InstCombine: Combine (add (and %a, %b) (or %a, %b)) to (add %a, %b)

What follows bellow is a correctness proof of the transform using CVC3.

$ < t.cvc
A, B : BITVECTOR(32);

QUERY BVPLUS(32, A & B, A | B) = BVPLUS(32, A, B);

$ cvc3 < t.cvc
Valid.

llvm-svn: 215400

1 files changed, 23 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index ed0e1c90888..b18c10dd57b 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1240,7 +1240,7 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
     }
   }
 
-  // Check for (x & y) + (x ^ y)
+  // (add (xor A, B) (and A, B)) --> (or A, B)
   {
     Value *A = nullptr, *B = nullptr;
     if (match(RHS, m_Xor(m_Value(A), m_Value(B))) &&
@@ -1254,6 +1254,28 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
       return BinaryOperator::CreateOr(A, B);
   }
 
+  // (add (or A, B) (and A, B)) --> (add A, B)
+  {
+    Value *A = nullptr, *B = nullptr;
+    if (match(RHS, m_Or(m_Value(A), m_Value(B))) &&
+        (match(LHS, m_And(m_Specific(A), m_Specific(B))) ||
+         match(LHS, m_And(m_Specific(B), m_Specific(A))))) {
+      auto *New = BinaryOperator::CreateAdd(A, B);
+      New->setHasNoSignedWrap(I.hasNoSignedWrap());
+      New->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
+      return New;
+    }
+
+    if (match(LHS, m_Or(m_Value(A), m_Value(B))) &&
+        (match(RHS, m_And(m_Specific(A), m_Specific(B))) ||
+         match(RHS, m_And(m_Specific(B), m_Specific(A))))) {
+      auto *New = BinaryOperator::CreateAdd(A, B);
+      New->setHasNoSignedWrap(I.hasNoSignedWrap());
+      New->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
+      return New;
+    }
+  }
+
   // TODO(jingyue): Consider WillNotOverflowSignedAdd and
   // WillNotOverflowUnsignedAdd to reduce the number of invocations of
   // computeKnownBits.