#10677: slightly silly assembly for testing whether a Word# is 0## -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: bug | Status: patch Priority: low | Milestone: Component: Compiler | Version: 7.11 (CodeGen) | Resolution: | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: x86_64 Type of failure: Runtime | (amd64) performance bug | Test Case: Blocked By: | Blocking: Related Tickets: #10750 | Differential Revisions: Phab:D1137 -------------------------------------+------------------------------------- Comment (by rwbarton): Replying to [comment:3 nomeata]:
Is there a good way to have test cases for these issues?
I tried to fix this, but now (presumably due to a later optimization) it
Maybe grep `-ddump-opt-cmm` output for the condition `if (%MO_F_Gt_W64(...` and check that it compares something to 0, not 1? Replying to [comment:4 nomeata]: produces
{{{ testq %r14,%r14 jne _cQl }}}
I hope that is ok as well.
Yes, that's just as good (generally speaking, in any particular case one may be better than the other because they imply different basic block layouts, but understanding that is a whole separate issue). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10677#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler