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

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombine.h b/llvm/lib/Transforms/InstCombine/InstCombine.h
index 05846d0f9e1..b492777a472 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombine.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombine.h
@@ -290,6 +290,12 @@ private:
   /// operators which are associative or commutative.
   bool SimplifyAssociativeOrCommutative(BinaryOperator &I);
 
+  /// SimplifyDistributed - This tries to simplify binary operations which some
+  /// other binary operation distributes over (eg "A*B+A*C" -> "A*(B+C)" since
+  /// addition is distributed over by multiplication).  Returns the result of
+  /// the simplification, or null if no simplification was performed.
+  Instruction *SimplifyDistributed(BinaryOperator &I);
+
   /// SimplifyDemandedUseBits - Attempts to replace V with a simpler value
   /// based on the demanded bits.
   Value *SimplifyDemandedUseBits(Value *V, APInt DemandedMask,