[Haskell-cafe] To LLVM or not to LLVM...

Ian Ross ian at skybluetrades.net
Tue Jan 28 15:56:56 UTC 2014

Hi Peter,

> I would assume that everybody who wants to compile your package with
> LLVM can simply configure the build with "--ghc-option=-fllvm", no?

Absolutely, yes.  I was just wondering about it as a matter of policy,
particularly in terms of reverse dependencies (not that this package has
any yet).  If you install package A that depends on package B and package B
gets a big performance boost from LLVM, things are fine if you install
package B yourself and tell Cabal to build it with LLVM, but if Cabal
installs it automatically as a dependency of package A, then it won't get
built with LLVM (unless you install package A with that option too, but
then you end up pushing the responsibility to handle package B's
peculiarities upstream to its reverse dependencies).

> A Cabal flag for the same purpose might make sense, IMHO, if there are
> other build parameters that change when compiling with LLVM (like CPP
> defines, etc.), but it's my understanding that this is not the case?

Right.  I think I'll add a Cabal flag and worry about the reverse
dependencies issue if the package ever has any!



Ian Ross   Tel: +43(0)6804451378   ian at skybluetrades.net
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