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[APInt] Add unittests that demonstrate how very broken APIntOps::isShiftedMask is.

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Did you know that 0 is a shifted mask? But 0x0000ff00 and 0x000000ff aren't? At least we get 0xff000000 right.

I only see one usage of this function in the code base today and its in InstCombine. I think its protected against 0 being misreported as a mask. I guess we just don't have tests for the missed cases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@299187 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Craig Topper 2017-03-31 06:30:25 +00:00
parent 1fcb6de3bd
commit dbf64c9e97
1 changed files with 25 additions and 0 deletions
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25
unittests/ADT/APIntTest.cpp
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@ -1575,6 +1575,31 @@ TEST(APIntTest, isMask) {
}
}
TEST(APIntTest, isShiftedMask) {
EXPECT_FALSE(APIntOps::isShiftedMask(32, APInt(32, 0x01010101)));
EXPECT_TRUE(APIntOps::isShiftedMask(32, APInt(32, 0xf0000000)));
EXPECT_TRUE(APIntOps::isShiftedMask(32, APInt(32, 0xffff0000)));
EXPECT_FALSE(APIntOps::isShiftedMask(32, APInt(32, 0xff << 1))); // BUG
for (int N : { 1, 2, 3, 4, 7, 8, 16, 32, 64, 127, 128, 129, 256 }) {
EXPECT_TRUE(APIntOps::isShiftedMask(N, APInt(N, 0))); // BUG
APInt One(N, 1);
for (int I = 1; I < N; ++I) {
APInt MaskVal = One.shl(I) - 1;
EXPECT_FALSE(APIntOps::isShiftedMask(N, MaskVal)); // BUG
}
for (int I = 1; I < N - 1; ++I) {
APInt MaskVal = One.shl(I);
EXPECT_FALSE(APIntOps::isShiftedMask(N, MaskVal)); // BUG
}
for (int I = 1; I < N; ++I) {
APInt MaskVal = APInt::getHighBitsSet(N, I);
EXPECT_TRUE(APIntOps::isShiftedMask(N, MaskVal));
}
}
}
#if defined(__clang__)
// Disable the pragma warning from versions of Clang without -Wself-move
#pragma clang diagnostic push