Add a getNumSignBits() method to APInt.

llvm-svn: 126379

2 files changed, 7 insertions, 6 deletions

diff --git a/llvm/include/llvm/ADT/APInt.h b/llvm/include/llvm/ADT/APInt.h
index b91d5dc9bcf..d1fd3e5034b 100644
--- a/llvm/include/llvm/ADT/APInt.h
+++ b/llvm/include/llvm/ADT/APInt.h
@@ -1193,6 +1193,12 @@ public:
   /// @brief Count the number of leading one bits.
   unsigned countLeadingOnes() const;
 
+  /// Computes the number of leading bits of this APInt that are equal to its
+  /// sign bit.
+  unsigned getNumSignBits() const {
+    return isNegative() ? countLeadingOnes() : countLeadingZeros();
+  }
+
   /// countTrailingZeros - This function is an APInt version of the
   /// countTrailingZeros_{32,64} functions in MathExtras.h. It counts
   /// the number of zeros from the least significant bit to the first set bit.
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 2fb2f2d8aa1..0b7cbcc47e1 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -2088,12 +2088,7 @@ unsigned SelectionDAG::ComputeNumSignBits(SDValue Op, unsigned Depth) const{
 
   case ISD::Constant: {
     const APInt &Val = cast<ConstantSDNode>(Op)->getAPIntValue();
-    // If negative, return # leading ones.
-    if (Val.isNegative())
-      return Val.countLeadingOnes();
-
-    // Return # leading zeros.
-    return Val.countLeadingZeros();
+    return Val.getNumSignBits();
   }
 
   case ISD::SIGN_EXTEND: