On 11/06/2012, at 18:52, Evan Laforge wrote:
> On Tue, May 29, 2012 at 12:52 PM, Roman Leshchinskiy <[email protected]>
> wrote:
>>
>> Vector should definitely fuse this, if it doesn't it's a bug. Please report
>> if it doesn't for you. To verify, just count the number of letrecs in the
>> optimised Core. You'll see one letrec if it has been fused and two if it
>> hasn't.
>
> I see two letrecs in find_before2, but both of them are on findIndex.
> I only have one findIndex so I'm not sure what's going on. The first
> one calls the second, but there's an boxed Either argument in there,
> which must be coming out of vector internals.
Hmm, which version of GHC and what compiler flags are you using? I'm not
familiar with ghc-core, maybe that's doing something wrong. Just run ghc -O2
-ddump-simpl and look at the output. Below is the code I'm getting for
find_before2 with 7.4.2. As you can see, everything has been fused (although I
notice that GHC isn't pushing x_a11p and y1_a124 into the branches for some
reason, looks like a new regression but not a particularly bad one and nothing
to do with fusion).
find_before2_rkk :: Int -> Vector Int -> Int
[GblId, Arity=2, Caf=NoCafRefs, Str=DmdType LU(LLL)m]
find_before2_rkk =
\ (n_arE :: Int) (vec_arF :: Vector Int) ->
case vec_arF `cast` ...
of _ { Vector ipv_s2Jf ipv1_s2Jg ipv2_s2Jh ->
case n_arE of _ { I# y_a11t ->
case ># 0 y_a11t of _ {
False ->
letrec {
$sfindIndex_loop_s2Qz [Occ=LoopBreaker]
:: Int# -> Int# -> Int# -> Id (Maybe Int)
[LclId, Arity=3, Str=DmdType LLL]
$sfindIndex_loop_s2Qz =
\ (sc_s2Q8 :: Int#) (sc1_s2Q9 :: Int#) (sc2_s2Qa :: Int#) ->
case >=# sc_s2Q8 ipv1_s2Jg of _ {
False ->
case indexIntArray# ipv2_s2Jh (+# ipv_s2Jf sc_s2Q8)
of wild_a2JM { __DEFAULT ->
let {
x_a11p [Dmd=Just L] :: Int#
[LclId, Str=DmdType]
x_a11p = +# sc1_s2Q9 wild_a2JM } in
case ># x_a11p y_a11t of _ {
False ->
$sfindIndex_loop_s2Qz (+# sc_s2Q8 1) x_a11p (+# sc2_s2Qa
1);
True -> (Just @ Int (I# sc2_s2Qa)) `cast` ...
}
};
True -> (Nothing @ Int) `cast` ...
}; } in
case ($sfindIndex_loop_s2Qz 0 0 1) `cast` ... of _ {
Nothing -> lvl_r2QO;
Just i_arH ->
case i_arH of _ { I# x_a11Q ->
let {
y1_a124 [Dmd=Just L] :: Int#
[LclId, Str=DmdType]
y1_a124 = -# x_a11Q 1 } in
case <=# 0 y1_a124 of _ {
False -> lvl_r2QO;
True -> I# y1_a124
}
}
};
True -> lvl_r2QO
}
}
}
Roman
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