CprAnal: Don't attach CPR sigs to expandable bindings (#18154)

Instead, look through expandable unfoldings in `cprTransform`.
See the new Note [CPR for expandable unfoldings]:

```
Long static data structures (whether top-level or not) like

  xs = x1 : xs1
  xs1 = x2 : xs2
  xs2 = x3 : xs3

should not get CPR signatures, because they

  * Never get WW'd, so their CPR signature should be irrelevant after analysis
    (in fact the signature might even be harmful for that reason)
  * Would need to be inlined/expanded to see their constructed product
  * Recording CPR on them blows up interface file sizes and is redundant with
    their unfolding. In case of Nested CPR, this blow-up can be quadratic!

But we can't just stop giving DataCon application bindings the CPR property,
for example

  fac 0 = 1
  fac n = n * fac (n-1)

fac certainly has the CPR property and should be WW'd! But FloatOut will
transform the first clause to

  lvl = 1
  fac 0 = lvl

If lvl doesn't have the CPR property, fac won't either. But lvl doesn't have a
CPR signature to extrapolate into a CPR transformer ('cprTransform'). So
instead we keep on cprAnal'ing through *expandable* unfoldings for these arity
0 bindings via 'cprExpandUnfolding_maybe'.

In practice, GHC generates a lot of (nested) TyCon and KindRep bindings, one
for each data declaration. It's wasteful to attach CPR signatures to each of
them (and intractable in case of Nested CPR).
```

Fixes #18154.

14 files changed, 54 insertions, 58 deletions

diff --git a/testsuite/tests/stranal/should_compile/T10694.stderr b/testsuite/tests/stranal/should_compile/T10694.stderr
index 66a337ab24..ee700fc6c6 100644
--- a/testsuite/tests/stranal/should_compile/T10694.stderr
+++ b/testsuite/tests/stranal/should_compile/T10694.stderr
@@ -6,26 +6,26 @@ Result size of Tidy Core = {terms: 74, types: 65, coercions: 0, joins: 0/4}
 T10694.$wpm [InlPrag=NOINLINE] :: Int -> Int -> (# Int, Int #)
 [GblId, Arity=2, Str=<L,U(U)><L,U(U)>, Unf=OtherCon []]
 T10694.$wpm
-  = \ (w_s1vj :: Int) (w1_s1vk :: Int) ->
+  = \ (w_s1v1 :: Int) (w1_s1v2 :: Int) ->
       let {
-        l_s1uR :: Int
+        l_s1uz :: Int
         [LclId]
-        l_s1uR
-          = case w_s1vj of { GHC.Types.I# x_aJ9 -> case w1_s1vk of { GHC.Types.I# y_aJc -> GHC.Types.I# (GHC.Prim.+# x_aJ9 y_aJc) } } } in
+        l_s1uz
+          = case w_s1v1 of { GHC.Types.I# x_aJ0 -> case w1_s1v2 of { GHC.Types.I# y_aJ3 -> GHC.Types.I# (GHC.Prim.+# x_aJ0 y_aJ3) } } } in
       let {
-        l1_s1uS :: Int
+        l1_s1uA :: Int
         [LclId]
-        l1_s1uS
-          = case w_s1vj of { GHC.Types.I# x_aJh -> case w1_s1vk of { GHC.Types.I# y_aJk -> GHC.Types.I# (GHC.Prim.-# x_aJh y_aJk) } } } in
+        l1_s1uA
+          = case w_s1v1 of { GHC.Types.I# x_aJ8 -> case w1_s1v2 of { GHC.Types.I# y_aJb -> GHC.Types.I# (GHC.Prim.-# x_aJ8 y_aJb) } } } in
       let {
-        l2_s1uT :: [Int]
+        l2_s1uB :: [Int]
         [LclId, Unf=OtherCon []]
-        l2_s1uT = GHC.Types.: @Int l1_s1uS (GHC.Types.[] @Int) } in
+        l2_s1uB = GHC.Types.: @Int l1_s1uA (GHC.Types.[] @Int) } in
       let {
-        l3_sJv :: [Int]
+        l3_sJm :: [Int]
         [LclId, Unf=OtherCon []]
-        l3_sJv = GHC.Types.: @Int l_s1uR l2_s1uT } in
-      (# GHC.List.$w!! @Int l3_sJv 0#, GHC.List.$w!! @Int l3_sJv 1# #)
+        l3_sJm = GHC.Types.: @Int l_s1uz l2_s1uB } in
+      (# GHC.List.$w!! @Int l3_sJm 0#, GHC.List.$w!! @Int l3_sJm 1# #)
 
