[llvm] r313908 - [DAGCombiner] Slightly simplify some code by using APInt::isMask() and countTrailingOnes instead of getting active bits and checking if all the bits below that make a mask.

[Craig Topper via llvm-commits]

Author: ctopper
Date: Thu Sep 21 13:12:19 2017
New Revision: 313908

URL: http://llvm.org/viewvc/llvm-project?rev=313908&view=rev
Log:
[DAGCombiner] Slightly simplify some code by using APInt::isMask() and countTrailingOnes instead of getting active bits and checking if all the bits below that make a mask.

At least for the 64-bit and less case, we should be able to determine if we even have a mask without counting any bits. This also removes the need to explicitly check for 0 active bits, isMask will return false for 0.

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

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=313908&r1=313907&r2=313908&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Thu Sep 21 13:12:19 2017
@@ -3666,11 +3666,11 @@ SDValue DAGCombiner::visitANDLike(SDValu
 bool DAGCombiner::isAndLoadExtLoad(ConstantSDNode *AndC, LoadSDNode *LoadN,
                                    EVT LoadResultTy, EVT &ExtVT, EVT &LoadedVT,
                                    bool &NarrowLoad) {
-  uint32_t ActiveBits = AndC->getAPIntValue().getActiveBits();
-
-  if (ActiveBits == 0 || !AndC->getAPIntValue().isMask(ActiveBits))
+  if (!AndC->getAPIntValue().isMask())
     return false;
 
+  unsigned ActiveBits = AndC->getAPIntValue().countTrailingOnes();
+
   ExtVT = EVT::getIntegerVT(*DAG.getContext(), ActiveBits);
   LoadedVT = LoadN->getMemoryVT();