From d8295c188946b0f07d62420c2f08c940f70b03ac Mon Sep 17 00:00:00 2001
From: Andrew Kelley <superjoe30@gmail.com>
Date: Sat, 7 Jul 2018 00:25:32 -0400
Subject: add @popCount intrinsic

---
 src/bigint.cpp | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

(limited to 'src/bigint.cpp')

diff --git a/src/bigint.cpp b/src/bigint.cpp
index bb227a7c3d..bf18b9a1bf 100644
--- a/src/bigint.cpp
+++ b/src/bigint.cpp
@@ -1593,6 +1593,37 @@ void bigint_append_buf(Buf *buf, const BigInt *op, uint64_t base) {
     }
 }
 
+size_t bigint_popcount_unsigned(const BigInt *bi) {
+    assert(!bi->is_negative);
+    if (bi->digit_count == 0)
+        return 0;
+
+    size_t count = 0;
+    size_t bit_count = bi->digit_count * 64;
+    for (size_t i = 0; i < bit_count; i += 1) {
+        if (bit_at_index(bi, i))
+            count += 1;
+    }
+    return count;
+}
+
+size_t bigint_popcount_signed(const BigInt *bi, size_t bit_count) {
+    if (bit_count == 0)
+        return 0;
+    if (bi->digit_count == 0)
+        return 0;
+
+    BigInt twos_comp = {0};
+    to_twos_complement(&twos_comp, bi, bit_count);
+
+    size_t count = 0;
+    for (size_t i = 0; i < bit_count; i += 1) {
+        if (bit_at_index(&twos_comp, i))
+            count += 1;
+    }
+    return count;
+}
+
 size_t bigint_ctz(const BigInt *bi, size_t bit_count) {
     if (bit_count == 0)
         return 0;
-- 
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