#14565: Performance degrades from -O1 to -O2 -------------------------------------+------------------------------------- Reporter: dbeacham | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: x86_64 Type of failure: Runtime | (amd64) performance bug | Test Case: Blocked By: | Blocking: Related Tickets: #14379 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Description changed by dbeacham: Old description:
GHC seems to get stuck at SpecConstr stage when compiling. Cpu and memory usage then sky rocket.
I've managed to get the example down to what appears to be minimal but making a number of minor changes makes the compilation go through quickly:
* changing `toIdx` to `const 0` * removing one of the `V.forM_` layers. * using "-fno-spec-constr" (unsuprisingly).
I can't reproduce it on 8.0.2.
New description: GHC seems to get stuck at SpecConstr stage when compiling. I've managed to get the example down to what appears to be minimal but making a number of minor changes makes the compilation go through quickly: * changing `toIdx` to `const 0` * removing one of the `V.forM_` layers. * using "-fno-spec-constr" (unsuprisingly). I can't reproduce it on 8.0.2. In larger examples I was able to get memory and cpu to sky rocket quite quickly but I appear to have lost some of that behaviour when paring down the example. -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14565#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler