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

[Nick Desaulniers via libc-commits]

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@@ -112,76 +355,67 @@ struct BigInt {
   template <size_t OtherBits, bool OtherSigned>
   LIBC_INLINE constexpr BigInt(
       const BigInt<OtherBits, OtherSigned, WordType> &other) {
-    if (OtherBits >= Bits) {
+    if (OtherBits >= Bits) { // truncate
       for (size_t i = 0; i < WORD_COUNT; ++i)
         val[i] = other[i];
-    } else {
+    } else { // zero or sign extend
       size_t i = 0;
       for (; i < OtherBits / WORD_SIZE; ++i)
         val[i] = other[i];
-      WordType sign = 0;
-      if constexpr (Signed && OtherSigned) {
-        sign = static_cast<WordType>(
-            -static_cast<cpp::make_signed_t<WordType>>(other.is_neg()));
-      }
-      for (; i < WORD_COUNT; ++i)
-        val[i] = sign;
+      extend(i, Signed && other.is_neg());
     }
   }
 
   // Construct a BigInt from a C array.
-  template <size_t N, cpp::enable_if_t<N <= WORD_COUNT, int> = 0>
-  LIBC_INLINE constexpr BigInt(const WordType (&nums)[N]) {
-    size_t min_wordcount = N < WORD_COUNT ? N : WORD_COUNT;
-    size_t i = 0;
-    for (; i < min_wordcount; ++i)
+  template <size_t N> LIBC_INLINE constexpr BigInt(const WordType (&nums)[N]) {
+    static_assert(N == WORD_COUNT);
+    for (size_t i = 0; i < WORD_COUNT; ++i)
       val[i] = nums[i];
+  }
 
-    // If nums doesn't completely fill val, then fill the rest with zeroes.
-    for (; i < WORD_COUNT; ++i)
-      val[i] = 0;
+  LIBC_INLINE constexpr explicit BigInt(
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nickdesaulniers wrote:

Is the `explicit` keyword necessary here when there's more than 1 parameter?

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