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.

6 files changed, 9 insertions, 9 deletions

diff --git a/testsuite/tests/simplCore/should_compile/T13143.stderr b/testsuite/tests/simplCore/should_compile/T13143.stderr
index ec423d7b4a..86094fe7d9 100644
--- a/testsuite/tests/simplCore/should_compile/T13143.stderr
+++ b/testsuite/tests/simplCore/should_compile/T13143.stderr
@@ -90,7 +90,7 @@ g [InlPrag=[2]] :: Bool -> Bool -> Int -> Int
 [GblId,
  Arity=3,
  Str=<1L><1L><1P(L)>,
- Cpr=m1,
+ Cpr=1,
  Unf=Unf{Src=InlineStable, TopLvl=True, Value=True, ConLike=True,
          WorkFree=True, Expandable=True,
          Guidance=ALWAYS_IF(arity=3,unsat_ok=True,boring_ok=False)
diff --git a/testsuite/tests/simplCore/should_compile/T13543.stderr b/testsuite/tests/simplCore/should_compile/T13543.stderr
index 32e34ea559..90bda9792f 100644
--- a/testsuite/tests/simplCore/should_compile/T13543.stderr
+++ b/testsuite/tests/simplCore/should_compile/T13543.stderr
@@ -8,8 +8,8 @@ Foo.g: <1P(1P(L),1P(L))>
 
 ==================== Cpr signatures ====================
 Foo.$trModule:
-Foo.f: m1
-Foo.g: m1
+Foo.f: 1
+Foo.g: 1
 
 
 
diff --git a/testsuite/tests/simplCore/should_compile/T3717.stderr b/testsuite/tests/simplCore/should_compile/T3717.stderr
index 69b1766a84..f33b8ec401 100644
--- a/testsuite/tests/simplCore/should_compile/T3717.stderr
+++ b/testsuite/tests/simplCore/should_compile/T3717.stderr
@@ -57,7 +57,7 @@ foo [InlPrag=[2]] :: Int -> Int
 [GblId,
  Arity=1,
  Str=<1P(1L)>,
- Cpr=m1,
+ Cpr=1,
  Unf=Unf{Src=InlineStable, TopLvl=True, Value=True, ConLike=True,
          WorkFree=True, Expandable=True,
          Guidance=ALWAYS_IF(arity=1,unsat_ok=True,boring_ok=False)
diff --git a/testsuite/tests/simplCore/should_compile/T4930.stderr b/testsuite/tests/simplCore/should_compile/T4930.stderr
index 04e065f51c..66d257897e 100644
--- a/testsuite/tests/simplCore/should_compile/T4930.stderr
+++ b/testsuite/tests/simplCore/should_compile/T4930.stderr
@@ -57,7 +57,7 @@ foo [InlPrag=[2]] :: Int -> Int
 [GblId,
  Arity=1,
  Str=<1P(L)>,
- Cpr=m1,
+ Cpr=1,
  Unf=Unf{Src=InlineStable, TopLvl=True, Value=True, ConLike=True,
          WorkFree=True, Expandable=True,
          Guidance=ALWAYS_IF(arity=1,unsat_ok=True,boring_ok=False)
diff --git a/testsuite/tests/simplCore/should_compile/T7360.stderr b/testsuite/tests/simplCore/should_compile/T7360.stderr
index 0b45e8a390..fe869c7c40 100644
--- a/testsuite/tests/simplCore/should_compile/T7360.stderr
+++ b/testsuite/tests/simplCore/should_compile/T7360.stderr
@@ -9,7 +9,7 @@ T7360.$WFoo3 [InlPrag=INLINE[final] CONLIKE] :: Int %1 -> Foo
  Arity=1,
  Caf=NoCafRefs,
  Str=<SL>,
- Cpr=m3,
+ Cpr=3,
  Unf=Unf{Src=InlineStable, TopLvl=True, Value=True, ConLike=True,
          WorkFree=True, Expandable=True,
          Guidance=ALWAYS_IF(arity=1,unsat_ok=True,boring_ok=False)
@@ -36,7 +36,7 @@ fun2 :: forall {a}. [a] -> ((), Int)
 [GblId,
  Arity=1,
  Str=<ML>,
- Cpr=m1,
+ Cpr=1,
  Unf=Unf{Src=InlineStable, TopLvl=True, Value=True, ConLike=True,
          WorkFree=True, Expandable=True,
          Guidance=ALWAYS_IF(arity=1,unsat_ok=True,boring_ok=False)
diff --git a/testsuite/tests/simplCore/should_compile/spec-inline.stderr b/testsuite/tests/simplCore/should_compile/spec-inline.stderr
index 683ff4d6ac..319eba03cb 100644
--- a/testsuite/tests/simplCore/should_compile/spec-inline.stderr
+++ b/testsuite/tests/simplCore/should_compile/spec-inline.stderr
@@ -112,7 +112,7 @@ Roman.foo_go [InlPrag=[2]] :: Maybe Int -> Maybe Int -> Int
 [GblId,
  Arity=2,
  Str=<1L><1L>,
- Cpr=m1,
+ Cpr=1,
  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)
@@ -144,7 +144,7 @@ foo :: Int -> Int
 [GblId,
  Arity=1,
  Str=<1P(L)>,
- Cpr=m1,
+ Cpr=1,
  Unf=Unf{Src=InlineStable, TopLvl=True, Value=True, ConLike=True,
          WorkFree=True, Expandable=True,
          Guidance=ALWAYS_IF(arity=1,unsat_ok=True,boring_ok=False)