 -- RHS size: {terms: 10, types: 11, coercions: 0, joins: 0/0}
 pm [InlPrag=NOUSERINLINE[0]] :: Int -> Int -> (Int, Int)
@@ -35,9 +35,9 @@ pm [InlPrag=NOUSERINLINE[0]] :: Int -> Int -> (Int, Int)
  Cpr=m1,
  Unf=Unf{Src=InlineStable, TopLvl=True, Value=True, ConLike=True, WorkFree=True, Expandable=True,
          Guidance=ALWAYS_IF(arity=2,unsat_ok=True,boring_ok=False)
-         Tmpl= \ (w_s1vj [Occ=Once] :: Int) (w1_s1vk [Occ=Once] :: Int) ->
-                 case T10694.$wpm w_s1vj w1_s1vk of { (# ww1_s1vp [Occ=Once], ww2_s1vq [Occ=Once] #) -> (ww1_s1vp, ww2_s1vq) }}]
-pm = \ (w_s1vj :: Int) (w1_s1vk :: Int) -> case T10694.$wpm w_s1vj w1_s1vk of { (# ww1_s1vp, ww2_s1vq #) -> (ww1_s1vp, ww2_s1vq) }
+         Tmpl= \ (w_s1v1 [Occ=Once] :: Int) (w1_s1v2 [Occ=Once] :: Int) ->
+                 case T10694.$wpm w_s1v1 w1_s1v2 of { (# ww1_s1v7 [Occ=Once], ww2_s1v8 [Occ=Once] #) -> (ww1_s1v7, ww2_s1v8) }}]
+pm = \ (w_s1v1 :: Int) (w1_s1v2 :: Int) -> case T10694.$wpm w_s1v1 w1_s1v2 of { (# ww1_s1v7, ww2_s1v8 #) -> (ww1_s1v7, ww2_s1v8) }
 
 -- RHS size: {terms: 8, types: 9, coercions: 0, joins: 0/0}
 m :: Int -> Int -> Int
@@ -46,9 +46,9 @@ m :: Int -> Int -> Int
  Str=<L,U(U)><L,U(U)>,
  Unf=Unf{Src=InlineStable, TopLvl=True, Value=True, ConLike=True, WorkFree=True, Expandable=True,
          Guidance=ALWAYS_IF(arity=2,unsat_ok=True,boring_ok=False)
-         Tmpl= \ (x_awt [Occ=Once] :: Int) (y_awu [Occ=Once] :: Int) ->
-                 case pm x_awt y_awu of { (_ [Occ=Dead], mr_aww [Occ=Once]) -> mr_aww }}]
-m = \ (x_awt :: Int) (y_awu :: Int) -> case T10694.$wpm x_awt y_awu of { (# ww1_s1vp, ww2_s1vq #) -> ww2_s1vq }
+         Tmpl= \ (x_awo [Occ=Once] :: Int) (y_awp [Occ=Once] :: Int) ->
+                 case pm x_awo y_awp of { (_ [Occ=Dead], mr_awr [Occ=Once]) -> mr_awr }}]
+m = \ (x_awo :: Int) (y_awp :: Int) -> case T10694.$wpm x_awo y_awp of { (# ww1_s1v7, ww2_s1v8 #) -> ww2_s1v8 }
 
 -- RHS size: {terms: 1, types: 0, coercions: 0, joins: 0/0}
 T10694.$trModule4 :: GHC.Prim.Addr#
@@ -57,9 +57,7 @@ T10694.$trModule4 = "main"#
 
