[PATCH] [Reassocate] Add support for vector instructions.

[Sanjay Patel]

Hi Chad -

Thanks for posting this patch. I wasn't able to apply the patch cleanly to r217455, so I'm not sure if that is affecting what I'm seeing. 

I think @test20 in test/Transforms/Reassociate/vector-basictests.ll should cover what I'm trying to do in DAGCombiner here:
http://reviews.llvm.org/D5254

It seems to work when there's a 'fast' directly on the fmuls, but not if I specify "unsafe-fp-math=true" as a function attribute or via the "enable-unsafe-fp-math" parameter to opt. I guess this a general question: what are we supposed to be using to detect -ffast-math and friends? Do we have to consider both the IR flags and the attributes/params?

http://reviews.llvm.org/D5222