Allow top-level string literals in Core (#8472)

This commits relaxes the invariants of the Core syntax so that a
top-level variable can be bound to a primitive string literal of type
Addr#.

This commit:

* Relaxes the invatiants of the Core, and allows top-level bindings whose
  type is Addr# as long as their RHS is either a primitive string literal or
  another variable.

* Allows the simplifier and the full-laziness transformer to float out
  primitive string literals to the top leve.

* Introduces the new StgGenTopBinding type to accomodate top-level Addr#
  bindings.

* Introduces a new type of labels in the object code, with the suffix "_bytes",
  for exported top-level Addr# bindings.

* Makes some built-in rules more robust. This was necessary to keep them
  functional after the above changes.

This is a continuation of D2554.

Rebasing notes:
This had two slightly suspicious performance regressions:

* T12425: bytes allocated regressed by roughly 5%
* T4029: bytes allocated regressed by a bit over 1%
* T13035: bytes allocated regressed by a bit over 5%

These deserve additional investigation.

Rebased by: bgamari.

Test Plan: ./validate --slow

Reviewers: goldfire, trofi, simonmar, simonpj, austin, hvr, bgamari

Reviewed By: trofi, simonpj, bgamari

Subscribers: trofi, simonpj, gridaphobe, thomie

Differential Revision: https://phabricator.haskell.org/D2605

GHC Trac Issues: #8472

1 files changed, 23 insertions, 7 deletions

diff --git a/testsuite/tests/numeric/should_compile/T7116.stdout b/testsuite/tests/numeric/should_compile/T7116.stdout
index 9f7837bdc7..7fe4d93d87 100644
--- a/testsuite/tests/numeric/should_compile/T7116.stdout
+++ b/testsuite/tests/numeric/should_compile/T7116.stdout
@@ -1,15 +1,31 @@
 
 ==================== Tidy Core ====================
-Result size of Tidy Core = {terms: 46, types: 23, coercions: 0}
+Result size of Tidy Core = {terms: 50, types: 25, coercions: 0}
+
+-- RHS size: {terms: 1, types: 0, coercions: 0}
+T7116.$trModule4 :: GHC.Prim.Addr#
+[GblId,
+ Caf=NoCafRefs,
+ Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True,
+         WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 20 0}]
+T7116.$trModule4 = "main"#
 
 -- RHS size: {terms: 2, types: 0, coercions: 0}
-T7116.$trModule2 :: GHC.Types.TrName
+T7116.$trModule3 :: GHC.Types.TrName
 [GblId,
  Caf=NoCafRefs,
  Str=m1,
  Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True,
-         WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 30 20}]
-T7116.$trModule2 = GHC.Types.TrNameS "main"#
+         WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 10 20}]
+T7116.$trModule3 = GHC.Types.TrNameS T7116.$trModule4
+
+-- RHS size: {terms: 1, types: 0, coercions: 0}
+T7116.$trModule2 :: GHC.Prim.Addr#
+[GblId,
+ Caf=NoCafRefs,
+ Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True,
+         WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 30 0}]
+T7116.$trModule2 = "T7116"#
 
 -- RHS size: {terms: 2, types: 0, coercions: 0}
 T7116.$trModule1 :: GHC.Types.TrName
@@ -17,8 +33,8 @@ T7116.$trModule1 :: GHC.Types.TrName
  Caf=NoCafRefs,
  Str=m1,
  Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True,
-         WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 40 20}]
-T7116.$trModule1 = GHC.Types.TrNameS "T7116"#
+         WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 10 20}]
+T7116.$trModule1 = GHC.Types.TrNameS T7116.$trModule2
 
 -- RHS size: {terms: 3, types: 0, coercions: 0}
 T7116.$trModule :: GHC.Types.Module
@@ -28,7 +44,7 @@ T7116.$trModule :: GHC.Types.Module
  Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True,
          WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 10 30}]
 T7116.$trModule =
-  GHC.Types.Module T7116.$trModule2 T7116.$trModule1
+  GHC.Types.Module T7116.$trModule3 T7116.$trModule1
 
 -- RHS size: {terms: 8, types: 3, coercions: 0}
 dr :: Double -> Double