 -- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
 T10694.$trModule3 :: GHC.Types.TrName
-[GblId,
- Cpr=m1,
- Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 10 20}]
+[GblId, Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 10 20}]
 T10694.$trModule3 = GHC.Types.TrNameS T10694.$trModule4
 
 -- RHS size: {terms: 1, types: 0, coercions: 0, joins: 0/0}
@@ -69,17 +67,13 @@ T10694.$trModule2 = "T10694"#
 
 -- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
 T10694.$trModule1 :: GHC.Types.TrName
-[GblId,
- Cpr=m1,
- Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 10 20}]
+[GblId, Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 10 20}]
 T10694.$trModule1 = GHC.Types.TrNameS T10694.$trModule2
 
 -- RHS size: {terms: 3, types: 0, coercions: 0, joins: 0/0}
-T10694.$trModule :: GHC.Unit.Module
-[GblId,
- Cpr=m1,
- Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 10 30}]
-T10694.$trModule = GHC.Unit.Module T10694.$trModule3 T10694.$trModule1
+T10694.$trModule :: GHC.Types.Module
+[GblId, Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 10 30}]
+T10694.$trModule = GHC.Types.Module T10694.$trModule3 T10694.$trModule1
 
 
 
diff --git a/testsuite/tests/stranal/sigs/BottomFromInnerLambda.stderr b/testsuite/tests/stranal/sigs/BottomFromInnerLambda.stderr
index 259b5965e6..c3845dd6de 100644
--- a/testsuite/tests/stranal/sigs/BottomFromInnerLambda.stderr
+++ b/testsuite/tests/stranal/sigs/BottomFromInnerLambda.stderr
@@ -7,7 +7,7 @@ BottomFromInnerLambda.f: <S(S),1*U(U)>
 
 
 ==================== Cpr signatures ====================
-BottomFromInnerLambda.$trModule: m1
+BottomFromInnerLambda.$trModule:
 BottomFromInnerLambda.expensive: m1
 BottomFromInnerLambda.f:
 
diff --git a/testsuite/tests/stranal/sigs/CaseBinderCPR.stderr b/testsuite/tests/stranal/sigs/CaseBinderCPR.stderr
index cf95b806ec..54b0a44763 100644
--- a/testsuite/tests/stranal/sigs/CaseBinderCPR.stderr
+++ b/testsuite/tests/stranal/sigs/CaseBinderCPR.stderr
@@ -6,7 +6,7 @@ CaseBinderCPR.f_list_cmp: <L,C(C1(U(U)))><S,1*U><S,1*U>
 
 
 ==================== Cpr signatures ====================
-CaseBinderCPR.$trModule: m1
+CaseBinderCPR.$trModule:
 CaseBinderCPR.f_list_cmp: m1
 
 
diff --git a/testsuite/tests/stranal/sigs/DmdAnalGADTs.hs b/testsuite/tests/stranal/sigs/DmdAnalGADTs.hs
index 0c93cc0743..1a6d68a3b2 100644
--- a/testsuite/tests/stranal/sigs/DmdAnalGADTs.hs
+++ b/testsuite/tests/stranal/sigs/DmdAnalGADTs.hs
@@ -7,11 +7,13 @@ data D a where
     A :: D Int
     B :: D (Int -> Int)
 
+-- Doesn't have the CPR property anymore (#18154), but an expandable unfolding.
+-- The point of this test is that f' has the CPR property.
 hasCPR :: Int
 hasCPR = 1
 
 hasStrSig :: Int -> Int
-hasStrSig x = x
+hasStrSig x = x + 1
 
 diverges :: Int
 diverges = diverges
diff --git a/testsuite/tests/stranal/sigs/DmdAnalGADTs.stderr b/testsuite/tests/stranal/sigs/DmdAnalGADTs.stderr
index a42d492099..6dd5576da4 100644
--- a/testsuite/tests/stranal/sigs/DmdAnalGADTs.stderr
+++ b/testsuite/tests/stranal/sigs/DmdAnalGADTs.stderr
@@ -9,21 +9,21 @@ DmdAnalGADTs.f: <S,1*U>
 DmdAnalGADTs.f': <S,1*U>
 DmdAnalGADTs.g: <S,1*U>
 DmdAnalGADTs.hasCPR:
-DmdAnalGADTs.hasStrSig: <S,1*U>
+DmdAnalGADTs.hasStrSig: <S,1*U(U)>
 
