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

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

1 files changed, 32 insertions, 0 deletions

diff --git a/llvm/unittests/ADT/APIntTest.cpp b/llvm/unittests/ADT/APIntTest.cpp
index 4eb6d676b8c..48f91195e44 100644
--- a/llvm/unittests/ADT/APIntTest.cpp
+++ b/llvm/unittests/ADT/APIntTest.cpp
@@ -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));