Remove ad-hoc special case in occAnal

Back in 1999 I put this ad-hoc code in the Case-handling
code for occAnal:

  occAnal env (Case scrut bndr ty alts)
   = ...
        -- Note [Case binder usage]
        -- ~~~~~~~~~~~~~~~~~~~~~~~~
        -- The case binder gets a usage of either "many" or "dead", never "one".
        -- Reason: we like to inline single occurrences, to eliminate a binding,
        -- but inlining a case binder *doesn't* eliminate a binding.
        -- We *don't* want to transform
        --      case x of w { (p,q) -> f w }
        -- into
        --      case x of w { (p,q) -> f (p,q) }
    tag_case_bndr usage bndr
      = (usage', setIdOccInfo bndr final_occ_info)
      where
        occ_info       = lookupDetails usage bndr
        usage'         = usage `delDetails` bndr
        final_occ_info = case occ_info of IAmDead -> IAmDead
                                          _       -> noOccInfo

But the comment looks wrong -- the bad inlining will not happen -- and
I think it relates to some long-ago version of the simplifier.

So I simply removed the special case, which gives more accurate
occurrence-info to the case binder.  Interestingly I got a slight
improvement in nofib binary sizes.

--------------------------------------------------------------------------------
        Program           Size    Allocs   Runtime   Elapsed  TotalMem
--------------------------------------------------------------------------------
      cacheprof          -0.1%     +0.2%     -0.7%     -1.2%     +8.6%
--------------------------------------------------------------------------------
            Min          -0.2%      0.0%    -14.5%    -30.5%      0.0%
            Max          -0.1%     +0.2%    +10.0%    +10.0%    +25.0%
 Geometric Mean          -0.2%     +0.0%     -1.9%     -5.4%     +0.3%

I have no idea if the improvement in runtime is real.  I did look at the
tiny increase in allocation for cacheprof and concluded that it was
unimportant (I forget the details).

Also the more accurate occ-info for the case binder meant that some
inlining happens in one pass that previously took successive passes
for the test dependent/should_compile/dynamic-paper (which has a
known Russel-paradox infinite loop in the simplifier).

In short, a small win: less ad-hoc complexity and slightly smaller
binaries.

