Revert "Establish the <bit> header. NFC yet. Reviewed as https://reviews.llvm.org/D50815"

Breaks build on sanitizer bots.

This reverts commit r339943.

llvm-svn: 339971

1 files changed, 136 insertions, 1 deletions

diff --git a/libcxx/include/algorithm b/libcxx/include/algorithm
index 74a326dbf5e..90f1d246c63 100644
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -645,7 +645,13 @@ template <class BidirectionalIterator, class Compare>
 #include <functional>
 #include <iterator>
 #include <cstddef>
-#include <bit>
+
+#if defined(__IBMCPP__)
+#include "support/ibm/support.h"
+#endif
+#if defined(_LIBCPP_COMPILER_MSVC)
+#include <intrin.h>
+#endif
 
 #include <__debug>
 
@@ -782,6 +788,135 @@ struct __debug_less
 
 #endif  // _LIBCPP_DEBUG
 
+// Precondition:  __x != 0
+inline _LIBCPP_INLINE_VISIBILITY
+unsigned __ctz(unsigned __x) {
+#ifndef _LIBCPP_COMPILER_MSVC
+    return static_cast<unsigned>(__builtin_ctz(__x));
+#else
+  static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
+  static_assert(sizeof(unsigned long) == 4, "");
+  unsigned long where;
+  // Search from LSB to MSB for first set bit.
+  // Returns zero if no set bit is found.
+  if (_BitScanForward(&where, __x))
+    return where;
+  return 32;
+#endif
+}
+
+inline _LIBCPP_INLINE_VISIBILITY
+unsigned long __ctz(unsigned long __x) {
+#ifndef _LIBCPP_COMPILER_MSVC
+    return static_cast<unsigned long>(__builtin_ctzl(__x));
+#else
+    static_assert(sizeof(unsigned long) == sizeof(unsigned), "");
+    return __ctz(static_cast<unsigned>(__x));
+#endif
+}
+
+inline _LIBCPP_INLINE_VISIBILITY
+unsigned long long __ctz(unsigned long long __x) {
+#ifndef _LIBCPP_COMPILER_MSVC
+    return static_cast<unsigned long long>(__builtin_ctzll(__x));
+#else
+    unsigned long where;
+// Search from LSB to MSB for first set bit.
+// Returns zero if no set bit is found.
+#if defined(_LIBCPP_HAS_BITSCAN64)
+    (defined(_M_AMD64) || defined(__x86_64__))
+  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>(__x)))
+    return where;
+  // Scan the High Word.
+  if (_BitScanForward(&where, static_cast<unsigned long>(__x >> 32)))
+    return where + 32; // Create a bit offset from the LSB.
+#endif
+  return 64;
+#endif // _LIBCPP_COMPILER_MSVC
+}
+
+// Precondition:  __x != 0
+inline _LIBCPP_INLINE_VISIBILITY
+unsigned __clz(unsigned __x) {
+#ifndef _LIBCPP_COMPILER_MSVC
+    return static_cast<unsigned>(__builtin_clz(__x));
+#else
+  static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
+  static_assert(sizeof(unsigned long) == 4, "");
+  unsigned long where;
+  // Search from LSB to MSB for first set bit.
+  // Returns zero if no set bit is found.
+  if (_BitScanReverse(&where, __x))
+    return 31 - where;
+  return 32; // Undefined Behavior.
+#endif
+}
+
+inline _LIBCPP_INLINE_VISIBILITY
+unsigned long __clz(unsigned long __x) {
+#ifndef _LIBCPP_COMPILER_MSVC
+    return static_cast<unsigned long>(__builtin_clzl (__x));
+#else
+    static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
+    return __clz(static_cast<unsigned>(__x));
+#endif
+}
+
+inline _LIBCPP_INLINE_VISIBILITY
+unsigned long long __clz(unsigned long long __x) {
+#ifndef _LIBCPP_COMPILER_MSVC
+    return static_cast<unsigned long long>(__builtin_clzll(__x));
+#else
+  unsigned long where;
+// 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, __x))
+    return static_cast<int>(63 - where);
+#else
+  // Scan the high 32 bits.
+  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>(__x)))
+    return 63 - where;
+#endif
+  return 64; // Undefined Behavior.
+#endif // _LIBCPP_COMPILER_MSVC
+}
+
+inline _LIBCPP_INLINE_VISIBILITY int __pop_count(unsigned __x) {
+#ifndef _LIBCPP_COMPILER_MSVC
+  return __builtin_popcount  (__x);
+#else
+  static_assert(sizeof(unsigned) == 4, "");
+  return __popcnt(__x);
+#endif
+}
+
+inline _LIBCPP_INLINE_VISIBILITY int __pop_count(unsigned long __x) {
+#ifndef _LIBCPP_COMPILER_MSVC
+  return __builtin_popcountl (__x);
+#else
+  static_assert(sizeof(unsigned long) == 4, "");
+  return __popcnt(__x);
+#endif
+}
+
+inline _LIBCPP_INLINE_VISIBILITY int __pop_count(unsigned long long __x) {
+#ifndef _LIBCPP_COMPILER_MSVC
+  return __builtin_popcountll(__x);
+#else
+  static_assert(sizeof(unsigned long long) == 8, "");
+  return __popcnt64(__x);
+#endif
+}
+
 // all_of
 
 template <class _InputIterator, class _Predicate>