From cc1daf3a05929148239cebf8a9f2452785e20a2c Mon Sep 17 00:00:00 2001
From: Guilherme Amadio <amadio@cern.ch>
Date: Fri, 6 Mar 2020 10:46:02 +0100
Subject: [PATCH] Avoid redefinition of _bit_scan_{forward,reverse} macros

Fixes #247.
---
 Vc/common/bitscanintrinsics.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Vc/common/bitscanintrinsics.h b/Vc/common/bitscanintrinsics.h
index 625435638..612eee3a7 100644
--- a/Vc/common/bitscanintrinsics.h
+++ b/Vc/common/bitscanintrinsics.h
@@ -32,7 +32,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #  if Vc_GCC >= 0x40500
      // GCC 4.5.0 introduced _bit_scan_forward / _bit_scan_reverse
 #    include <x86intrin.h>
-#  else
+#  elif !defined(_bit_scan_forward)
      // GCC <= 4.4 and clang have x86intrin.h, but not the required functions
 #    define _bit_scan_forward(x) __builtin_ctz(x)
 #include "macros.h"