Fix -ddump-stg flag

-ddump-stg was dumping the initial STG (just after Core-to-STG pass)
which was misleading because we want the final STG to know if a function
allocates or not. Now we have a new flag -ddump-stg-from-core for this and
-ddump-stg is deprecated.

6 files changed, 20 insertions, 9 deletions

diff --git a/compiler/GHC/Driver/Flags.hs b/compiler/GHC/Driver/Flags.hs
index a1691c1397..9f9e9edbab 100644
--- a/compiler/GHC/Driver/Flags.hs
+++ b/compiler/GHC/Driver/Flags.hs
@@ -68,9 +68,9 @@ data DumpFlag
    | Opt_D_dump_simpl_iterations
    | Opt_D_dump_spec
    | Opt_D_dump_prep
-   | Opt_D_dump_stg -- CoreToStg output
-   | Opt_D_dump_stg_unarised -- STG after unarise
-   | Opt_D_dump_stg_final -- STG after stg2stg
+   | Opt_D_dump_stg_from_core -- ^ Initial STG (CoreToStg output)
+   | Opt_D_dump_stg_unarised  -- ^ STG after unarise
+   | Opt_D_dump_stg_final     -- ^ Final STG (after stg2stg)
    | Opt_D_dump_call_arity
    | Opt_D_dump_exitify
    | Opt_D_dump_stranal
diff --git a/compiler/GHC/Driver/Session.hs b/compiler/GHC/Driver/Session.hs
index 40ccb400bc..b5ded38737 100644
--- a/compiler/GHC/Driver/Session.hs
+++ b/compiler/GHC/Driver/Session.hs
@@ -2586,12 +2586,15 @@ dynamic_flags_deps = [
         (setDumpFlag Opt_D_dump_spec)
   , make_ord_flag defGhcFlag "ddump-prep"
         (setDumpFlag Opt_D_dump_prep)
-  , make_ord_flag defGhcFlag "ddump-stg"
-        (setDumpFlag Opt_D_dump_stg)
+  , make_ord_flag defGhcFlag "ddump-stg-from-core"
+        (setDumpFlag Opt_D_dump_stg_from_core)
   , make_ord_flag defGhcFlag "ddump-stg-unarised"
         (setDumpFlag Opt_D_dump_stg_unarised)
   , make_ord_flag defGhcFlag "ddump-stg-final"
         (setDumpFlag Opt_D_dump_stg_final)
+  , make_dep_flag defGhcFlag "ddump-stg"
+        (setDumpFlag Opt_D_dump_stg_from_core)
+        "Use `-ddump-stg-from-core` or `-ddump-stg-final` instead"
   , make_ord_flag defGhcFlag "ddump-call-arity"
         (setDumpFlag Opt_D_dump_call_arity)
   , make_ord_flag defGhcFlag "ddump-exitify"
diff --git a/compiler/GHC/Stg/Pipeline.hs b/compiler/GHC/Stg/Pipeline.hs
index 3891346dab..ea758e58db 100644
--- a/compiler/GHC/Stg/Pipeline.hs
+++ b/compiler/GHC/Stg/Pipeline.hs
@@ -52,7 +52,7 @@ stg2stg :: DynFlags                  -- includes spec of what stg-to-stg passes
         -> IO [StgTopBinding]        -- output program
 
 stg2stg dflags this_mod binds
-  = do  { dump_when Opt_D_dump_stg "STG:" binds
+  = do  { dump_when Opt_D_dump_stg_from_core "Initial STG:" binds
         ; showPass dflags "Stg2Stg"
         -- Do the main business!
         ; binds' <- runStgM 'g' $
diff --git a/docs/users_guide/debugging.rst b/docs/users_guide/debugging.rst
index 4b86617093..75728ae7d7 100644
--- a/docs/users_guide/debugging.rst
+++ b/docs/users_guide/debugging.rst
@@ -387,7 +387,7 @@ STG representation
 
 These flags dump various phases of GHC's STG pipeline.
 
-.. ghc-flag:: -ddump-stg
+.. ghc-flag:: -ddump-stg-from-core
     :shortdesc: Show CoreToStg output
     :type: dynamic
 
@@ -411,6 +411,14 @@ These flags dump various phases of GHC's STG pipeline.
 
     Show the output of the last STG pass before we generate Cmm.
 
+.. ghc-flag:: -ddump-stg
+    :shortdesc: *(deprecated)* Alias for :ghc-flag:`-ddump-stg-from-core`
+    :type: dynamic
+
+    Alias for :ghc-flag:`-ddump-stg-from-core`. Deprecated in favor of more explicit
+    flags: :ghc-flag:`-ddump-stg-from-core`, :ghc-flag:`-ddump-stg-final`, etc.
+
+
 C-\\- representation
 ~~~~~~~~~~~~~~~~~~~~
 
diff --git a/testsuite/tests/simplCore/should_compile/all.T b/testsuite/tests/simplCore/should_compile/all.T
index 0abd79858b..c033150957 100644
--- a/testsuite/tests/simplCore/should_compile/all.T
+++ b/testsuite/tests/simplCore/should_compile/all.T
@@ -210,7 +210,7 @@ test('T12076lit', normal, compile, ['-O'])
 test('T12076sat', normal, compile, ['-O'])
 test('T12212', normal, compile, ['-O'])
 
-test('noinline01', only_ways(['optasm']), compile, ['-ddump-stg -dsuppress-uniques -dsuppress-ticks -O'])
+test('noinline01', only_ways(['optasm']), compile, ['-ddump-stg-from-core -dsuppress-uniques -dsuppress-ticks -O'])
 test('par01', only_ways(['optasm']), compile, ['-ddump-prep -dsuppress-uniques -dsuppress-ticks -O2'])
 test('T12776', normal, compile, ['-O2'])
 test('T9509',
diff --git a/testsuite/tests/simplCore/should_compile/noinline01.stderr b/testsuite/tests/simplCore/should_compile/noinline01.stderr
index f8b6cbb30f..d38b5dee03 100644
--- a/testsuite/tests/simplCore/should_compile/noinline01.stderr
+++ b/testsuite/tests/simplCore/should_compile/noinline01.stderr
@@ -1,5 +1,5 @@
 
-==================== STG: ====================
+==================== Initial STG: ====================
 Noinline01.f [InlPrag=INLINE (sat-args=1)]
   :: forall {p}. p -> GHC.Types.Bool
 [GblId, Arity=1, Str=<L,A>, Unf=OtherCon []] =