1 files changed, 16 insertions, 20 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 4314b2b0a37..3871b8ab636 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1123,26 +1123,6 @@ static Instruction *matchDeMorgansLaws(BinaryOperator &I,
         return BinaryOperator::CreateNot(LogicOp);
       }
 
-  // De Morgan's Law in disguise:
-  // (zext(bool A) ^ 1) & (zext(bool B) ^ 1) -> zext(~(A | B))
-  // (zext(bool A) ^ 1) | (zext(bool B) ^ 1) -> zext(~(A & B))
-  Value *A = nullptr;
-  Value *B = nullptr;
-  ConstantInt *C1 = nullptr;
-  if (match(Op0, m_OneUse(m_Xor(m_ZExt(m_Value(A)), m_ConstantInt(C1)))) &&
-      match(Op1, m_OneUse(m_Xor(m_ZExt(m_Value(B)), m_Specific(C1))))) {
-    // TODO: This check could be loosened to handle different type sizes.
-    // Alternatively, we could fix the definition of m_Not to recognize a not
-    // operation hidden by a zext?
-    if (A->getType()->isIntegerTy(1) && B->getType()->isIntegerTy(1) &&
-        C1->isOne()) {
-      Value *LogicOp = Builder->CreateBinOp(Opcode, A, B,
-                                            I.getName() + ".demorgan");
-      Value *Not = Builder->CreateNot(LogicOp);
-      return CastInst::CreateZExtOrBitCast(Not, I.getType());
-    }
-  }
-
   return nullptr;
 }
 
@@ -1199,6 +1179,22 @@ Instruction *InstCombiner::foldCastedBitwiseLogic(BinaryOperator &I) {
     return CastInst::CreateBitOrPointerCast(NewOp, DestTy);
   }
 
+  // Similarly, if one operand is zexted and the other is a constant, move the
+  // logic operation ahead of the zext if the constant is unchanged in the
+  // smaller source type. Performing the logic in a smaller type may provide
+  // more information to later folds, and the smaller logic instruction may be
+  // cheaper (particularly in the case of vectors).
+  Value *X;
+  if (match(Op0, m_OneUse(m_ZExt(m_Value(X)))) && match(Op1, m_Constant(C))) {
+    Constant *TruncC = ConstantExpr::getTrunc(C, SrcTy);
+    Constant *ZextTruncC = ConstantExpr::getZExt(TruncC, DestTy);
+    if (ZextTruncC == C) {
+      // LogicOpc (zext X), C --> zext (LogicOpc X, C)
+      Value *NewOp = Builder->CreateBinOp(LogicOpc, X, TruncC);
+      return new ZExtInst(NewOp, DestTy);
+    }
+  }
+
   CastInst *Cast1 = dyn_cast<CastInst>(Op1);
   if (!Cast1)
     return nullptr;