I have always wondered why this stuff was an annotation instead of a pragma in the first place. Making it a pragma sounds like a great idea to me, but I have no idea whether or not there's a good reason to make ForceSpecConstr an annotation instead. Geoff On 10/09/2013 10:13 AM, Austin Seipp wrote:
Hello all,
Early last week I was reminded of something, which was that vector/dph depend on the stage2 compiler - this is because both packages use annotations to specify ForceSpecConstr and NoSpecConstr on several key datatypes.
For most of our platforms (now including ARM,) this should generally be OK, because we have stage2 and the linker available to support it.
But in particular, it makes vector and dph unusable for cross compilers. This might be somewhat problematic for e.g. iOS or an RPi, where we only have a stage1 cross compiler - but it's reasonable to assume we may want to use vector there! And more and more libraries depend on vector these days.
I believe these are the only instances in which vector/dph needs stage2. So I ask: is it reasonable to change this to a pragma built into the compiler? That is,
------------------------------------------------------------ data SPEC = SPEC | SPEC2 {-# ANN type SPEC ForceSpecConstr #-}
data PArray a = PArray Int# (PData a) {-# ANN type PArray NoSpecConstr #-} -------------------------------------------------------------
becomes something like:
------------------------------------------------------------- data SPEC = SPEC | SPEC2 {-# SPECIALIZE Constructor SPEC #-}
data PArray a = PArray Int# (PData a) {-# NOSPECIALIZE Constructor PArray #-} -------------------------------------------------------------
I'm not particularly interested in a bikeshedding discussion about the exact syntax for the pragma (although this somewhat falls in line with 'INLINE ConLike' as a special case,) - I just want to know if this sounds reasonable.
Looking at SpecConstr in the compiler, there seems to be quite a lot of note summarising that we need a better design - in particular, notes about nuking NoSpecConstr (as it appeared before ForceSpecConstr,) and turning ForceSpecConstr into a library type of some sort. I don't propose changing any of this really, just removing the dependency on the annotations.
But if someone thinks a library type would be better suited for this - I'm totally fine with that too and am all-ears for a suggestion.
And of course, both of these can continue to be supported for a while, although the patches to vector, at least, would be trivial to switch it over.
Ben, Manuel, Simon - you three are the experts here I believe. Thoughts? Perhaps I'm missing something key here?