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.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120024 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 0 deletions

diff --git a/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index c04a6b2a62..b2919d8833 100644
--- a/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -91,6 +91,8 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
                                  I.hasNoUnsignedWrap(), TD))
     return ReplaceInstUsesWith(I, V);
 
+  if (Instruction *NV = SimplifyDistributed(I)) // (A*B)+(A*C) -> A*(B+C)
+    return NV;
   
   if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
     if (ConstantInt *CI = dyn_cast<ConstantInt>(RHSC)) {
@@ -548,6 +550,9 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
   if (Op0 == Op1)                        // sub X, X  -> 0
     return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
 
+  if (Instruction *NV = SimplifyDistributed(I)) // (A*B)-(A*C) -> A*(B-C)
+    return NV;
+  
   // If this is a 'B = x-(-A)', change to B = x+A.  This preserves NSW/NUW.
   if (Value *V = dyn_castNegVal(Op1)) {
     BinaryOperator *Res = BinaryOperator::CreateAdd(Op0, V);