Michael Gottesman e011e8ef82 [block-freq] Add BlockFrequency::scale that returns a remainder from the division and make the private scale in BlockFrequency more performant. ... This change is the first in a series of changes improving LLVM's Block Frequency propogation implementation to not lose probability mass in branchy code when propogating block frequency information from a basic block to its successors. This patch is a simple infrastructure improvement that does not actually modify the block frequency algorithm. The specific changes are: 1. Changes the division algorithm used when scaling block frequencies by branch probabilities to a short division algorithm. This gives us the remainder for free as well as provides a nice speed boost. When I benched the old routine and the new routine on a Sandy Bridge iMac with disabled turbo mode performing 8192 iterations on an array of length 32768, I saw ~600% increase in speed in mean/median performance. 2. Exposes a scale method that returns a remainder. This is important so we can ensure that when we scale a block frequency by some branch probability BP = N/D, the remainder from the division by D can be retrieved and propagated to other children to ensure no probability mass is lost (more to come on this). llvm-svn: 194950		2013-11-17 03:25:24 +00:00
..
llvm	[block-freq] Add BlockFrequency::scale that returns a remainder from the division and make the private scale in BlockFrequency more performant.	2013-11-17 03:25:24 +00:00
llvm-c	Add a loop rerolling pass	2013-11-16 23:59:05 +00:00