[GHC] #14914: Only turn suitable targets into a fallthrough in CmmContFlowOpt.

[GHC]

#14914: Only turn suitable targets into a fallthrough in CmmContFlowOpt.
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           Reporter:  AndreasK       |             Owner:  (none)
               Type:  task           |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:
  (CodeGen)                          |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 We are inverting Branches in CmmContFlowOpt such that we get as many fall
 through paths as possible.

 However as it stands besides the conditionals themselves the only
 criterion used is the number of predecessors for a Block.

 This often (but not always) aligns with the actual possibility of turning
 branches into a fallthrough.

 We should at least look at the cost/benefit of tracking actual
 predecessors and see if that turns out as something worthwhile.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14914>
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