From: Christopher Dykes <cdykes@fb.com>
Date: Wed, 4 May 2016 17:28:49 +0000 (-0700)
Subject: Implement __builtin_ctzll for MSVC
X-Git-Tag: 2016.07.26~282
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=f79d6393cfd203d7293ac634328e36a7673c34e9;p=folly.git

Implement __builtin_ctzll for MSVC

Summary: MSVC doesn't have it, but Folly uses it, so implement it in the Builtins portability header.

Reviewed By: yfeldblum

Differential Revision: D3256123

fb-gh-sync-id: fd9ea1b6098d97cf1fde4732905bae9bde8cd8ad
fbshipit-source-id: fd9ea1b6098d97cf1fde4732905bae9bde8cd8ad
---

diff --git a/folly/portability/Builtins.h b/folly/portability/Builtins.h
index 959ce5c2..567ca6e9 100755
--- a/folly/portability/Builtins.h
+++ b/folly/portability/Builtins.h
@@ -35,6 +35,11 @@ FOLLY_ALWAYS_INLINE int __builtin_clzll(unsigned long long x) {
   return (int)(_BitScanReverse64(&index, x) ? 63 - index : 64);
 }
 
+FOLLY_ALWAYS_INLINE int __builtin_ctzll(unsigned long long x) {
+  unsigned long index;
+  return (int)(_BitScanForward64(&index, x) ? index : 64);
+}
+
 FOLLY_ALWAYS_INLINE int __builtin_ffs(int x) {
   unsigned long index;
   return (int)(_BitScanForward(&index, (unsigned long)x) ? index : 0);