[Haskell] Expecting more inlining for bit shifting

roconnor at theorem.ca roconnor at theorem.ca
Mon Oct 9 10:33:47 EDT 2006

On Mon, 9 Oct 2006, Simon Peyton-Jones wrote:

> Turns out that 'shift' is just too big to be inlined.  (It's only called
> once, but you have exported it too.)
> You can see GHC's inlining decisions by saying -ddump-inlinings.
> To make GHC keener to inline, use an INLINE pragma, or increase the
> inlining size threshold e.g. -funfolding-threshold=12

Okay, when I force inlining for shift, (and I even need to do it for shiftR!) 
then the code is inlined in C.  However this isn't the behaviour I want. 
Ideally the inlining should only happen when/because the second argument of 
shift is constant and the system knows that it can evaluate the case analysis 
away and that makes the function small.

Am I being too naive on what to expect from my complier or is this reasonable?

PS, is there a way to mark an imported instance of a class function 
(Data.Bits.shift for Data.Word.Word32) to be inlined?

Russell O'Connor                                      <http://r6.ca/>
``All talk about `theft,''' the general counsel of the American Graphophone
Company wrote, ``is the merest claptrap, for there exists no property in
ideas musical, literary or artistic, except as defined by statute.''

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