From 331a0dc8d866f95424d7f2519702305b783c29fb Mon Sep 17 00:00:00 2001
From: Nicola Cabiddu <nicola.cabiddu@mongodb.com>
Date: Tue, 5 Mar 2024 15:23:51 +0000
Subject: [PATCH] please windows builder warnings + x86

---
 src/realm/array_direct.hpp | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/src/realm/array_direct.hpp b/src/realm/array_direct.hpp
index ab011903627..03c70d324a7 100644
--- a/src/realm/array_direct.hpp
+++ b/src/realm/array_direct.hpp
@@ -23,6 +23,9 @@
 #include <realm/utilities.hpp>
 #include <realm/alloc.hpp>
 #include <realm/array_encode.hpp>
+#ifdef __WIN32
+#include <stdint.h>
+#endif
 
 // clang-format off
 /* wid == 16/32 likely when accessing offsets in B tree */
@@ -795,13 +798,28 @@ constexpr uint32_t inverse_width[65] = {
     65536 * 64 / 61, 65536 * 64 / 62, 65536 * 64 / 63, 65536 * 64 / 64,
 };
 
-inline int first_field_marked(int width, uint64_t vector)
+inline int countr_zero(uint64_t vector)
 {
-#if REALM_WINDOWS
-    int lz = (int)_tzcnt_u64(vector); // TODO: not clear if this is ok on all platforms
+    unsigned long where;
+#if defined(_WIN64)
+    if (_BitScanForward64(&where, vector))
+        return static_cast<int>(where);
+    return 64;
+#elif defined(_WIN32)
+    if (_BitScanForward(&where, static_cast<unsigned long>(vector)))
+        return static_cast<int>(where);
+    if (_BitScanForward(&where, static_cast<unsigned long>(vector >> 32)))
+        return static_cast<int>(where + 32);
+    return 32;
 #else
-    int lz = __builtin_ctzll(vector);
+    where = __builtin_ctzll(vector);
+    return static_cast<int>(where);
 #endif
+}
+
+inline int first_field_marked(int width, uint64_t vector)
+{
+    const auto lz = countr_zero(vector);
     int field = (lz * inverse_width[width]) >> 22;
     REALM_ASSERT_DEBUG(field == (lz / width));
     return field;