From 60d9df11c172ecb040ce5ba08087ee4c3fd8e9e6 Mon Sep 17 00:00:00 2001
From: Benoit Steiner <benoit.steiner.goog@gmail.com>
Date: Fri, 4 Mar 2016 16:27:02 -0800
Subject: [PATCH] Fixed the computation of leading zeros when compiling with
 msvc.

---
 unsupported/Eigen/CXX11/src/Tensor/TensorIntDiv.h | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorIntDiv.h b/unsupported/Eigen/CXX11/src/Tensor/TensorIntDiv.h
index 78d6da28a..75567f1ff 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorIntDiv.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorIntDiv.h
@@ -36,14 +36,7 @@ namespace {
 #ifdef __CUDA_ARCH__
     return (sizeof(T) == 8) ? __clzll(val) : __clz(val);
 #elif EIGEN_COMP_MSVC
-    DWORD leading_zeros = 0;
-    if (sizeof(T) == 8) {
-      _BitScanReverse64(&leading_zeros, val);
-    }
-    else {
-      _BitScanReverse(&leading_zeros, val);
-    }
-    return leading_zeros;
+    return (sizeof(T) == 8) ? __lzcnt64(val) : __lzcnt(val);
 #else
     EIGEN_STATIC_ASSERT(sizeof(unsigned long long) == 8, YOU_MADE_A_PROGRAMMING_MISTAKE);
     return (sizeof(T) == 8) ?