#7411: Exceptions are optimized away in certain situations -------------------------------------+------------------------------------- Reporter: SimonHengel | Owner: tdammers Type: bug | Status: new Priority: high | Milestone: 8.8.1 Component: Compiler | Version: 7.6.1 Resolution: | Keywords: seq, deepseq, | evaluate, exceptions Operating System: Linux | Architecture: x86_64 | (amd64) Type of failure: Incorrect result | Test Case: at runtime | simplCore/should_fail/T7411 Blocked By: | Blocking: Related Tickets: #5129 #15225 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by tdammers): OK, so it turns out that make clean doesn't actually clean things up thoroughly enough. I did another test run, building both GHC and nofib from a fresh checkout for each run, and now everything works just fine. So it seems that the core dumps I got earlier were somehow caused by artifacts from a previous build still being in the build tree somewhere; clearly if you link things together in ways they weren't meant to, strange behavior is to be expected. Now armed with that, and a fixed `fasta` implementation from #15225, I managed to do six nofib runs; the interesting ones are: - Both GHC and nofib compiled with the state hack in place - this is the current situation (`nofibrun-gs_ns2.log`) - GHC with the state hack, nofib compiled with `-fno-state-hack` (`nofibrun-gs-nn2.log` - Both GHC and nofib compiled with `-fno-state-hack` (`nofibrun- gn_nn2.log`) Results from nofib-analyse attached; key takeaway however is that the difference overall is small and slightly in favor of removing the state hack. A few interesting deviations that stand out: - GHC compiled with `-fno-state-hack` consistently produces larger binaries, by about 5% - Programs compiled with a GHC compiled with `-fno-state-hack` run faster by 3.2% on average, but there is a lot of deviation - Most of the above improvements seem to be from more efficient GC - Compile times differ drastically; vanilla GHC compiling programs with `-fno-state-hack` is 23.6% faster on average than the same compiler with the state hack; compiling GHC itself with `-fno-state-hack` and then compiling the nofib suite also with `-fno-state-hack` is almost 50% faster than compiling everything normally. The difference in allocations is even more whopping, with 35.5% and 58.3% respectively. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/7411#comment:43 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler