Unfortunately, we're not talking seconds, but coffee-breaks of linking times on our Sun (yes, the stuff is in the range of a large compiler - we're fortunate enough to be able to build on rather substantial third-party packages, think haskell-in-haskell frontend distributed over unusually many modules + strategic traversal support + our own code).
And yes, I was worried about NFS-mounting first, especially since linking on our Sun takes even longer than on our PCs (long breaks instead of short ones;-), but moving .hi and .o to local tmp-space didn't speed things up (then again, it's a large machine, and our disk setup is likely to be more complex than I know - I'll have to check with our admins).
It does sound like it's taking rather too long, I'd investigate further.
Alternative a: use someone else's incremental linker, e.g., Sun's ild (ghc's -pgml option appears to have its own idea about option formatting, btw) - this doesn't seem to work - should it?
You'd probably want to call the incremental linker directly rather than using GHC - what exactly does it do, BTW? What files does it generate?
Calling it via GHC seemed the best way to ensure that it gets everything it needs (what else would be the purpose of -pgml?).
Ah I see - it's just like a normal linker, except it takes a previous version of the executable and attempts to just re-link the bits it needs? GHC has some built-in assumptions about the linker: it must accept gcc-style command line options. This probably isn't true of the incremental linker, so you could either (a) write a wrapper around it, or (b) arrange to call the incremental linker through gcc. I can't remember if (b) is possible, but a quick scan of the docs suggested that gcc doesn't have the equivalent of -pgml so (b) might be out. BTW, -pgml is usually just used to select a different version of gcc (as with -pgmc).
Alternative b: convince ghc to link objects in stages, e.g., on a per-directory basis - gnu's ld seems to support at least this kind of partial linking (-i/-r). Not quite as nice as a fully incremental linker, but would probably save our day..
Yes, this works fine. We use it to build the libraries for GHCi.
Presumably directed via Makefiles? Could this please be automated for ghc --make?
It's easy: $ ld -r -o All.o A.o B.o C.o ... Cheers, Simon