[GHC] #14677: Code generator does not correctly tag a pointer

[GHC]

#14677: Code generator does not correctly tag a pointer
-------------------------------------+-------------------------------------
        Reporter:  simonpj           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:  14626
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by alexbiehl):

 Gabor,

 I have reduced your example down to
 {{{
 module Main where

 import GHC.Event
 import Prelude hiding (mod)

 f e2 = do
   print e2
   print (e2 == evtRead)

 main = f evtWrite
 }}}

 Expected output

 {{{
 [evtWrite]
 False
 }}}

 With Gabors branch we get

 {{{
 [evtRead]
 False
 }}}

 I compared CMM from a stock ghc-8.4 alpha vs. a GHC built from your
 branch. Really the only significant difference in CMM is

 (GHC from your branch)
 {{{
           ...
           R2 = PicBaseReg + (GHC.Event.Internal.evtWrite_closure+1);
           call Main.f1_info(R2) args: 8, res: 0, upd: 8;
           ...
 }}}

 (Stock ghc-8.4 alpha)
 {{{
           ...
           R2 = PicBaseReg + GHC.Event.Internal.evtWrite_closure;
           call Main.f1_info(R2) args: 8, res: 0, upd: 8;
           ...

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14677#comment:14>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler