Merge clang, llvm, lld, lldb, compiler-rt and libc++ 5.0.0 release.

MFC r309126 (by emaste):

  Correct lld llvm-tblgen dependency file name

MFC r309169:

  Get rid of separate Subversion mergeinfo properties for llvm-dwarfdump
  and llvm-lto.  The mergeinfo confuses Subversion enormously, and these
  directories will just use the mergeinfo for llvm itself.

MFC r312765:

  Pull in r276136 from upstream llvm trunk (by Wei Mi):

    Use ValueOffsetPair to enhance value reuse during SCEV expansion.

    In D12090, the ExprValueMap was added to reuse existing value during
    SCEV expansion. However, const folding and sext/zext distribution can
    make the reuse still difficult.

    A simplified case is: suppose we know S1 expands to V1 in
    ExprValueMap, and
      S1 = S2 + C_a
      S3 = S2 + C_b
    where C_a and C_b are different SCEVConstants. Then we'd like to
    expand S3 as V1 - C_a + C_b instead of expanding S2 literally. It is
    helpful when S2 is a complex SCEV expr and S2 has no entry in
    ExprValueMap, which is usually caused by the fact that S3 is
    generated from S1 after const folding.

    In order to do that, we represent ExprValueMap as a mapping from SCEV
    to ValueOffsetPair. We will save both S1->{V1, 0} and S2->{V1, C_a}
    into the ExprValueMap when we create SCEV for V1. When S3 is
    expanded, it will first expand S2 to V1 - C_a because of S2->{V1,
    C_a} in the map, then expand S3 to V1 - C_a + C_b.

    Differential Revision: https://reviews.llvm.org/D21313

  This should fix assertion failures when building OpenCV >= 3.1.

  PR:		215649

MFC r312831:

  Revert r312765 for now, since it causes assertions when building
  lang/spidermonkey24.

  Reported by:	antoine
  PR:		215649

MFC r316511 (by jhb):

  Add an implementation of __ffssi2() derived from __ffsdi2().

  Newer versions of GCC include an __ffssi2() symbol in libgcc and the
  compiler can emit calls to it in generated code.  This is true for at
  least GCC 6.2 when compiling world for mips and mips64.

  Reviewed by:	jmallett, dim
  Sponsored by:	DARPA / AFRL
  Differential Revision:	https://reviews.freebsd.org/D10086

MFC r318601 (by adrian):

  [libcompiler-rt] add bswapdi2/bswapsi2

  This is required for mips gcc 6.3 userland to build/run.

  Reviewed by:	emaste, dim
  Approved by:	emaste
  Differential Revision:	https://reviews.freebsd.org/D10838

MFC r318884 (by emaste):

  lldb: map TRAP_CAP to a trace trap

  In the absense of a more specific handler for TRAP_CAP (generated by
  ENOTCAPABLE or ECAPMODE while in capability mode) treat it as a trace
  trap.

  Example usage (testing the bug in PR219173):

  % proccontrol -m trapcap lldb usr.bin/hexdump/obj/hexdump -- -Cv -s 1 /bin/ls
  ...
  (lldb) run
  Process 12980 launching
  Process 12980 launched: '.../usr.bin/hexdump/obj/hexdump' (x86_64)
  Process 12980 stopped
  * thread #1, stop reason = trace
      frame #0: 0x0000004b80c65f1a libc.so.7`__sys_lseek + 10
  ...

  In the future we should have LLDB control the trapcap procctl itself
  (as it does with ASLR), as well as report a specific stop reason.
  This change eliminates an assertion failure from LLDB for now.

MFC r319796:

  Remove a few unneeded files from libllvm, libclang and liblldb.

MFC r319885 (by emaste):

  lld: ELF: Fix ICF crash on absolute symbol relocations.

  If two sections contained relocations to absolute symbols with the same
  value we would crash when trying to access their sections. Add a check that
  both symbols point to sections before accessing their sections, and treat
  absolute symbols as equal if their values are equal.

  Obtained from:	LLD commit r292578

MFC r319918:

  Revert r319796 for now, it can cause undefined references when linking
  in some circumstances.

  Reported by:	Shawn Webb <shawn.webb@hardenedbsd.org>

MFC r319957 (by emaste):

  lld: Add armelf emulation mode

  Obtained from:	LLD r305375

MFC r321369:

  Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
  5.0.0 (trunk r308421).  Upstream has branched for the 5.0.0 release,
  which should be in about a month.  Please report bugs and regressions,
  so we can get them into the release.

  Please note that from 3.5.0 onwards, clang, llvm and lldb require C++11
  support to build; see UPDATING for more information.

MFC r321420:

  Add a few more object files to liblldb, which should solve errors when
  linking the lldb executable in some cases.  In particular, when the
  -ffunction-sections -fdata-sections options are turned off, or
  ineffective.

