On Wednesday, 15 January 2014 at 01:42:07 UTC, Manu wrote:
Right, thanks for that.
I'm quite surprised by how bad that turned out actually, and
with LDC,
which is usually the best at optimising that sort of thing.
Need to do some intensive experimentation... but this is a bit
concerning.
GCC might do some loop merging, I haven't checked. It's just that
this pattern doesn't tend to appear too much in traditional C/C++
code (after all, who splits up their loops into two parts just
for fun?), so it could be that the LLVM people just never really
bothered to write a pass to merge single loops that have been
split (as opposed to classical loop fusion, where the loop ranges
are the same, but the operations performed/target data different).
Maybe it would be possible to implement something like this
fairly easily using the existing LLVM loop analyses though.
David
