Improvements to demand analysis

This patch collects a few improvements triggered by Trac #15696,
and fixing Trac #16029

* Stop making toCleanDmd behave specially for unlifted types.
  This special case was the cause of stupid behaviour in Trac
  #16029.  And to my joy I discovered the let/app invariant
  rendered it unnecessary.  (Maybe the special case pre-dated
  the let/app invariant.)

  Result: less special-case handling in the compiler, and
  better perf for the compiled code.

* In WwLib.mkWWstr_one, treat seqDmd like U(AAA).  It was not
  being so treated before, which again led to stupid code.

* Update and improve Notes

There are .stderr test wibbles because we get slightly different
strictness signatures for an argumment of unlifted type:
    <L,U> rather than <S,U>        for Int#
    <S,U> rather than <S(S),U(U)>  for Int

7 files changed, 38 insertions, 8 deletions

diff --git a/testsuite/tests/stranal/should_compile/Makefile b/testsuite/tests/stranal/should_compile/Makefile
index 16d1f2f84a..7ad39442bb 100644
--- a/testsuite/tests/stranal/should_compile/Makefile
+++ b/testsuite/tests/stranal/should_compile/Makefile
@@ -5,3 +5,8 @@ include $(TOP)/mk/test.mk
 T13031:
 	echo hello
 	'$(TEST_HC)' $(TEST_HC_OPTS) -c -fforce-recomp T13031.hs -ddump-simpl | grep 'Arity='
+
+# Trying to make sure the workers for g1 and g2
+# take only one Int# argument
+T16029:
+	'$(TEST_HC)' $(TEST_HC_OPTS) -c -O -fforce-recomp T16029.hs -dsuppress-uniques -ddump-simpl | grep '::.*Int'
diff --git a/testsuite/tests/stranal/should_compile/T16029.hs b/testsuite/tests/stranal/should_compile/T16029.hs
new file mode 100644
index 0000000000..b63414f59f
--- /dev/null
+++ b/testsuite/tests/stranal/should_compile/T16029.hs
@@ -0,0 +1,12 @@
+module T16029 where
+
+data S = MkS Int Int
+
+g1 :: S -> Int -> Int
+g1 (MkS x y) 0 = 0
+g1 (MkS x y) n = g1 (MkS y x) (n-1)
+
+data T = MkT !Int !Int
+g2 :: T -> Int -> Int
+g2 (MkT x y) 0 = 0
+g2 (MkT x y) n = g2 (MkT y x) (n-1)
diff --git a/testsuite/tests/stranal/should_compile/T16029.stdout b/testsuite/tests/stranal/should_compile/T16029.stdout
new file mode 100644
index 0000000000..c06ac7c8b3
--- /dev/null
+++ b/testsuite/tests/stranal/should_compile/T16029.stdout
@@ -0,0 +1,11 @@
+T16029.$WMkT [InlPrag=INLINE[2]] :: Int -> Int -> T
+         Tmpl= \ (dt [Occ=Once!] :: Int) (dt [Occ=Once!] :: Int) ->
+  = \ (dt [Occ=Once!] :: Int) (dt [Occ=Once!] :: Int) ->
+  :: GHC.Prim.Int# -> GHC.Prim.Int#
+  = \ (ww :: GHC.Prim.Int#) ->
+g2 [InlPrag=NOUSERINLINE[2]] :: T -> Int -> Int
+         Tmpl= \ (w [Occ=Once!] :: T) (w1 [Occ=Once!] :: Int) ->
+  = \ (w :: T) (w1 :: Int) ->
+g1 [InlPrag=NOUSERINLINE[2]] :: S -> Int -> Int
+         Tmpl= \ (w [Occ=Once!] :: S) (w1 [Occ=Once!] :: Int) ->
+  = \ (w :: S) (w1 :: Int) ->
diff --git a/testsuite/tests/stranal/should_compile/all.T b/testsuite/tests/stranal/should_compile/all.T
index a2aa1d51a9..38c15f2b30 100644
--- a/testsuite/tests/stranal/should_compile/all.T
+++ b/testsuite/tests/stranal/should_compile/all.T
@@ -47,3 +47,5 @@ test('T13077a', normal, compile, [''])
 #   The idea is to check that both $wmutVar and $warray
 #   don't mention MutVar# and Array# anymore.
 test('T15627',  [ grep_errmsg(r'(wmutVar|warray).*Int#') ], compile, ['-dppr-cols=200 -ddump-simpl'])
+
+test('T16029', normal, run_command, ['$MAKE -s --no-print-directory T16029'])
diff --git a/testsuite/tests/stranal/sigs/HyperStrUse.stderr b/testsuite/tests/stranal/sigs/HyperStrUse.stderr
index 21077d243f..84d81f3a8b 100644
--- a/testsuite/tests/stranal/sigs/HyperStrUse.stderr
+++ b/testsuite/tests/stranal/sigs/HyperStrUse.stderr
@@ -1,12 +1,12 @@
 
 ==================== Strictness signatures ====================
 HyperStrUse.$trModule: m
-HyperStrUse.f: <S(S(S)L),1*U(1*U(U),A)><S,1*U>m
+HyperStrUse.f: <S(SL),1*U(1*U(U),A)><S,1*U>m
 
 
 
 ==================== Strictness signatures ====================
 HyperStrUse.$trModule: m
-HyperStrUse.f: <S(S(S)L),1*U(1*U(U),A)><S,1*U>m
+HyperStrUse.f: <S(SL),1*U(1*U(U),A)><S,1*U>m
 
 
diff --git a/testsuite/tests/stranal/sigs/T12370.stderr b/testsuite/tests/stranal/sigs/T12370.stderr
index f8cb839436..d1acdf0b50 100644
--- a/testsuite/tests/stranal/sigs/T12370.stderr
+++ b/testsuite/tests/stranal/sigs/T12370.stderr
@@ -1,14 +1,14 @@
 
 ==================== Strictness signatures ====================
 T12370.$trModule: m
-T12370.bar: <S(S),1*U(U)><S(S),1*U(U)>m
-T12370.foo: <S(S(S)S(S)),1*U(1*U(U),1*U(U))>m
+T12370.bar: <S,1*U(U)><S,1*U(U)>m
+T12370.foo: <S(SS),1*U(1*U(U),1*U(U))>m
 
 
 
 ==================== Strictness signatures ====================
 T12370.$trModule: m
-T12370.bar: <S(S),1*U(U)><S(S),1*U(U)>m
-T12370.foo: <S(S(S)S(S)),1*U(1*U(U),1*U(U))>m
+T12370.bar: <S,1*U(U)><S,1*U(U)>m
+T12370.foo: <S(SS),1*U(1*U(U),1*U(U))>m
 
 
diff --git a/testsuite/tests/stranal/sigs/T8598.stderr b/testsuite/tests/stranal/sigs/T8598.stderr
index c084e15a99..9bf10d94f4 100644
--- a/testsuite/tests/stranal/sigs/T8598.stderr
+++ b/testsuite/tests/stranal/sigs/T8598.stderr
@@ -1,12 +1,12 @@
 
 ==================== Strictness signatures ====================
 T8598.$trModule: m
-T8598.fun: <S(S),1*U(U)>m
+T8598.fun: <S,1*U(U)>m
 
 
 
 ==================== Strictness signatures ====================
 T8598.$trModule: m
-T8598.fun: <S(S),1*U(U)>m
+T8598.fun: <S,1*U(U)>m