  Reported by:	Shawn Webb, Mark Millard

MFC r321433:

  Cleanup stale Options.inc files from the previous libllvm build for
  clang 4.0.0.  Otherwise, these can get included before the two newly
  generated ones (which are different) for clang 5.0.0.

  Reported by:	Mark Millard

MFC r321439 (by bdrewery):

  Move llvm Options.inc hack from r321433 for NO_CLEAN to lib/clang/libllvm.

  The files are only ever generated to .OBJDIR, not to WORLDTMP (as a
  sysroot) and are only ever included from a compilation.  So using
  a beforebuild target here removes the file before the compilation
  tries to include it.

MFC r321664:

  Pull in r308891 from upstream llvm trunk (by Benjamin Kramer):

    [CodeGenPrepare] Cut off FindAllMemoryUses if there are too many uses.

    This avoids excessive compile time. The case I'm looking at is
    Function.cpp from an old version of LLVM that still had the giant
    memcmp string matcher in it. Before r308322 this compiled in about 2
    minutes, after it, clang takes infinite* time to compile it. With
    this patch we're at 5 min, which is still bad but this is a
    pathological case.

    The cut off at 20 uses was chosen by looking at other cut-offs in LLVM
    for user scanning. It's probably too high, but does the job and is
    very unlikely to regress anything.

    Fixes PR33900.

    * I'm impatient and aborted after 15 minutes, on the bug report it was
      killed after 2h.

  Pull in r308986 from upstream llvm trunk (by Simon Pilgrim):

    [X86][CGP] Reduce memcmp() expansion to 2 load pairs (PR33914)

    D35067/rL308322 attempted to support up to 4 load pairs for memcmp
    inlining which resulted in regressions for some optimized libc memcmp
    implementations (PR33914).

    Until we can match these more optimal cases, this patch reduces the
    memcmp expansion to a maximum of 2 load pairs (which matches what we
    do for -Os).

    This patch should be considered for the 5.0.0 release branch as well

    Differential Revision: https://reviews.llvm.org/D35830

  These fix a hang (or extremely long compile time) when building older
  LLVM ports.

  Reported by:    antoine
  PR:             219139

MFC r321719:

  Pull in r309503 from upstream clang trunk (by Richard Smith):

    PR33902: Invalidate line number cache when adding more text to
    existing buffer.

    This led to crashes as the line number cache would report a bogus
    line number for a line of code, and we'd try to find a nonexistent
    column within the line when printing diagnostics.

  This fixes an assertion when building the graphics/champlain port.

  Reported by:	antoine, kwm
  PR:		219139

MFC r321723:

  Upgrade our copies of clang, llvm, lld and lldb to r309439 from the
  upstream release_50 branch.  This is just after upstream's 5.0.0-rc1.

MFC r322320:

  Upgrade our copies of clang, llvm and libc++ to r310316 from the
  upstream release_50 branch.

MFC r322326 (by emaste):

  lldb: Make i386-*-freebsd expression work on JIT path

  * Enable i386 ABI creation for freebsd
  * Added an extra argument in ABISysV_i386::PrepareTrivialCall for mmap
    syscall
  * Unlike linux, the last argument of mmap is actually 64-bit(off_t).
    This requires us to push an additional word for the higher order bits.
  * Prior to this change, ktrace dump will show mmap failures due to
    invalid argument coming from the 6th mmap argument.

  Submitted by:	Karnajit Wangkhem
  Differential Revision:	https://reviews.llvm.org/D34776

MFC r322360 (by emaste):

  lldb: Report inferior signals as signals, not exceptions, on FreeBSD

  This is the FreeBSD equivalent of LLVM r238549.

  This serves 2 purposes:

  * LLDB should handle inferior process signals SIGSEGV/SIGILL/SIGBUS/
    SIGFPE the way it is suppose to be handled. Prior to this fix these
    signals will neither create a coredump, nor exit from the debugger
    or work for signal handling scenario.
  * eInvalidCrashReason need not report "unknown crash reason" if we have
    a valid si_signo

  llvm.org/pr23699

  Patch by Karnajit Wangkhem

  Differential Revision:  https://reviews.llvm.org/D35223

  Submitted by:	Karnajit Wangkhem
  Obtained from:	LLVM r310591

MFC r322474 (by emaste):

  lld: Add `-z muldefs` option.

  Obtained from:	LLVM r310757

MFC r322740:

  Upgrade our copies of clang, llvm, lld and libc++ to r311219 from the
  upstream release_50 branch.

MFC r322855:

  Upgrade our copies of clang, llvm, lldb and compiler-rt to r311606 from
  the upstream release_50 branch.

  As of this version, lib/msun's trig test should also work correctly
  again (see bug 220989 for more information).

  PR:		220989

MFC r323112:

  Upgrade our copies of clang, llvm, lldb and compiler-rt to r312293 from
  the upstream release_50 branch.  This corresponds to 5.0.0 rc4.

