AK: Make truncating UFixedBigInts constexpr

Also add some tests and shift tests while we're at it.
luteresa · Oct 23, 2022 · bf6d4a5 · bf6d4a5
1 parent 66d07a4
commit bf6d4a5
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Showing 2 changed files with 16 additions and 1 deletion.
diff --git a/AK/UFixedBigInt.h b/AK/UFixedBigInt.h
@@ -87,7 +87,7 @@ requires(sizeof(T) >= sizeof(u64) && IsUnsigned<T>) class UFixedBigInt {
  }
 
  template<Unsigned U>
- requires(sizeof(T) >= sizeof(U)) explicit operator U() const
+ requires(sizeof(T) >= sizeof(U)) constexpr explicit operator U() const
  {
  return static_cast<U>(m_low);
  }

diff --git a/Tests/AK/TestUFixedBigInt.cpp b/Tests/AK/TestUFixedBigInt.cpp
@@ -88,6 +88,21 @@ TEST_CASE(div_mod)
  }
 }
 
+TEST_CASE(shifts)
+{
+ u128 val { 0x1234ULL };
+ EXPECT_EQ(val << 1u, u128(0x2468ull));
+ EXPECT_EQ(val << 4u, u128(0x12340ull));
+ EXPECT_EQ(val << 64u, u128(0ull, 0x1234ull));
+}
+
+TEST_CASE(constexpr_truncae)
+{
+ static constexpr u256 wide = u256(u128 { 0x8a4b08d32f8b8e48ULL, 0x8459322f67b8e26dULL }, u128 { 0xeea82af4312d1931ULL, 0x654fb5cfe82dbd58ULL });
+ static constexpr u64 val = static_cast<u64>(wide);
+ EXPECT_EQ(val, 0x8a4b08d32f8b8e48ULL);
+}
+
 TEST_CASE(mod_hardcoded)
 {
  EXPECT_EQ(u256(u128 { 0x8a4b08d32f8b8e48ULL, 0x8459322f67b8e26dULL }, u128 { 0xeea82af4312d1931ULL, 0x654fb5cfe82dbd58ULL }) % u256(u128 { 0x40a58652868d5d66ULL, 0x81d674bf7d6d6861ULL }, u128 { 0xa8314900e6188a82ULL, 0xc273ca947237b4aaULL }), u256(u128 { 0x8a4b08d32f8b8e48ULL, 0x8459322f67b8e26dULL }, u128 { 0xeea82af4312d1931ULL, 0x654fb5cfe82dbd58ULL }));