Zubin pushed to branch wip/9.12.3-backports at Glasgow Haskell Compiler / GHC

Commits:

• 357867fc
  by Luite Stegeman at 2025-09-12T17:02:08+05:30

  Add flags for switching off speculative evaluation.
  
  We found that speculative evaluation can increase the amount of
  allocations in some circumstances. This patch adds new flags for
  selectively disabling speculative evaluation, allowing us to
  test the effect of the optimization.
  
  The new flags are:
  
    -fspec-eval
       globally enable speculative evaluation
  
    -fspec-eval-dictfun
       enable speculative evaluation for dictionary functions (no effect
       if speculative evaluation is globally disabled)
  
  The new flags are on by default for all optimisation levels.
  
  See #25284
  
  (cherry picked from commit 2309975247543a4f77009ea5c3c7a8ebe06dc60b)
  

1 changed file:

• compiler/GHC/CoreToStg/Prep.hs

Changes:

     is_hnf      = exprIsHNF rhs

     dmd         = idDemandInfo bndr

     is_strict   = isStrUsedDmd dmd

+

     ok_for_spec = exprOkForSpecEval call_ok_for_spec rhs

     -- See Note [Controlling Speculative Evaluation]

     call_ok_for_spec x