[libc] [llvm] [libc] Refactor `BigInt` (PR #86137)

[via llvm-commits]

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@@ -244,18 +244,30 @@ LIBC_INLINE constexpr bool is_negative(cpp::array<word, N> &array) {
 enum Direction { LEFT, RIGHT };
 
 // A bitwise shift on an array of elements.
+// TODO: Make the result UB when 'offset' is greater or equal to the number of
+// bits in 'array'. This will allow for better code performance.
 template <Direction direction, bool is_signed, typename word, size_t N>
-LIBC_INLINE constexpr void shift(cpp::array<word, N> &array, size_t offset) {
+LIBC_INLINE constexpr cpp::array<word, N> shift(cpp::array<word, N> array,
+                                                size_t offset) {
   constexpr size_t WORD_BITS = cpp::numeric_limits<word>::digits;
   constexpr size_t TOTAL_BITS = N * WORD_BITS;
   if (offset == 0)
-    return;
-  if (offset >= TOTAL_BITS) {
-    array = {};
-    return;
+    return array;
+  if (offset >= TOTAL_BITS)
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lntue wrote:

Use `LIBC_UNLIKELY` to provide hints for these two exceptional cases?

https://github.com/llvm/llvm-project/pull/86137