[llvm] 1711be7 - [NFC][DAGCombine] Clarify comment for 'A - (A & (B - 1))' fold

[Roman Lebedev via llvm-commits]

Author: Roman Lebedev
Date: 2020-01-03T17:55:42+03:00
New Revision: 1711be78f74064d563b165f20debd769929eca06

URL: https://github.com/llvm/llvm-project/commit/1711be78f74064d563b165f20debd769929eca06
DIFF: https://github.com/llvm/llvm-project/commit/1711be78f74064d563b165f20debd769929eca06.diff

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

Added: 
    

Modified: 
    llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

Removed: 
    


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diff  --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 5dbe29f5fbdb..cd6d33ffa9e7 100644
--- 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);