9 files changed, 19 insertions, 10 deletions

diff --git a/testsuite/tests/codeGen/should_compile/T14626.stdout b/testsuite/tests/codeGen/should_compile/T14626.stdout
index 31e280e062..389d3e733a 100644
--- a/testsuite/tests/codeGen/should_compile/T14626.stdout
+++ b/testsuite/tests/codeGen/should_compile/T14626.stdout
@@ -1,2 +1,2 @@
-      case dt of dt { __DEFAULT -> T14626.MkT dt }
+      case dt of dt [Occ=Once] { __DEFAULT -> T14626.MkT dt }
       case v of { T14626.MkT y [Occ=Once] ->
diff --git a/testsuite/tests/dependent/should_compile/all.T b/testsuite/tests/dependent/should_compile/all.T
index 66221840bb..e153cafe41 100644
--- a/testsuite/tests/dependent/should_compile/all.T
+++ b/testsuite/tests/dependent/should_compile/all.T
@@ -17,7 +17,7 @@ test('T9632', normal, compile, [''])
 # discussed in #11330.
 test('dynamic-paper',
      expect_broken_for(11330, ['profasm']),
-     compile, [''])
+     compile_fail, [''])
 test('T11311', normal, compile, [''])
 test('T11405', normal, compile, [''])
 test('T11241', normal, compile, [''])
diff --git a/testsuite/tests/dependent/should_compile/dynamic-paper.stderr b/testsuite/tests/dependent/should_compile/dynamic-paper.stderr
new file mode 100644
index 0000000000..0519ecba6e
--- /dev/null
+++ b/testsuite/tests/dependent/should_compile/dynamic-paper.stderr
@@ -0,0 +1 @@
+ 
\ No newline at end of file
diff --git a/testsuite/tests/simplCore/should_compile/T13143.stderr b/testsuite/tests/simplCore/should_compile/T13143.stderr
index 160a4a2c93..d8b0c1b468 100644
--- a/testsuite/tests/simplCore/should_compile/T13143.stderr
+++ b/testsuite/tests/simplCore/should_compile/T13143.stderr
@@ -105,7 +105,9 @@ g [InlPrag=NOUSERINLINE[2]] :: Bool -> Bool -> Int -> Int
                  (w1 [Occ=Once] :: Bool)
                  (w2 [Occ=Once!] :: Int) ->
                  case w2 of { GHC.Types.I# ww1 [Occ=Once] ->
-                 case T13143.$wg w w1 ww1 of ww2 { __DEFAULT -> GHC.Types.I# ww2 }
+                 case T13143.$wg w w1 ww1 of ww2 [Occ=Once] { __DEFAULT ->
+                 GHC.Types.I# ww2
+                 }
                  }}]
 g = \ (w :: Bool) (w1 :: Bool) (w2 :: Int) ->
       case w2 of { GHC.Types.I# ww1 ->
diff --git a/testsuite/tests/simplCore/should_compile/T3717.stderr b/testsuite/tests/simplCore/should_compile/T3717.stderr
index a271850abf..45fdf89bb4 100644
--- a/testsuite/tests/simplCore/should_compile/T3717.stderr
+++ b/testsuite/tests/simplCore/should_compile/T3717.stderr
@@ -71,7 +71,9 @@ foo [InlPrag=NOUSERINLINE[2]] :: Int -> Int
          Guidance=ALWAYS_IF(arity=1,unsat_ok=True,boring_ok=False)
          Tmpl= \ (w [Occ=Once!] :: Int) ->
                  case w of { GHC.Types.I# ww1 [Occ=Once] ->
-                 case T3717.$wfoo ww1 of ww2 { __DEFAULT -> GHC.Types.I# ww2 }
+                 case T3717.$wfoo ww1 of ww2 [Occ=Once] { __DEFAULT ->
+                 GHC.Types.I# ww2
+                 }
                  }}]
 foo
   = \ (w :: Int) ->
diff --git a/testsuite/tests/simplCore/should_compile/T4930.stderr b/testsuite/tests/simplCore/should_compile/T4930.stderr
index 02e8a6c65e..7556ecc9af 100644
--- a/testsuite/tests/simplCore/should_compile/T4930.stderr
+++ b/testsuite/tests/simplCore/should_compile/T4930.stderr
@@ -71,7 +71,9 @@ foo [InlPrag=NOUSERINLINE[2]] :: Int -> Int
          Guidance=ALWAYS_IF(arity=1,unsat_ok=True,boring_ok=False)
          Tmpl= \ (w [Occ=Once!] :: Int) ->
                  case w of { GHC.Types.I# ww1 [Occ=Once] ->
-                 case T4930.$wfoo ww1 of ww2 { __DEFAULT -> GHC.Types.I# ww2 }
+                 case T4930.$wfoo ww1 of ww2 [Occ=Once] { __DEFAULT ->
+                 GHC.Types.I# ww2
+                 }
                  }}]
 foo
   = \ (w :: Int) ->
diff --git a/testsuite/tests/simplCore/should_compile/T7360.stderr b/testsuite/tests/simplCore/should_compile/T7360.stderr
index 8ae5953b43..f310e8f7a8 100644
--- a/testsuite/tests/simplCore/should_compile/T7360.stderr
+++ b/testsuite/tests/simplCore/should_compile/T7360.stderr
@@ -57,10 +57,10 @@ fun2 :: forall a. [a] -> ((), Int)
          Guidance=ALWAYS_IF(arity=1,unsat_ok=True,boring_ok=False)
          Tmpl= \ (@ a) (x [Occ=Once!] :: [a]) ->
                  (T7360.fun5,
-                  case x of wild {
+                  case x of wild [Occ=Once] {
                     [] -> T7360.fun4;
                     : _ [Occ=Dead] _ [Occ=Dead] ->
-                      case GHC.List.$wlenAcc @ a wild 0# of ww2 { __DEFAULT ->
+                      case GHC.List.$wlenAcc @ a wild 0# of ww2 [Occ=Once] { __DEFAULT ->
                       GHC.Types.I# ww2
                       }
                   })}]
diff --git a/testsuite/tests/simplCore/should_compile/T7865.stdout b/testsuite/tests/simplCore/should_compile/T7865.stdout
index 7ea5449fbe..4073fec7ad 100644
--- a/testsuite/tests/simplCore/should_compile/T7865.stdout
+++ b/testsuite/tests/simplCore/should_compile/T7865.stdout
@@ -1,7 +1,7 @@
 T7865.$wexpensive [InlPrag=NOINLINE]
 T7865.$wexpensive
 expensive [InlPrag=NOUSERINLINE[0]] :: Int -> Int
-                 case T7865.$wexpensive ww1 of ww2 { __DEFAULT -> GHC.Types.I# ww2 }
+                 case T7865.$wexpensive ww1 of ww2 [Occ=Once] { __DEFAULT ->
 expensive
       case T7865.$wexpensive ww1 of ww2 { __DEFAULT -> GHC.Types.I# ww2 }
             case T7865.$wexpensive ww1 of ww2 { __DEFAULT ->
diff --git a/testsuite/tests/simplCore/should_compile/spec-inline.stderr b/testsuite/tests/simplCore/should_compile/spec-inline.stderr
index 0b0c79695a..65dd9a1aa0 100644
--- a/testsuite/tests/simplCore/should_compile/spec-inline.stderr
+++ b/testsuite/tests/simplCore/should_compile/spec-inline.stderr
@@ -144,7 +144,9 @@ Roman.foo_go [InlPrag=NOUSERINLINE[2]]
          WorkFree=True, Expandable=True,
          Guidance=ALWAYS_IF(arity=2,unsat_ok=True,boring_ok=False)
          Tmpl= \ (w [Occ=Once] :: Maybe Int) (w1 [Occ=Once] :: Maybe Int) ->
-                 case Roman.$wgo w w1 of ww { __DEFAULT -> GHC.Types.I# ww }}]
+                 case Roman.$wgo w w1 of ww [Occ=Once] { __DEFAULT ->
+                 GHC.Types.I# ww
+                 }}]
 Roman.foo_go
   = \ (w :: Maybe Int) (w1 :: Maybe Int) ->
       case Roman.$wgo w w1 of ww { __DEFAULT -> GHC.Types.I# ww }
@@ -177,7 +179,7 @@ foo :: Int -> Int
          WorkFree=True, Expandable=True,
          Guidance=ALWAYS_IF(arity=1,unsat_ok=True,boring_ok=False)
          Tmpl= \ (n [Occ=Once!] :: Int) ->
-                 case n of n1 { GHC.Types.I# _ [Occ=Dead] ->
+                 case n of n1 [Occ=Once] { GHC.Types.I# _ [Occ=Dead] ->
                  Roman.foo_go (GHC.Base.Just @ Int n1) Roman.foo1
                  }}]
 foo