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[APInt] Introduce clearLowBits()

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Summary: Equivalent to `x & -2^K`.

Reviewers: RKSimon, craig.topper

Reviewed By: RKSimon, craig.topper

Subscribers: dexonsmith, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65369

llvm-svn: 367287
This commit is contained in:
Roman Lebedev 2019-07-30 07:09:41 +00:00
parent 968cd8a990
commit 57f50743c9
2 changed files with 72 additions and 0 deletions
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7
include/llvm/ADT/APInt.h
View File

@ -1467,6 +1467,13 @@ public:
U.pVal[whichWord(BitPosition)] &= Mask;
}
/// Set bottom loBits bits to 0.
void clearLowBits(unsigned loBits) {
assert(loBits <= BitWidth && "More bits than bitwidth");
APInt Keep = getHighBitsSet(BitWidth, BitWidth - loBits);
*this &= Keep;
}
/// Set the sign bit to 0.
void clearSignBit() {
clearBit(BitWidth - 1);

65
unittests/ADT/APIntTest.cpp
View File

@ -2117,6 +2117,71 @@ TEST(APIntTest, getHiBits) {
EXPECT_EQ(0xc, i128.getHiBits(4));
}
TEST(APIntTest, clearLowBits) {
APInt i64hi32 = APInt::getAllOnesValue(64);
i64hi32.clearLowBits(32);
EXPECT_EQ(32u, i64hi32.countLeadingOnes());
EXPECT_EQ(0u, i64hi32.countLeadingZeros());
EXPECT_EQ(64u, i64hi32.getActiveBits());
EXPECT_EQ(32u, i64hi32.countTrailingZeros());
EXPECT_EQ(0u, i64hi32.countTrailingOnes());
EXPECT_EQ(32u, i64hi32.countPopulation());
APInt i128hi64 = APInt::getAllOnesValue(128);
i128hi64.clearLowBits(64);
EXPECT_EQ(64u, i128hi64.countLeadingOnes());
EXPECT_EQ(0u, i128hi64.countLeadingZeros());
EXPECT_EQ(128u, i128hi64.getActiveBits());
EXPECT_EQ(64u, i128hi64.countTrailingZeros());
EXPECT_EQ(0u, i128hi64.countTrailingOnes());
EXPECT_EQ(64u, i128hi64.countPopulation());
APInt i128hi24 = APInt::getAllOnesValue(128);
i128hi24.clearLowBits(104);
EXPECT_EQ(24u, i128hi24.countLeadingOnes());
EXPECT_EQ(0u, i128hi24.countLeadingZeros());
EXPECT_EQ(128u, i128hi24.getActiveBits());
EXPECT_EQ(104u, i128hi24.countTrailingZeros());
EXPECT_EQ(0u, i128hi24.countTrailingOnes());
EXPECT_EQ(24u, i128hi24.countPopulation());
APInt i128hi104 = APInt::getAllOnesValue(128);
i128hi104.clearLowBits(24);
EXPECT_EQ(104u, i128hi104.countLeadingOnes());
EXPECT_EQ(0u, i128hi104.countLeadingZeros());
EXPECT_EQ(128u, i128hi104.getActiveBits());
EXPECT_EQ(24u, i128hi104.countTrailingZeros());
EXPECT_EQ(0u, i128hi104.countTrailingOnes());
EXPECT_EQ(104u, i128hi104.countPopulation());
APInt i128hi0 = APInt::getAllOnesValue(128);
i128hi0.clearLowBits(128);
EXPECT_EQ(0u, i128hi0.countLeadingOnes());
EXPECT_EQ(128u, i128hi0.countLeadingZeros());
EXPECT_EQ(0u, i128hi0.getActiveBits());
EXPECT_EQ(128u, i128hi0.countTrailingZeros());
EXPECT_EQ(0u, i128hi0.countTrailingOnes());
EXPECT_EQ(0u, i128hi0.countPopulation());
APInt i80hi1 = APInt::getAllOnesValue(80);
i80hi1.clearLowBits(79);
EXPECT_EQ(1u, i80hi1.countLeadingOnes());
EXPECT_EQ(0u, i80hi1.countLeadingZeros());
EXPECT_EQ(80u, i80hi1.getActiveBits());
EXPECT_EQ(79u, i80hi1.countTrailingZeros());
EXPECT_EQ(0u, i80hi1.countTrailingOnes());
EXPECT_EQ(1u, i80hi1.countPopulation());
APInt i32hi16 = APInt::getAllOnesValue(32);
i32hi16.clearLowBits(16);
EXPECT_EQ(16u, i32hi16.countLeadingOnes());
EXPECT_EQ(0u, i32hi16.countLeadingZeros());
EXPECT_EQ(32u, i32hi16.getActiveBits());
EXPECT_EQ(16u, i32hi16.countTrailingZeros());
EXPECT_EQ(0u, i32hi16.countTrailingOnes());
EXPECT_EQ(16u, i32hi16.countPopulation());
}
TEST(APIntTest, GCD) {
using APIntOps::GreatestCommonDivisor;