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[APInt] Keep the original bit width in quotient and remainder

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Some trivial cases in udivrem were handled by directly assigning 0 or 1
to APInt objects. This would set the bit width to 1, instead of the bit
width of the inputs. A potentially undesirable side effect of that is
that with the bit width of 1, 1 equals -1.

Differential Revision: https://reviews.llvm.org/D49554

llvm-svn: 337478
This commit is contained in:
Krzysztof Parzyszek 2018-07-19 18:07:56 +00:00
parent 53d54bbc8f
commit 5d9659bfb9
2 changed files with 49 additions and 16 deletions
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33
lib/Support/APInt.cpp
View File

@ -1735,25 +1735,25 @@ void APInt::udivrem(const APInt &LHS, const APInt &RHS,
// Check the degenerate cases
if (lhsWords == 0) {
Quotient = 0; // 0 / Y ===> 0
Remainder = 0; // 0 % Y ===> 0
Quotient = APInt(BitWidth, 0); // 0 / Y ===> 0
Remainder = APInt(BitWidth, 0); // 0 % Y ===> 0
return;
}
if (rhsBits == 1) {
Quotient = LHS; // X / 1 ===> X
Remainder = 0; // X % 1 ===> 0
Quotient = LHS; // X / 1 ===> X
Remainder = APInt(BitWidth, 0); // X % 1 ===> 0
}
if (lhsWords < rhsWords || LHS.ult(RHS)) {
Remainder = LHS; // X % Y ===> X, iff X < Y
Quotient = 0; // X / Y ===> 0, iff X < Y
Remainder = LHS; // X % Y ===> X, iff X < Y
Quotient = APInt(BitWidth, 0); // X / Y ===> 0, iff X < Y
return;
}
if (LHS == RHS) {
Quotient = 1; // X / X ===> 1
Remainder = 0; // X % X ===> 0;
Quotient = APInt(BitWidth, 1); // X / X ===> 1
Remainder = APInt(BitWidth, 0); // X % X ===> 0;
return;
}
@ -1801,25 +1801,26 @@ void APInt::udivrem(const APInt &LHS, uint64_t RHS, APInt &Quotient,
// Check the degenerate cases
if (lhsWords == 0) {
Quotient = 0; // 0 / Y ===> 0
Remainder = 0; // 0 % Y ===> 0
Quotient = APInt(BitWidth, 0); // 0 / Y ===> 0
Remainder = 0; // 0 % Y ===> 0
return;
}
if (RHS == 1) {
Quotient = LHS; // X / 1 ===> X
Remainder = 0; // X % 1 ===> 0
Quotient = LHS; // X / 1 ===> X
Remainder = 0; // X % 1 ===> 0
return;
}
if (LHS.ult(RHS)) {
Remainder = LHS.getZExtValue(); // X % Y ===> X, iff X < Y
Quotient = 0; // X / Y ===> 0, iff X < Y
Remainder = LHS.getZExtValue(); // X % Y ===> X, iff X < Y
Quotient = APInt(BitWidth, 0); // X / Y ===> 0, iff X < Y
return;
}
if (LHS == RHS) {
Quotient = 1; // X / X ===> 1
Remainder = 0; // X % X ===> 0;
Quotient = APInt(BitWidth, 1); // X / X ===> 1
Remainder = 0; // X % X ===> 0;
return;
}

32
unittests/ADT/APIntTest.cpp
View File

@ -1060,6 +1060,38 @@ TEST(APIntTest, divremuint) {
APInt{1024, 1});
}
TEST(APIntTest, divrem_simple) {
// Test simple cases.
APInt A(65, 2), B(65, 2);
APInt Q, R;
// X / X
APInt::sdivrem(A, B, Q, R);
EXPECT_EQ(Q, APInt(65, 1));
EXPECT_EQ(R, APInt(65, 0));
APInt::udivrem(A, B, Q, R);
EXPECT_EQ(Q, APInt(65, 1));
EXPECT_EQ(R, APInt(65, 0));
// 0 / X
APInt O(65, 0);
APInt::sdivrem(O, B, Q, R);
EXPECT_EQ(Q, APInt(65, 0));
EXPECT_EQ(R, APInt(65, 0));
APInt::udivrem(O, B, Q, R);
EXPECT_EQ(Q, APInt(65, 0));
EXPECT_EQ(R, APInt(65, 0));
// X / 1
APInt I(65, 1);
APInt::sdivrem(A, I, Q, R);
EXPECT_EQ(Q, A);
EXPECT_EQ(R, APInt(65, 0));
APInt::udivrem(A, I, Q, R);
EXPECT_EQ(Q, A);
EXPECT_EQ(R, APInt(65, 0));
}
TEST(APIntTest, fromString) {
EXPECT_EQ(APInt(32, 0), APInt(32, "0", 2));
EXPECT_EQ(APInt(32, 1), APInt(32, "1", 2));