Index: include/algorithm
===================================================================
--- include/algorithm
+++ include/algorithm
@@ -797,7 +797,7 @@
   unsigned long where;
   // Search from LSB to MSB for first set bit.
   // Returns zero if no set bit is found.
-  if (_BitScanForward(&where, mask))
+  if (_BitScanForward(&where, __x))
     return where;
   return 32;
 #endif
@@ -823,15 +823,15 @@
 // Returns zero if no set bit is found.
 #if defined(_LIBCPP_HAS_BITSCAN64)
     (defined(_M_AMD64) || defined(__x86_64__))
-  if (_BitScanForward64(&where, mask))
+  if (_BitScanForward64(&where, __x))
     return static_cast<int>(where);
 #else
   // Win32 doesn't have _BitScanForward64 so emulate it with two 32 bit calls.
   // Scan the Low Word.
-  if (_BitScanForward(&where, static_cast<unsigned long>(mask)))
+  if (_BitScanForward(&where, static_cast<unsigned long>(__x)))
     return where;
   // Scan the High Word.
-  if (_BitScanForward(&where, static_cast<unsigned long>(mask >> 32)))
+  if (_BitScanForward(&where, static_cast<unsigned long>(__x >> 32)))
     return where + 32; // Create a bit offset from the LSB.
 #endif
   return 64;
@@ -849,7 +849,7 @@
   unsigned long where;
   // Search from LSB to MSB for first set bit.
   // Returns zero if no set bit is found.
-  if (_BitScanReverse(&where, mask))
+  if (_BitScanReverse(&where, __x))
     return 31 - where;
   return 32; // Undefined Behavior.
 #endif
@@ -874,14 +874,14 @@
 // BitScanReverse scans from MSB to LSB for first set bit.
 // Returns 0 if no set bit is found.
 #if defined(_LIBCPP_HAS_BITSCAN64)
-  if (_BitScanReverse64(&where, mask))
+  if (_BitScanReverse64(&where, __x))
     return static_cast<int>(63 - where);
 #else
   // Scan the high 32 bits.
-  if (_BitScanReverse(&where, static_cast<unsigned long>(mask >> 32)))
+  if (_BitScanReverse(&where, static_cast<unsigned long>(__x >> 32)))
     return 63 - (where + 32); // Create a bit offset from the MSB.
   // Scan the low 32 bits.
-  if (_BitScanReverse(&where, static_cast<unsigned long>(mask)))
+  if (_BitScanReverse(&where, static_cast<unsigned long>(__x)))
     return 63 - where;
 #endif
   return 64; // Undefined Behavior.