On 24 November 2005 11:07, Bulat Ziganshin wrote:
Hello Matt,
Thursday, November 24, 2005, 7:52:23 AM, you wrote:
int64ToWord64# = unsafeCoerce# word64ToInt64# = unsafeCoerce#
(W32# x#) + (W32# y#) = W32# (narrow32Word# (x# `plusWord#` y#)) (W64# x#) + (W64# y#) = W64# (int64ToWord64# (word64ToInt64# x# `plusInt64#` word64ToInt64# y#))
The definitions are those used on a 32-bit architecture. So, when it is cheap the plusWord# function is used, but when it is "relatively expensive" then extra conversions are added. Wouldn't it make sense to avoid the conversions in all cases, regardless of whether they are free or not?
i'm agree that code simplification you already done is anyway Right Thing. so it's better to apply your patch AND add abovementioned definitions to help any other operations. about int32ToWord32# and so on - they are defined through stg primitives, so anyway defining them as unsafeCoerce# must make things a little faster
No, using a primitive for int32ToWord32# is better, because the compiler knows about primitives and can apply constant-folding. For example int32ToWord32# 0# could turn directly into a Word32# value. Also, unsafeCoerce# must be retained in the Core language, because Core is typed, even though it compiles to no code. Its presence in Core might hinder certain optimisations. We should really have proper primitives for all these 64-bit operations, rather than using FFI calls. Cheers, Simon