More aggressive dictionary removal?

Simon Peyton Jones simonpj at microsoft.com
Thu Jan 28 14:31:31 UTC 2016


I think the difference between the inlinable and specialize pragma is whether the specialization needs to be driven by the call site or not. If you have a handful of known types you want to specialize for up front, you can use the specialize pragma. If the set is large or unknown (like in the case of container keys/value, the inlinable pragma does the right thing.)
Correct!  And not well described anywhere.

If someone writes something, I’ll willingly review

S

From: Johan Tibell [mailto:johan.tibell at gmail.com]
Sent: 28 January 2016 13:40
To: Simon Peyton Jones <simonpj at microsoft.com>
Cc: Conal Elliott <conal at conal.net>; ghc-devs at haskell.org
Subject: Re: More aggressive dictionary removal?

I think the difference between the inlinable and specialize pragma is whether the specialization needs to be driven by the call site or not. If you have a handful of known types you want to specialize for up front, you can use the specialize pragma. If the set is large or unknown (like in the case of container keys/value, the inlinable pragma does the right thing.)

On Thu, Jan 28, 2016 at 1:54 PM, Simon Peyton Jones <simonpj at microsoft.com<mailto:simonpj at microsoft.com>> wrote:
Aggressive inlining is one way, but specialisation ought to get a long way, and makes fewer copies of the specialised code.

It’s hard to help without a concrete example

Simon

From: ghc-devs [mailto:ghc-devs-bounces at haskell.org<mailto:ghc-devs-bounces at haskell.org>] On Behalf Of Conal Elliott
Sent: 28 January 2016 00:05
To: ghc-devs at haskell.org<mailto:ghc-devs at haskell.org>
Subject: More aggressive dictionary removal?

I'm looking for pointers on getting GHC to eliminate more overloading & polymorphism. I think this sort of thing mainly happens in the Specialise module. The default GHC flag settings get me a couple levels of monomorphization and dictionary removal, but I want to go further. I've tried -fspecialise-aggressively, but it didn't seem to make a difference, and I haven't found this flag described in the GHC user's guide. Anyone have pointers to more information?
Thanks, - Conal

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