instcombine: fold (x & y) | (~x & z) and (x & y) ^ (~x & z) into ((y ^ z) & x) ^ z which is one instruction shorter. (PR6773)

before:
  %and = and i32 %y, %x
  %neg = xor i32 %x, -1
  %and4 = and i32 %z, %neg
  %xor = xor i32 %and4, %and

after:
  %xor1 = xor i32 %z, %y
  %and2 = and i32 %xor1, %x
  %xor = xor i32 %and2, %z

llvm-svn: 108136

1 files changed, 17 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 8586054fce0..3bfeba11cc2 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1584,6 +1584,14 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
     if ((match(A, m_Not(m_Specific(B))) &&
          match(D, m_Not(m_Specific(C)))))
       return BinaryOperator::CreateXor(C, B);
+
+    // (A & ~C) | (B & C) -> ((B ^ A) & C) ^ A
+    if (Op0->hasOneUse() && Op1->hasOneUse() &&
+        match(C, m_Not(m_Specific(D)))) {
+      Value *Xor = Builder->CreateXor(B, A, "xor");
+      Value *And = Builder->CreateAnd(Xor, D, "and");
+      return BinaryOperator::CreateXor(And, A);
+    }
   }
   
   // (X >> Z) | (Y >> Z)  -> (X|Y) >> Z  for all shifts.
@@ -1920,6 +1928,15 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
         return BinaryOperator::CreateAnd(NewOp, X);
       }
     }
+
+    // (A & ~C) ^ (B & C) -> ((B ^ A) & C) ^ A
+    if (Op0->hasOneUse() && Op1->hasOneUse() &&
+        match(Op0I, m_And(m_Value(A), m_Not(m_Value(D)))) &&
+        match(Op1I, m_And(m_Value(B), m_Value(D)))) {
+      Value *Xor = Builder->CreateXor(B, A, "xor");
+      Value *And = Builder->CreateAnd(Xor, D, "and");
+      return BinaryOperator::CreateXor(And, A);
+    }
   }
     
   // (icmp1 A, B) ^ (icmp2 A, B) --> (icmp3 A, B)