[GHC] #10528: compile time performance regression with OverloadedStrings and Text (was: compile time performance regression on big literal)

[GHC]

#10528: compile time performance regression with OverloadedStrings and Text
-------------------------------------+-------------------------------------
        Reporter:  jakewheat         |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  high              |               Milestone:  7.10.3
       Component:  Compiler          |                 Version:  7.10.2-rc2
      Resolution:                    |                Keywords:
Operating System:  Linux             |            Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
-------------------------------------+-------------------------------------
Changes (by thomie):

 * priority:  normal => high
 * version:   => 7.10.2-rc2
 * milestone:   => 7.10.3


Comment:

 I can reproduce this with the test below. Compiling with `7.10.2` takes
 more than 10x longer than with `7.10.1`.

 {{{
 {-# LANGUAGE OverloadedStrings #-}

 module T10528 where

 import Data.Text (Text)

 strings :: [Text]
 strings = [
   "abstime", "aclitem", "bit", "bool", "box", "bpchar", "bytea", "char",
   "cid", "cidr", "circle", "date", "float4", "float8", "gtsvector",
 "inet",
   "interval", "json", "jsonb", "line", "lseg", "macaddr", "money", "name",
   "numeric", "oid", "oidvector", "path", "pg_lsn", "pg_node_tree",
 "point",
   "polygon", "refcursor", "regclass", "regconfig", "regdictionary",
 "regoper",
   "regoperator", "regproc", "regprocedure", "regtype", "reltime", "smgr",
   "text", "tid", "time", "timestamp", "timestamptz", "timetz",
 "tinterval",
   "tsquery", "tsvector", "txid_snapshot", "unknown", "uuid", "varbit",
   "varchar", "xid", "bit", "bool", "box", "bpchar", "bytea", "char",
 "cid",
   "cidr", "circle", "date", "float4", "float8", "gtsvector", "inet",
 "int2",
   "int2vector", "int4", "int8", "interval", "json", "jsonb", "line",
 "lseg",
   "macaddr", "money", "name", "numeric", "oid", "oidvector", "path",
 "pg_lsn",
   "pg_node_tree", "point", "polygon", "refcursor", "regclass",
 "regconfig",
   "regdictionary", "regoper", "regoperator", "regproc", "regprocedure",
   "regtype", "reltime", "smgr", "text", "tid", "time", "timestamp",
   "timestamptz", "timetz", "tinterval", "tsquery", "tsvector",
   "txid_snapshot", "unknown", "uuid", "varbit", "varchar", "xid", "xml"
   ]
 }}}

 {{{
 $ cabal install text

 $ ghc-7.10.1 T10528.hs -c -fforce-recomp -Rghc-timing -O
 <<ghc: 186739648 bytes, 94 GCs, 4318989/12392440 avg/max bytes residency
 (7 samples), 28M in use, 0.001 INIT (0.004 elapsed), 0.332 MUT (0.387
 elapsed), 0.328 GC (0.395 elapsed) :ghc>

 $ ghc-7.10.2 T10528.hs -c -fforce-recomp -Rghc-timing -O
 <<ghc: 2719125976 bytes, 440 GCs, 16808138/34792080 avg/max bytes
 residency (13 samples), 97M in use, 0.001 INIT (0.001 elapsed), 6.439 MUT
 (10.141 elapsed), 2.795 GC (4.449 elapsed) :ghc>>
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10528#comment:2>
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