[llvm] r266101 - APInt: Add overload of isMask

[Matt Arsenault via llvm-commits]

Author: arsenm
Date: Tue Apr 12 13:17:23 2016
New Revision: 266101

URL: http://llvm.org/viewvc/llvm-project?rev=266101&view=rev
Log:
APInt: Add overload of isMask

This mimics the version in MathExtras.h which isn't testing for a
specific mask size.

Modified:
    llvm/trunk/include/llvm/ADT/APInt.h
    llvm/trunk/unittests/ADT/APIntTest.cpp

Modified: llvm/trunk/include/llvm/ADT/APInt.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/APInt.h?rev=266101&r1=266100&r2=266101&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ADT/APInt.h (original)
+++ llvm/trunk/include/llvm/ADT/APInt.h Tue Apr 12 13:17:23 2016
@@ -1782,6 +1782,13 @@ inline bool isMask(unsigned numBits, con
          APIVal == APInt::getLowBitsSet(APIVal.getBitWidth(), numBits);
 }
 
+/// \returns true if the argument is a non-empty sequence of ones starting at
+/// the least significant bit with the remainder zero (32 bit version).
+/// Ex. isMask(0x0000FFFFU) == true.
+inline bool isMask(const APInt &Value) {
+  return (Value != 0) && ((Value + 1) & Value) == 0;
+}
+
 /// \brief Return true if the argument APInt value contains a sequence of ones
 /// with the remainder zero.
 inline bool isShiftedMask(unsigned numBits, const APInt &APIVal) {

Modified: llvm/trunk/unittests/ADT/APIntTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/ADT/APIntTest.cpp?rev=266101&r1=266100&r2=266101&view=diff
==============================================================================
--- llvm/trunk/unittests/ADT/APIntTest.cpp (original)
+++ llvm/trunk/unittests/ADT/APIntTest.cpp Tue Apr 12 13:17:23 2016
@@ -994,6 +994,23 @@ TEST(APIntTest, IsSplat) {
   EXPECT_TRUE(E.isSplat(32));
 }
 
+TEST(APIntTest, isMask) {
+  EXPECT_FALSE(APIntOps::isMask(APInt(32, 0x01010101)));
+  EXPECT_FALSE(APIntOps::isMask(APInt(32, 0xf0000000)));
+  EXPECT_FALSE(APIntOps::isMask(APInt(32, 0xffff0000)));
+  EXPECT_FALSE(APIntOps::isMask(APInt(32, 0xff << 1)));
+
+  for (int N : { 1, 2, 3, 4, 7, 8, 16, 32, 64, 127, 128, 129, 256 }) {
+    EXPECT_FALSE(APIntOps::isMask(APInt(N, 0)));
+
+    APInt One(N, 1);
+    for (int I = 1; I <= N; ++I) {
+      APInt MaskVal = One.shl(I) - 1;
+      EXPECT_TRUE(APIntOps::isMask(MaskVal));
+    }
+  }
+}
+
 #if defined(__clang__)
 // Disable the pragma warning from versions of Clang without -Wself-move
 #pragma clang diagnostic push