[libc-commits] [libc] [libc] Allow BigInt class to use base word types other than uint64_t. (PR #81634)

[via libc-commits]

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@@ -254,33 +258,33 @@ template <size_t Bits, bool Signed> struct BigInt {
     return partial_sum.val[1];
   }
 
-  LIBC_INLINE constexpr BigInt<Bits, Signed>
-  operator*(const BigInt<Bits, Signed> &other) const {
+  LIBC_INLINE constexpr BigInt<Bits, Signed, WordType>
+  operator*(const BigInt<Bits, Signed, WordType> &other) const {
     if constexpr (Signed) {
-      BigInt<Bits, false> a(*this);
-      BigInt<Bits, false> b(other);
-      bool a_neg = (a.val[WORDCOUNT - 1] >> 63);
-      bool b_neg = (b.val[WORDCOUNT - 1] >> 63);
+      BigInt<Bits, false, WordType> a(*this);
+      BigInt<Bits, false, WordType> b(other);
+      bool a_neg = (a.val[WORD_COUNT - 1] >> (WORD_SIZE - 1));
+      bool b_neg = (b.val[WORD_COUNT - 1] >> (WORD_SIZE - 1));
       if (a_neg)
         a = -a;
       if (b_neg)
         b = -b;
-      BigInt<Bits, false> prod = a * b;
+      BigInt<Bits, false, WordType> prod = a * b;
       if (a_neg != b_neg)
         prod = -prod;
-      return static_cast<BigInt<Bits, true>>(prod);
+      return static_cast<BigInt<Bits, true, WordType>>(prod);
     } else {
 
-      if constexpr (WORDCOUNT == 1) {
+      if constexpr (WORD_COUNT == 1) {
         return {val[0] * other.val[0]};
       } else {
-        BigInt<Bits, Signed> result(0);
-        BigInt<128, Signed> partial_sum(0);
-        uint64_t carry = 0;
-        for (size_t i = 0; i < WORDCOUNT; ++i) {
+        BigInt<Bits, Signed, WordType> result(0);
+        BigInt<2 * WORD_SIZE, Signed, WordType> partial_sum(0);
+        WordType carry = 0;
+        for (size_t i = 0; i < WORD_COUNT; ++i) {
           for (size_t j = 0; j <= i; j++) {
-            NumberPair<uint64_t> prod = full_mul(val[j], other.val[i - j]);
-            BigInt<128, Signed> tmp({prod.lo, prod.hi});
+            NumberPair<WordType> prod = full_mul(val[j], other.val[i - j]);
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michaelrj-google wrote:

full_mull can only handle sizes up to uint64. Should we add a check?

https://github.com/llvm/llvm-project/pull/81634