Yes, it's quite possible, given f, a, g, and b of different kinds, to make `f
a` and `g b` have the same *kind*. But how could they ever be the same type?
Ah I see. Good point.
Anyway, the conclusion is that decomposing a well-kinded (f a ~ g b) into
ill-kinded goals is indeed a bad thing, so
I was thinking about my response, and realized there was one major
misleading thing in my description. The load reordering I described
applies to load instructions in C-- proper, i.e. things that show up
in the C-- dup as:
W_ x = I64[...addr...]
Reads to IORefs and reads to vectors get
Second, the optimizer is a bit more conservative when it comes to
primop calls (internally referred to as unsafe foreign calls)
Sorry, I need to correct myself here. Foreign primops, and most
out-of-line primops, compile into jumps which end basic blocks, which
constitute hard boundaries since
I suspect it's not by design, because there's certainly plans to make them
inline primops, and the reordering issue of the cmm optimizer hasn't come
up in the design discussion previously. (And I should add those notes to
the associated tickets)
On Tuesday, December 31, 2013, Edward Z. Yang
