[NFC][DAGCombine] Clarify comment for 'A - (A & (B - 1))' fold

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 5dbe29f..cd6d33f 100644 (file)
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3104,7 +3104,7 @@ SDValue DAGCombiner::visitSUB(SDNode *N) {
                        DAG.getNode(ISD::SUB, DL, VT, N1.getOperand(1),
                                    N1.getOperand(0)));
 
-  // A - (A & (B - 1))  ->  A & (0 - B)
+  // A - (A & (B - 1))  ->  A & (~(B - 1))  ->  A & (0 - B)
   if (N1.getOpcode() == ISD::AND && N1.hasOneUse()) {
     SDValue A = N1.getOperand(0);
     SDValue BDec = N1.getOperand(1);