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, 32 insertions, 12 deletions

diff --git a/testsuite/tests/deSugar/should_compile/T2431.stderr b/testsuite/tests/deSugar/should_compile/T2431.stderr
index 797c6c7776..a8da44b73f 100644
--- a/testsuite/tests/deSugar/should_compile/T2431.stderr
+++ b/testsuite/tests/deSugar/should_compile/T2431.stderr
@@ -1,6 +1,6 @@
 
 ==================== Tidy Core ====================
-Result size of Tidy Core = {terms: 36, types: 30, coercions: 1}
+Result size of Tidy Core = {terms: 44, types: 34, coercions: 1}
 
 -- RHS size: {terms: 2, types: 4, coercions: 1}
 T2431.$WRefl [InlPrag=INLINE] :: forall a. a :~: a
@@ -21,25 +21,40 @@ absurd :: forall a. (Int :~: Bool) -> a
 [GblId, Arity=1, Caf=NoCafRefs, Str=<L,U>x]
 absurd = \ (@ a) (x :: Int :~: Bool) -> case x of { }
 
--- RHS size: {terms: 2, types: 0, coercions: 0}
-$trModule1 :: GHC.Types.TrName
+-- RHS size: {terms: 1, types: 0, coercions: 0}
+$trModule1 :: GHC.Prim.Addr#
 [GblId, Caf=NoCafRefs]
-$trModule1 = GHC.Types.TrNameS "main"#
+$trModule1 = "main"#
 
 -- RHS size: {terms: 2, types: 0, coercions: 0}
 $trModule2 :: GHC.Types.TrName
 [GblId, Caf=NoCafRefs]
-$trModule2 = GHC.Types.TrNameS "T2431"#
+$trModule2 = GHC.Types.TrNameS $trModule1
+
+-- RHS size: {terms: 1, types: 0, coercions: 0}
+$trModule3 :: GHC.Prim.Addr#
+[GblId, Caf=NoCafRefs]
+$trModule3 = "T2431"#
+
+-- RHS size: {terms: 2, types: 0, coercions: 0}
+$trModule4 :: GHC.Types.TrName
+[GblId, Caf=NoCafRefs]
+$trModule4 = GHC.Types.TrNameS $trModule3
 
 -- RHS size: {terms: 3, types: 0, coercions: 0}
 T2431.$trModule :: GHC.Types.Module
 [GblId, Caf=NoCafRefs]
-T2431.$trModule = GHC.Types.Module $trModule1 $trModule2
+T2431.$trModule = GHC.Types.Module $trModule2 $trModule4
+
+-- RHS size: {terms: 1, types: 0, coercions: 0}
+$tc'Refl1 :: GHC.Prim.Addr#
+[GblId, Caf=NoCafRefs]
+$tc'Refl1 = "'Refl"#
 
 -- RHS size: {terms: 2, types: 0, coercions: 0}
-$tc'Refl1 :: GHC.Types.TrName
+$tc'Refl2 :: GHC.Types.TrName
 [GblId, Caf=NoCafRefs]
-$tc'Refl1 = GHC.Types.TrNameS "'Refl"#
+$tc'Refl2 = GHC.Types.TrNameS $tc'Refl1
 
 -- RHS size: {terms: 5, types: 0, coercions: 0}
 T2431.$tc'Refl :: GHC.Types.TyCon
@@ -49,12 +64,17 @@ T2431.$tc'Refl =
     15026191172322750497##
     3898273167927206410##
     T2431.$trModule
-    $tc'Refl1
+    $tc'Refl2
+
+-- RHS size: {terms: 1, types: 0, coercions: 0}
+$tc:~:1 :: GHC.Prim.Addr#
+[GblId, Caf=NoCafRefs]
+$tc:~:1 = ":~:"#
 
 -- RHS size: {terms: 2, types: 0, coercions: 0}
-$tc:~:1 :: GHC.Types.TrName
+$tc:~:2 :: GHC.Types.TrName
 [GblId, Caf=NoCafRefs]
-$tc:~:1 = GHC.Types.TrNameS ":~:"#
+$tc:~:2 = GHC.Types.TrNameS $tc:~:1
 
 -- RHS size: {terms: 5, types: 0, coercions: 0}
 T2431.$tc:~: :: GHC.Types.TyCon
@@ -64,7 +84,7 @@ T2431.$tc:~: =
     9759653149176674453##
     12942818337407067047##
     T2431.$trModule
-    $tc:~:1
+    $tc:~:2