Nested CPR light (#19398)

While fixing #19232, it became increasingly clear that the vestigial
hack described in `Note [Optimistic field binder CPR]` is complicated
and causes reboxing. Rather than make the hack worse, this patch
gets rid of it completely in favor of giving deeply unboxed parameters
the Nested CPR property. Example:
```hs
f :: (Int, Int) -> Int
f p = case p of
 (x, y) | x == y    = x
        | otherwise = y
```
Based on `p`'s `idDemandInfo` `1P(1P(L),1P(L))`, we can see that both
fields of `p` will be available unboxed. As a result, we give `p` the
nested CPR property `1(1,1)`. When analysing the `case`, the field
CPRs are transferred to the binders `x` and `y`, respectively, so that
we ultimately give `f` the CPR property.

I took the liberty to do a bit of refactoring:

- I renamed `CprResult` ("Constructed product result result") to plain
  `Cpr`.
- I Introduced `FlatConCpr` in addition to (now nested) `ConCpr` and
  and according pattern synonym that rewrites flat `ConCpr` to
  `FlatConCpr`s, purely for compiler perf reasons.
- Similarly for performance reasons, we now store binders with a
  Top signature in a separate `IntSet`,
  see `Note [Efficient Top sigs in SigEnv]`.
- I moved a bit of stuff around in `GHC.Core.Opt.WorkWrap.Utils` and
  introduced `UnboxingDecision` to replace the `Maybe DataConPatContext`
  type we used to return from `wantToUnbox`.
- Since the `Outputable Cpr` instance changed anyway, I removed the
  leading `m` which we used to emit for `ConCpr`. It's just noise,
  especially now that we may output nested CPRs.

Fixes #19398.

8 files changed, 12 insertions, 12 deletions

diff --git a/testsuite/tests/stranal/sigs/BottomFromInnerLambda.stderr b/testsuite/tests/stranal/sigs/BottomFromInnerLambda.stderr
index 7b954564a7..c1fa7f22e6 100644
--- a/testsuite/tests/stranal/sigs/BottomFromInnerLambda.stderr
+++ b/testsuite/tests/stranal/sigs/BottomFromInnerLambda.stderr
@@ -8,7 +8,7 @@ BottomFromInnerLambda.f: <1P(SL)>
 
 ==================== Cpr signatures ====================
 BottomFromInnerLambda.$trModule:
-BottomFromInnerLambda.expensive: m1
+BottomFromInnerLambda.expensive: 1
 BottomFromInnerLambda.f:
 
 
diff --git a/testsuite/tests/stranal/sigs/DmdAnalGADTs.stderr b/testsuite/tests/stranal/sigs/DmdAnalGADTs.stderr
index 8f70d7d5e0..4cbc565ee2 100644
--- a/testsuite/tests/stranal/sigs/DmdAnalGADTs.stderr
+++ b/testsuite/tests/stranal/sigs/DmdAnalGADTs.stderr
@@ -20,10 +20,10 @@ DmdAnalGADTs.$tcD:
 DmdAnalGADTs.$trModule:
 DmdAnalGADTs.diverges: b
 DmdAnalGADTs.f:
-DmdAnalGADTs.f': m1
+DmdAnalGADTs.f': 1
 DmdAnalGADTs.g:
 DmdAnalGADTs.hasCPR:
-DmdAnalGADTs.hasStrSig: m1
+DmdAnalGADTs.hasStrSig: 1
 
 
 
diff --git a/testsuite/tests/stranal/sigs/HyperStrUse.stderr b/testsuite/tests/stranal/sigs/HyperStrUse.stderr
index e8a806e4ad..09829ae4fa 100644
--- a/testsuite/tests/stranal/sigs/HyperStrUse.stderr
+++ b/testsuite/tests/stranal/sigs/HyperStrUse.stderr
@@ -7,7 +7,7 @@ HyperStrUse.f: <1P(1P(L),A)><1L>
 
 ==================== Cpr signatures ====================
 HyperStrUse.$trModule:
-HyperStrUse.f: m1
+HyperStrUse.f: 1
 
 
 
diff --git a/testsuite/tests/stranal/sigs/NewtypeArity.stderr b/testsuite/tests/stranal/sigs/NewtypeArity.stderr
index 5a73b53524..66a810f5a5 100644
--- a/testsuite/tests/stranal/sigs/NewtypeArity.stderr
+++ b/testsuite/tests/stranal/sigs/NewtypeArity.stderr
@@ -12,8 +12,8 @@ Test.t2: <1P(L)><1P(L)>
 Test.$tc'MkT:
 Test.$tcT:
 Test.$trModule:
-Test.t: m1
-Test.t2: m1
+Test.t: 1
+Test.t2: 1
 
 
 
diff --git a/testsuite/tests/stranal/sigs/T12370.stderr b/testsuite/tests/stranal/sigs/T12370.stderr
index d557b437b1..ac5eb53888 100644
--- a/testsuite/tests/stranal/sigs/T12370.stderr
+++ b/testsuite/tests/stranal/sigs/T12370.stderr
@@ -8,8 +8,8 @@ T12370.foo: <1P(1P(L),1P(L))>
 
 ==================== Cpr signatures ====================
 T12370.$trModule:
-T12370.bar: m1
-T12370.foo: m1
+T12370.bar: 1
+T12370.foo: 1
 
 
 
diff --git a/testsuite/tests/stranal/sigs/T18957.stderr b/testsuite/tests/stranal/sigs/T18957.stderr
index 2beea34dfb..6795bf0dab 100644
--- a/testsuite/tests/stranal/sigs/T18957.stderr
+++ b/testsuite/tests/stranal/sigs/T18957.stderr
@@ -14,7 +14,7 @@ T18957.$trModule:
 T18957.g:
 T18957.h1:
 T18957.h2:
-T18957.h3: m1
+T18957.h3: 1
 T18957.seq':
 
 
diff --git a/testsuite/tests/stranal/sigs/T8598.stderr b/testsuite/tests/stranal/sigs/T8598.stderr
index 9f49534945..db7c97f807 100644
--- a/testsuite/tests/stranal/sigs/T8598.stderr
+++ b/testsuite/tests/stranal/sigs/T8598.stderr
@@ -7,7 +7,7 @@ T8598.fun: <1P(L)>
 
 ==================== Cpr signatures ====================
 T8598.$trModule:
-T8598.fun: m1
+T8598.fun: 1
 
 
 
diff --git a/testsuite/tests/stranal/sigs/UnsatFun.stderr b/testsuite/tests/stranal/sigs/UnsatFun.stderr
index 691fe21c98..b3ccac6f6e 100644
--- a/testsuite/tests/stranal/sigs/UnsatFun.stderr
+++ b/testsuite/tests/stranal/sigs/UnsatFun.stderr
@@ -16,10 +16,10 @@ UnsatFun.$trModule:
 UnsatFun.f: b
 UnsatFun.g:
 UnsatFun.g':
-UnsatFun.g3: m1
+UnsatFun.g3: 1
 UnsatFun.h:
 UnsatFun.h2:
-UnsatFun.h3: m1
+UnsatFun.h3: 1