Exploit distributive laws (eg: And distributes over Or, Mul over Add, etc) in a
fairly systematic way in instcombine. Some of these cases were already dealt with, in which case I removed the existing code. The case of Add has a bunch of funky logic which covers some of this plus a few variants (considers shifts to be a form of multiplication), which I didn't touch. The simplification performed is: A*B+A*C -> A*(B+C). The improvement is to do this in cases that were not already handled [such as A*B-A*C -> A*(B-C), which was reported on the mailing list], and also to do it more often by not checking for "only one use" if "B+C" simplifies. llvm-svn: 120024
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