StaticPointers pragma changes generated code even when the feature is not used

Tried with GHC HEAD. Program:

module Main where

import Control.Concurrent
import System.Mem

nats :: [Int]
nats = [0 .. ]

main = do
  let z = nats !! 400
  print z
  performGC
  threadDelay 1000000
  print (nats !! 900)

Compile without any flags:

==================== Tidy Core ====================
2019-02-04 09:16:26.121849511 UTC

Result size of Tidy Core
  = {terms: 45, types: 26, coercions: 0, joins: 0/0}

-- RHS size: {terms: 1, types: 0, coercions: 0, joins: 0/0}
$trModule1_r1zg :: GHC.Prim.Addr#
[GblId, Caf=NoCafRefs, Unf=OtherCon []]
$trModule1_r1zg = "main"#

-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
$trModule2_r1zt :: GHC.Types.TrName
[GblId, Caf=NoCafRefs, Unf=OtherCon []]
$trModule2_r1zt = GHC.Types.TrNameS $trModule1_r1zg

-- RHS size: {terms: 1, types: 0, coercions: 0, joins: 0/0}
$trModule3_r1zu :: GHC.Prim.Addr#
[GblId, Caf=NoCafRefs, Unf=OtherCon []]
$trModule3_r1zu = "Main"#

-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
$trModule4_r1zv :: GHC.Types.TrName
[GblId, Caf=NoCafRefs, Unf=OtherCon []]
$trModule4_r1zv = GHC.Types.TrNameS $trModule3_r1zu

-- RHS size: {terms: 3, types: 0, coercions: 0, joins: 0/0}
Main.$trModule :: GHC.Types.Module
[GblId, Caf=NoCafRefs, Unf=OtherCon []]
Main.$trModule = GHC.Types.Module $trModule2_r1zt $trModule4_r1zv

-- RHS size: {terms: 4, types: 1, coercions: 0, joins: 0/0}
nats :: [Int]
[GblId]
nats = enumFrom @ Int GHC.Enum.$fEnumInt (GHC.Types.I# 0#)

-- RHS size: {terms: 22, types: 13, coercions: 0, joins: 0/0}
main :: IO ()
[GblId]
main
  = >>
      @ IO
      GHC.Base.$fMonadIO
      @ ()
      @ ()
      (print
         @ Int GHC.Show.$fShowInt (!! @ Int nats (GHC.Types.I# 400#)))
      (>>
         @ IO
         GHC.Base.$fMonadIO
         @ ()
         @ ()
         performGC
         (>>
            @ IO
            GHC.Base.$fMonadIO
            @ ()
            @ ()
            (threadDelay (GHC.Types.I# 1000000#))
            (print
               @ Int GHC.Show.$fShowInt (!! @ Int nats (GHC.Types.I# 900#)))))

-- RHS size: {terms: 2, types: 1, coercions: 0, joins: 0/0}
:Main.main :: IO ()
[GblId]
:Main.main = GHC.TopHandler.runMainIO @ () main

Compile with -XStaticPointers:

==================== Tidy Core ====================
2019-02-04 09:16:35.678350955 UTC

Result size of Tidy Core
  = {terms: 67, types: 42, coercions: 0, joins: 0/0}

-- RHS size: {terms: 1, types: 0, coercions: 0, joins: 0/0}
$trModule1_r1zg :: GHC.Prim.Addr#
[GblId, Caf=NoCafRefs, Unf=OtherCon []]
$trModule1_r1zg = "main"#

-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
$trModule2_r1zF :: GHC.Types.TrName
[GblId, Caf=NoCafRefs, Unf=OtherCon []]
$trModule2_r1zF = GHC.Types.TrNameS $trModule1_r1zg

-- RHS size: {terms: 1, types: 0, coercions: 0, joins: 0/0}
$trModule3_r1zG :: GHC.Prim.Addr#
[GblId, Caf=NoCafRefs, Unf=OtherCon []]
$trModule3_r1zG = "Main"#

-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
$trModule4_r1zH :: GHC.Types.TrName
[GblId, Caf=NoCafRefs, Unf=OtherCon []]
$trModule4_r1zH = GHC.Types.TrNameS $trModule3_r1zG

-- RHS size: {terms: 3, types: 0, coercions: 0, joins: 0/0}
Main.$trModule :: GHC.Types.Module
[GblId, Caf=NoCafRefs, Unf=OtherCon []]
Main.$trModule = GHC.Types.Module $trModule2_r1zF $trModule4_r1zH

-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
lvl_r1zI :: Int
[GblId, Caf=NoCafRefs, Unf=OtherCon []]
lvl_r1zI = GHC.Types.I# 0#

