        pipeline_stream
-           = {-# SCC "cmmPipeline" #-}
-             let run_pipeline = cmmPipeline hsc_env
-             in void $ Stream.mapAccumL run_pipeline (emptySRT this_mod) ppr_stream1
+        pipeline_stream =
+          {-# SCC "cmmPipeline" #-}
+          let run_pipeline = cmmPipeline hsc_env
+          in void $ Stream.mapAccumL run_pipeline (emptySRT this_mod) ppr_stream1
 
-        dump2 a = do dumpIfSet_dyn dflags Opt_D_dump_cmm
-                        "Output Cmm" FormatCMM (ppr a)
-                     return a
+        dump2 a = do
+          unless (null a) $
+            dumpIfSet_dyn dflags Opt_D_dump_cmm "Output Cmm" FormatCMM (ppr a)
+          return a
 
         ppr_stream2 = Stream.mapM dump2 pipeline_stream