 
 
 ==================== Cpr signatures ====================
-DmdAnalGADTs.$tc'A: m1
-DmdAnalGADTs.$tc'B: m1
-DmdAnalGADTs.$tcD: m1
-DmdAnalGADTs.$trModule: m1
+DmdAnalGADTs.$tc'A:
+DmdAnalGADTs.$tc'B:
+DmdAnalGADTs.$tcD:
+DmdAnalGADTs.$trModule:
 DmdAnalGADTs.diverges: b
 DmdAnalGADTs.f:
 DmdAnalGADTs.f': m1
 DmdAnalGADTs.g:
-DmdAnalGADTs.hasCPR: m1
-DmdAnalGADTs.hasStrSig:
+DmdAnalGADTs.hasCPR:
+DmdAnalGADTs.hasStrSig: m1
 
 
 
@@ -37,6 +37,6 @@ DmdAnalGADTs.f: <S,1*U>
 DmdAnalGADTs.f': <S,1*U>
 DmdAnalGADTs.g: <S,1*U>
 DmdAnalGADTs.hasCPR:
-DmdAnalGADTs.hasStrSig: <S,1*U>
+DmdAnalGADTs.hasStrSig: <S,1*U(U)>
 
 
diff --git a/testsuite/tests/stranal/sigs/HyperStrUse.stderr b/testsuite/tests/stranal/sigs/HyperStrUse.stderr
index 812115ec11..1ae91db4d4 100644
--- a/testsuite/tests/stranal/sigs/HyperStrUse.stderr
+++ b/testsuite/tests/stranal/sigs/HyperStrUse.stderr
@@ -6,7 +6,7 @@ HyperStrUse.f: <S(SL),1*U(1*U(U),A)><S,1*U>
 
 
 ==================== Cpr signatures ====================
-HyperStrUse.$trModule: m1
+HyperStrUse.$trModule:
 HyperStrUse.f: m1
 
 
diff --git a/testsuite/tests/stranal/sigs/NewtypeArity.stderr b/testsuite/tests/stranal/sigs/NewtypeArity.stderr
index 5519561d43..55cfe94ac7 100644
--- a/testsuite/tests/stranal/sigs/NewtypeArity.stderr
+++ b/testsuite/tests/stranal/sigs/NewtypeArity.stderr
@@ -9,9 +9,9 @@ Test.t2: <S,1*U(U)><S,1*U(U)>
 
 
 ==================== Cpr signatures ====================
-Test.$tc'MkT: m1
-Test.$tcT: m1
-Test.$trModule: m1
+Test.$tc'MkT:
+Test.$tcT:
+Test.$trModule:
 Test.t: m1
 Test.t2: m1
 
diff --git a/testsuite/tests/stranal/sigs/StrAnalExample.stderr b/testsuite/tests/stranal/sigs/StrAnalExample.stderr
index f18fb56998..eb2c5716bc 100644
--- a/testsuite/tests/stranal/sigs/StrAnalExample.stderr
+++ b/testsuite/tests/stranal/sigs/StrAnalExample.stderr
@@ -6,7 +6,7 @@ StrAnalExample.foo: <S,1*U>
 
 
 ==================== Cpr signatures ====================
-StrAnalExample.$trModule: m1
+StrAnalExample.$trModule:
 StrAnalExample.foo:
 
 
diff --git a/testsuite/tests/stranal/sigs/T12370.stderr b/testsuite/tests/stranal/sigs/T12370.stderr
index 63fa76d79d..caa780b0d2 100644
--- a/testsuite/tests/stranal/sigs/T12370.stderr
+++ b/testsuite/tests/stranal/sigs/T12370.stderr
@@ -7,7 +7,7 @@ T12370.foo: <S(SS),1*U(1*U(U),1*U(U))>
 