-- RHS size: {terms: 3, types: 1, coercions: 0, joins: 0/0}
nats :: [Int]
[GblId]
nats = enumFrom @ Int GHC.Enum.$fEnumInt lvl_r1zI

-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
lvl1_r1zJ :: Int
[GblId, Caf=NoCafRefs, Unf=OtherCon []]
lvl1_r1zJ = GHC.Types.I# 400#

-- RHS size: {terms: 3, types: 1, coercions: 0, joins: 0/0}
lvl2_r1zK :: Int
[GblId]
lvl2_r1zK = !! @ Int nats lvl1_r1zJ

-- RHS size: {terms: 3, types: 1, coercions: 0, joins: 0/0}
lvl3_r1zL :: IO ()
[GblId]
lvl3_r1zL = print @ Int GHC.Show.$fShowInt lvl2_r1zK

-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
lvl4_r1zM :: Int
[GblId, Caf=NoCafRefs, Unf=OtherCon []]
lvl4_r1zM = GHC.Types.I# 1000000#

-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
lvl5_r1zN :: IO ()
[GblId]
lvl5_r1zN = threadDelay lvl4_r1zM

-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
lvl6_r1zO :: Int
[GblId, Caf=NoCafRefs, Unf=OtherCon []]
lvl6_r1zO = GHC.Types.I# 900#

-- RHS size: {terms: 3, types: 1, coercions: 0, joins: 0/0}
lvl7_r1zP :: Int
[GblId]
lvl7_r1zP = !! @ Int nats lvl6_r1zO

-- RHS size: {terms: 3, types: 1, coercions: 0, joins: 0/0}
lvl8_r1zQ :: IO ()
[GblId]
lvl8_r1zQ = print @ Int GHC.Show.$fShowInt lvl7_r1zP

-- RHS size: {terms: 4, types: 3, coercions: 0, joins: 0/0}
lvl9_r1zR :: IO ()
[GblId]
lvl9_r1zR
  = >> @ IO GHC.Base.$fMonadIO @ () @ () lvl5_r1zN lvl8_r1zQ

-- RHS size: {terms: 4, types: 3, coercions: 0, joins: 0/0}
lvl10_r1zS :: IO ()
[GblId]
lvl10_r1zS
  = >> @ IO GHC.Base.$fMonadIO @ () @ () performGC lvl9_r1zR

-- RHS size: {terms: 4, types: 3, coercions: 0, joins: 0/0}
main :: IO ()
[GblId]
main = >> @ IO GHC.Base.$fMonadIO @ () @ () lvl3_r1zL lvl10_r1zS

-- RHS size: {terms: 2, types: 1, coercions: 0, joins: 0/0}
:Main.main :: IO ()
[GblId]
:Main.main = GHC.TopHandler.runMainIO @ () main

Diff:

--- no_static_ptrs/GcStaticPointers.dump-simpl	2019-02-04 12:16:26.120066655 +0300
+++ static_ptrs/GcStaticPointers.dump-simpl	2019-02-04 12:16:35.675924328 +0300
@@ -1,9 +1,9 @@
 
 ==================== Tidy Core ====================
-2019-02-04 09:16:26.121849511 UTC
+2019-02-04 09:16:35.678350955 UTC
 
 Result size of Tidy Core
-  = {terms: 45, types: 26, coercions: 0, joins: 0/0}
+  = {terms: 67, types: 42, coercions: 0, joins: 0/0}
 
 -- RHS size: {terms: 1, types: 0, coercions: 0, joins: 0/0}
 $trModule1_r1zg :: GHC.Prim.Addr#
@@ -11,55 +11,91 @@
 $trModule1_r1zg = "main"#
 
 -- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
-$trModule2_r1zt :: GHC.Types.TrName
+$trModule2_r1zF :: GHC.Types.TrName
 [GblId, Caf=NoCafRefs, Unf=OtherCon []]
-$trModule2_r1zt = GHC.Types.TrNameS $trModule1_r1zg
+$trModule2_r1zF = GHC.Types.TrNameS $trModule1_r1zg
 
 -- RHS size: {terms: 1, types: 0, coercions: 0, joins: 0/0}
-$trModule3_r1zu :: GHC.Prim.Addr#
+$trModule3_r1zG :: GHC.Prim.Addr#
 [GblId, Caf=NoCafRefs, Unf=OtherCon []]
-$trModule3_r1zu = "Main"#
+$trModule3_r1zG = "Main"#
 
 -- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
-$trModule4_r1zv :: GHC.Types.TrName
+$trModule4_r1zH :: GHC.Types.TrName
 [GblId, Caf=NoCafRefs, Unf=OtherCon []]
-$trModule4_r1zv = GHC.Types.TrNameS $trModule3_r1zu
+$trModule4_r1zH = GHC.Types.TrNameS $trModule3_r1zG
 
