From bffb6bdf455097ac5a6f98eb4bb549166e318989 Mon Sep 17 00:00:00 2001
From: Benoit Steiner <benoit.steiner.goog@gmail.com>
Date: Wed, 25 Feb 2015 23:54:43 -0800
Subject: Made TensorIntDiv.h compile with MSVC

---
 unsupported/Eigen/CXX11/src/Tensor/TensorIntDiv.h | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

(limited to 'unsupported/Eigen/CXX11/src/Tensor/TensorIntDiv.h')

diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorIntDiv.h b/unsupported/Eigen/CXX11/src/Tensor/TensorIntDiv.h
index 4b22c64de..535abd6fd 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorIntDiv.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorIntDiv.h
@@ -29,14 +29,16 @@ namespace Eigen {
 namespace internal {
 
 namespace {
+  // Note: result is undefined if val == 0
   template <typename T>
   EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE int count_leading_zeros(const T val)
   {
 #ifndef __CUDA_ARCH__
-    if (sizeof(T) == 8) {
-      return __builtin_clzl(val);
-    }
-    return __builtin_clz(val);
+    return __builtin_clz(static_cast<uint32_t>(val));
+#elif EIGEN_COMP_MSVC
+    DWORD leading_zero = 0;
+    _BitScanReverse( &leading_zero, value);
+    return 31 - leading_zero;
 #else
     return __clz(val);
 #endif
-- 
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