Benjamin Kramer 4a40190f76 Add the missing sub identity "A-(A-B) -> B" to DAGCombine.
This happens e.g. for code like "X - X%10" where we lower the modulo operation
to a series of multiplies and shifts that are then subtracted from X, leading to
this missed optimization.

llvm-svn: 124532
2011-01-29 12:34:05 +00:00
..
2011-01-27 14:44:55 +00:00