 
 ==================== Cpr signatures ====================
-T12370.$trModule: m1
+T12370.$trModule:
 T12370.bar: m1
 T12370.foo: m1
 
diff --git a/testsuite/tests/stranal/sigs/T17932.stderr b/testsuite/tests/stranal/sigs/T17932.stderr
index c086c8cd86..7ca56637df 100644
--- a/testsuite/tests/stranal/sigs/T17932.stderr
+++ b/testsuite/tests/stranal/sigs/T17932.stderr
@@ -10,11 +10,11 @@ T17932.flags: <S(SS),1*U(1*U,1*U)>
 
 
 ==================== Cpr signatures ====================
-T17932.$tc'Options: m1
-T17932.$tc'X: m1
-T17932.$tcOptions: m1
-T17932.$tcX: m1
-T17932.$trModule: m1
+T17932.$tc'Options:
+T17932.$tc'X:
+T17932.$tcOptions:
+T17932.$tcX:
+T17932.$trModule:
 T17932.flags:
 
 
diff --git a/testsuite/tests/stranal/sigs/T5075.stderr b/testsuite/tests/stranal/sigs/T5075.stderr
index 582f62d705..e048ce2fb3 100644
--- a/testsuite/tests/stranal/sigs/T5075.stderr
+++ b/testsuite/tests/stranal/sigs/T5075.stderr
@@ -6,7 +6,7 @@ T5075.loop: <S(LLC(C(S))LLLLL),U(A,A,C(C1(U)),A,A,A,A,A)><L,U(A,A,C(C1(U)),A,A,A
 
 
 ==================== Cpr signatures ====================
-T5075.$trModule: m1
+T5075.$trModule:
 T5075.loop:
 
 
diff --git a/testsuite/tests/stranal/sigs/T8569.stderr b/testsuite/tests/stranal/sigs/T8569.stderr
index 122f748775..bfbd22e52e 100644
--- a/testsuite/tests/stranal/sigs/T8569.stderr
+++ b/testsuite/tests/stranal/sigs/T8569.stderr
@@ -9,10 +9,10 @@ T8569.addUp: <S,1*U><L,U>
 
 
 ==================== Cpr signatures ====================
-T8569.$tc'Rdata: m1
-T8569.$tc'Rint: m1
-T8569.$tcRep: m1
-T8569.$trModule: m1
+T8569.$tc'Rdata:
+T8569.$tc'Rint:
+T8569.$tcRep:
+T8569.$trModule:
 T8569.addUp:
 
 
diff --git a/testsuite/tests/stranal/sigs/T8598.stderr b/testsuite/tests/stranal/sigs/T8598.stderr
index d6793609d3..8c56089bcd 100644
--- a/testsuite/tests/stranal/sigs/T8598.stderr
+++ b/testsuite/tests/stranal/sigs/T8598.stderr
@@ -6,7 +6,7 @@ T8598.fun: <S,1*U(U)>
 
 
 ==================== Cpr signatures ====================
-T8598.$trModule: m1
+T8598.$trModule:
 T8598.fun: m1
 
 
diff --git a/testsuite/tests/stranal/sigs/UnsatFun.stderr b/testsuite/tests/stranal/sigs/UnsatFun.stderr
index aedf131826..325d25ced7 100644
--- a/testsuite/tests/stranal/sigs/UnsatFun.stderr
+++ b/testsuite/tests/stranal/sigs/UnsatFun.stderr
@@ -12,7 +12,7 @@ UnsatFun.h3: <C(S),1*C1(U)>
 
 
 ==================== Cpr signatures ====================
-UnsatFun.$trModule: m1
+UnsatFun.$trModule:
 UnsatFun.f: b
 UnsatFun.g:
 UnsatFun.g':