 -- RHS size: {terms: 3, types: 0, coercions: 0, joins: 0/0}
 Main.$trModule :: GHC.Types.Module
 [GblId, Caf=NoCafRefs, Unf=OtherCon []]
-Main.$trModule = GHC.Types.Module $trModule2_r1zt $trModule4_r1zv
+Main.$trModule = GHC.Types.Module $trModule2_r1zF $trModule4_r1zH
 
--- RHS size: {terms: 4, types: 1, coercions: 0, joins: 0/0}
+-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
+lvl_r1zI :: Int
+[GblId, Caf=NoCafRefs, Unf=OtherCon []]
+lvl_r1zI = GHC.Types.I# 0#
+
+-- RHS size: {terms: 3, types: 1, coercions: 0, joins: 0/0}
 nats :: [Int]
 [GblId]
-nats = enumFrom @ Int GHC.Enum.$fEnumInt (GHC.Types.I# 0#)
+nats = enumFrom @ Int GHC.Enum.$fEnumInt lvl_r1zI
+
+-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
+lvl1_r1zJ :: Int
+[GblId, Caf=NoCafRefs, Unf=OtherCon []]
+lvl1_r1zJ = GHC.Types.I# 400#
+
+-- RHS size: {terms: 3, types: 1, coercions: 0, joins: 0/0}
+lvl2_r1zK :: Int
+[GblId]
+lvl2_r1zK = !! @ Int nats lvl1_r1zJ
+
+-- RHS size: {terms: 3, types: 1, coercions: 0, joins: 0/0}
+lvl3_r1zL :: IO ()
+[GblId]
+lvl3_r1zL = print @ Int GHC.Show.$fShowInt lvl2_r1zK
+
+-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
+lvl4_r1zM :: Int
+[GblId, Caf=NoCafRefs, Unf=OtherCon []]
+lvl4_r1zM = GHC.Types.I# 1000000#
+
+-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
+lvl5_r1zN :: IO ()
+[GblId]
+lvl5_r1zN = threadDelay lvl4_r1zM
+
+-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
+lvl6_r1zO :: Int
+[GblId, Caf=NoCafRefs, Unf=OtherCon []]
+lvl6_r1zO = GHC.Types.I# 900#
+
+-- RHS size: {terms: 3, types: 1, coercions: 0, joins: 0/0}
+lvl7_r1zP :: Int
+[GblId]
+lvl7_r1zP = !! @ Int nats lvl6_r1zO
+
+-- RHS size: {terms: 3, types: 1, coercions: 0, joins: 0/0}
+lvl8_r1zQ :: IO ()
+[GblId]
+lvl8_r1zQ = print @ Int GHC.Show.$fShowInt lvl7_r1zP
+
+-- RHS size: {terms: 4, types: 3, coercions: 0, joins: 0/0}
+lvl9_r1zR :: IO ()
+[GblId]
+lvl9_r1zR
+  = >> @ IO GHC.Base.$fMonadIO @ () @ () lvl5_r1zN lvl8_r1zQ
+
+-- RHS size: {terms: 4, types: 3, coercions: 0, joins: 0/0}
+lvl10_r1zS :: IO ()
+[GblId]
+lvl10_r1zS
+  = >> @ IO GHC.Base.$fMonadIO @ () @ () performGC lvl9_r1zR
 
--- RHS size: {terms: 22, types: 13, coercions: 0, joins: 0/0}
+-- RHS size: {terms: 4, types: 3, coercions: 0, joins: 0/0}
 main :: IO ()
 [GblId]
-main
-  = >>
-      @ IO
-      GHC.Base.$fMonadIO
-      @ ()
-      @ ()
-      (print
-         @ Int GHC.Show.$fShowInt (!! @ Int nats (GHC.Types.I# 400#)))
-      (>>
-         @ IO
-         GHC.Base.$fMonadIO
-         @ ()
-         @ ()
-         performGC
-         (>>
-            @ IO
-            GHC.Base.$fMonadIO
-            @ ()
-            @ ()
-            (threadDelay (GHC.Types.I# 1000000#))
-            (print
-               @ Int GHC.Show.$fShowInt (!! @ Int nats (GHC.Types.I# 900#)))))
+main = >> @ IO GHC.Base.$fMonadIO @ () @ () lvl3_r1zL lvl10_r1zS
 
 -- RHS size: {terms: 2, types: 1, coercions: 0, joins: 0/0}
 :Main.main :: IO ()

Trac metadata

Trac field	Value
Version
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
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Blocking
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StaticPointers pragma changes generated code even when the feature is not used