[GHC] #16197: Strictness is not preserved under -O1

[GHC]

#16197: Strictness is not preserved under -O1
-------------------------------------+-------------------------------------
           Reporter:  alang9         |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.4.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Incorrect result
  Unknown/Multiple                   |  at runtime
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 With -O0, the attached code prints:

 {{{
 > /usr/local/ghc/ghc-8.4.1.0/bin/ghc -O0 src/foo.hs; and ./src/foo
 [1 of 1] Compiling Main             ( src/foo.hs, src/foo.o )
 [Optimisation flags changed]
 Linking src/foo ...
 ("exec",0)
 ("depth",0)
 ("exec",1)
 ("depth",0)
 }}}

 But with -O1, it prints:

 {{{
 > /usr/local/ghc/ghc-8.4.1.0/bin/ghc -O1 src/foo.hs; and ./src/foo
 [1 of 1] Compiling Main             ( src/foo.hs, src/foo.o )
 Linking src/foo ...
 ("depth",0)
 ("depth",0)
 }}}

 Reproduced with 8.4.1 and 8.6.2. Doesn't seem to happen under 8.2.0

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16197>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler