From ff2e5c3efe931e6a088c2368b0ce5d5c21f03c65 Mon Sep 17 00:00:00 2001
From: gingerBill <bill@gingerbill.org>
Date: Sun, 11 Jul 2021 17:43:56 +0100
Subject: Simplify `big_int_not` for negative inputs

---
 src/big_int.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

(limited to 'src/big_int.cpp')

diff --git a/src/big_int.cpp b/src/big_int.cpp
index 231064bea..9cb1ec586 100644
--- a/src/big_int.cpp
+++ b/src/big_int.cpp
@@ -415,6 +415,14 @@ void big_int_not(BigInt *dst, BigInt const *x, i32 bit_count, bool is_signed) {
 		big_int_from_u64(dst, 0);
 		return;
 	}
+	if (big_int_is_neg(x)) {
+		// ~x == -x - 1
+		big_int_neg(dst, x);
+		mp_decr(dst);
+		mp_mod_2d(dst, bit_count, dst);
+		return;
+	}
+
 
 	BigInt pow2b = {};
 	mp_2expt(&pow2b, bit_count);
-- 
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