#14226: Common Block Elimination pass doesn't eliminate common blocks -------------------------------------+------------------------------------- Reporter: bgamari | Owner: bgamari Type: bug | Status: new Priority: high | Milestone: 8.6.1 Component: Compiler | Version: 8.2.1 (CodeGen) | Keywords: newcomer, Resolution: | CodeGen Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #9157, #14754 | Differential Rev(s): Phab:D3973, Wiki Page: | Phab:D3999 -------------------------------------+------------------------------------- Comment (by michalt): :( I can currently think of two options: 1) Fix the approach using alpha renaming by actually checking liveness on entry and exit for each variable. (to only consider variables that are not live across blocks) The disadvantage is that this would be quite a bit more costly. 2) Don't improve CBE itself, but run it a second time after the sinking pass - this might get rid of some of the cases from this ticket (e.g., the one from comment:6) The advantage is that this would also fix #12915; the disadvantage: this might not be always as effective as option 1). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14226#comment:28 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler