[libc] Fix BigInt's operator %=

[mikhailramalho]

This patch fixes cases where we try to do var %= 1. Previously this operator was calling .div directly since it would perform the inplace division and return the remainder, however, as an early exit condition a division by one returns zero as the remainder. The remainder being returned by div was not being assigned to var.

[llvmbot]

@llvm/pr-subscribers-libc

Author: Mikhail R. Gadelha (mikhailramalho)

Changes

This patch fixes cases where we try to do var %= 1. Previously this operator was calling .div directly since it would perform the inplace division and return the remainder, however, as an early exit condition a division by one returns zero as the remainder. The remainder being returned by div was not being assigned to var.

---

Full diff: https://github.com/llvm/llvm-project/pull/98484.diff

1 Files Affected:

• (modified) libc/src/__support/big_int.h (+2-1)

diff --git a/libc/src/__support/big_int.h b/libc/src/__support/big_int.h
index 82a5251418854..8eeb4db9d650b 100644
--- a/libc/src/__support/big_int.h
+++ b/libc/src/__support/big_int.h
@@ -732,7 +732,8 @@ struct BigInt {
   }
 
   LIBC_INLINE constexpr BigInt operator%=(const BigInt &other) {
-    return *this->div(other);
+    *this = *this % other;
+    return *this;
   }
 
   LIBC_INLINE constexpr BigInt &operator*=(const BigInt &other) {