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APInt: Add overload of isMask

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

llvm-svn: 266101
This commit is contained in:
Matt Arsenault 2016-04-12 18:17:23 +00:00
parent 9e606d4f83
commit 795072118d
2 changed files with 24 additions and 0 deletions
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7
include/llvm/ADT/APInt.h
View File

@ -1782,6 +1782,13 @@ inline bool isMask(unsigned numBits, const APInt &APIVal) {
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) {

17
unittests/ADT/APIntTest.cpp
View File

@ -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