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[APIntTest] multiplicativeInverse(): clarify test 

Clarify that multiplicative inverse exists for all odd numbers,
and does not exist for all even numbers (including 0).

llvm-svn: 364920
This commit is contained in:
Roman Lebedev 2019-07-02 13:21:17 +00:00
parent ca4e80182e
commit 1a5ebe1fb1
1 changed files with 7 additions and 4 deletions
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11
llvm/unittests/ADT/APIntTest.cpp
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@ -2527,10 +2527,13 @@ TEST(APIntTest, MultiplicativeInverseExaustive) {
.multiplicativeInverse(APInt::getSignedMinValue(BitWidth + 1))
.trunc(BitWidth);
APInt One = V * MulInv;
EXPECT_TRUE(MulInv.isNullValue() || One.isOneValue())
<< " bitwidth = " << BitWidth << ", value = " << Value
<< ", computed multiplicative inverse = " << MulInv
<< ", value * multiplicative inverse = " << One << " (should be 1)";
if (!V.isNullValue() && V.countTrailingZeros() == 0) {
// Multiplicative inverse exists for all odd numbers.
EXPECT_TRUE(One.isOneValue());
} else {
// Multiplicative inverse does not exist for even numbers (and 0).
EXPECT_TRUE(MulInv.isNullValue());
}
}
}
}