From 5ba4194586f3b0e892596386e87a525a2635c43b Mon Sep 17 00:00:00 2001
From: "Jurjen N. E. Bos" <jneb@users.noreply.github.com>
Date: Fri, 18 Dec 2020 17:58:24 +0100
Subject: [PATCH] Use 64 bit bsr

I am determined to get this to work!
---
 Include/internal/pycore_bitutils.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/Include/internal/pycore_bitutils.h b/Include/internal/pycore_bitutils.h
index 0f87160b4e3..21eb6c62bee 100644
--- a/Include/internal/pycore_bitutils.h
+++ b/Include/internal/pycore_bitutils.h
@@ -186,9 +186,12 @@ _Py_bit_length_size_t(size_t x)
     }
 #elif defined(_MSC_VER)
     // _BitScanReverse() is documented to search 32 bits.
-    Py_BUILD_ASSERT(sizeof(size_t) <= 4);
-    unsigned long msb;
+    size_t msb;
+#if SIZEOF_SIZE_T == 8
+    if (_BitScanReverse64(&msb, x)) {
+#else
     if (_BitScanReverse(&msb, x)) {
+#endif
         return (int)msb + 1;
     }
     else {