Compiler memory use regression

I have a module which compiles fine with ghc 7.6, but where ghc 7.8.2 runs out of memory (32-bit Windows). Sadly, I cannot supply the source code since it's proprietary, so I realize that this bug will be almost impossible to fix. It is possible to compile the module with -O0 and -O1, but not -O2. (This is a very performance critical module so I'd like -O2.)

Trac metadata

Trac field	Value
Version	7.8.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
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changed weight to 5

added Tbug Trac import labels

This is probably #8960 (closed). Is it possible for you to turn off SpecConstr with -fno-spec-constr and see what difference it makes in compilation time and resulting executable speed?

Yes, turning off SpecConstr makes it work. Thanks for the workaround!

Can you try to compile your module with either HEAD (the master branch) or the ghc-7.8 branch? Those branches contain the following bug fix, which should solve your problem:

commit af4bc31c50c873344a2426d4be842f92edf17019
Author: Simon Peyton Jones <simonpj@microsoft.com>
Date:   Mon Aug 25 12:28:44 2014 +0100

    Do not duplicate call information in SpecConstr (Trac #8852)
    
    This long-standing and egregious bug meant that call information was
    being gratuitously copied, leading to an exponential blowup in the
    number of calls to be examined when function definitions are deeply
    nested.  That is what has been causing the blowup in SpecConstr's
    running time, not (as I had previously supposed) generating very large code.
    
    See Note [spec_usg includes rhs_usg]

Trac metadata

Trac field	Value
Related	→ #5550 (closed), #7068 (closed), #7898 (closed), #7944 (closed), #8836 (closed), #8852 (closed), #8941 (closed), #8960 (closed), #8980 (closed)

I will test it when there's a win-32 ghc-7.8.4.

closed

Please reopen if this is still a problem.

You can get ghc-7.8.4 for 32-bit windows here: https://www.haskell.org/ghc/download_ghc_7_8_4#windows

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedWorksForMe

added compiler perf label

added Pnormal label