  As of this version, the cad/stepcode port should now compile in a more
  reasonable time on i386 (see bug 221836 for more information).

  PR:		221836

MFC r323245:

  Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
  5.0.0 release (upstream r312559).

  Release notes for llvm, clang and lld will be available here soon:
  <http://releases.llvm.org/5.0.0/docs/ReleaseNotes.html>
  <http://releases.llvm.org/5.0.0/tools/clang/docs/ReleaseNotes.html>
  <http://releases.llvm.org/5.0.0/tools/lld/docs/ReleaseNotes.html>

  Relnotes:	yes

1 files changed, 60 insertions, 50 deletions

diff --git a/contrib/libc++/include/tuple b/contrib/libc++/include/tuple
index cddb709..a52b934 100644
--- a/contrib/libc++/include/tuple
+++ b/contrib/libc++/include/tuple
@@ -148,7 +148,7 @@ template <class... Types>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
 
 
 // __tuple_leaf
@@ -169,7 +169,7 @@ void swap(__tuple_leaf<_Ip, _Hp, _Ep>& __x, __tuple_leaf<_Ip, _Hp, _Ep>& __y)
 template <size_t _Ip, class _Hp, bool>
 class __tuple_leaf
 {
-    _Hp value;
+    _Hp __value_;
 
     template <class _Tp>
     static constexpr bool __can_bind_reference() {
@@ -188,28 +188,28 @@ class __tuple_leaf
     __tuple_leaf& operator=(const __tuple_leaf&);
 public:
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR __tuple_leaf()
-             _NOEXCEPT_(is_nothrow_default_constructible<_Hp>::value) : value()
+             _NOEXCEPT_(is_nothrow_default_constructible<_Hp>::value) : __value_()
        {static_assert(!is_reference<_Hp>::value,
               "Attempted to default construct a reference element in a tuple");}
 
     template <class _Alloc>
         _LIBCPP_INLINE_VISIBILITY
         __tuple_leaf(integral_constant<int, 0>, const _Alloc&)
-            : value()
+            : __value_()
         {static_assert(!is_reference<_Hp>::value,
               "Attempted to default construct a reference element in a tuple");}
 
     template <class _Alloc>
         _LIBCPP_INLINE_VISIBILITY
         __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a)
-            : value(allocator_arg_t(), __a)
+            : __value_(allocator_arg_t(), __a)
         {static_assert(!is_reference<_Hp>::value,
               "Attempted to default construct a reference element in a tuple");}
 
     template <class _Alloc>
         _LIBCPP_INLINE_VISIBILITY
         __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a)
-            : value(__a)
+            : __value_(__a)
         {static_assert(!is_reference<_Hp>::value,
               "Attempted to default construct a reference element in a tuple");}
 
@@ -223,28 +223,28 @@ public:
             >
         _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
         explicit __tuple_leaf(_Tp&& __t) _NOEXCEPT_((is_nothrow_constructible<_Hp, _Tp>::value))
-            : value(_VSTD::forward<_Tp>(__t))
+            : __value_(_VSTD::forward<_Tp>(__t))
         {static_assert(__can_bind_reference<_Tp>(),
        "Attempted to construct a reference element in a tuple with an rvalue");}
 
     template <class _Tp, class _Alloc>
         _LIBCPP_INLINE_VISIBILITY
         explicit __tuple_leaf(integral_constant<int, 0>, const _Alloc&, _Tp&& __t)
-            : value(_VSTD::forward<_Tp>(__t))
+            : __value_(_VSTD::forward<_Tp>(__t))
         {static_assert(__can_bind_reference<_Tp>(),
        "Attempted to construct a reference element in a tuple with an rvalue");}
 
     template <class _Tp, class _Alloc>
         _LIBCPP_INLINE_VISIBILITY
         explicit __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a, _Tp&& __t)
-            : value(allocator_arg_t(), __a, _VSTD::forward<_Tp>(__t))
+            : __value_(allocator_arg_t(), __a, _VSTD::forward<_Tp>(__t))
         {static_assert(!is_reference<_Hp>::value,
             "Attempted to uses-allocator construct a reference element in a tuple");}
 
     template <class _Tp, class _Alloc>
         _LIBCPP_INLINE_VISIBILITY
         explicit __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a, _Tp&& __t)
-            : value(_VSTD::forward<_Tp>(__t), __a)
+            : __value_(_VSTD::forward<_Tp>(__t), __a)
         {static_assert(!is_reference<_Hp>::value,
            "Attempted to uses-allocator construct a reference element in a tuple");}
 
@@ -256,7 +256,7 @@ public:
         __tuple_leaf&
         operator=(_Tp&& __t) _NOEXCEPT_((is_nothrow_assignable<_Hp&, _Tp>::value))
         {
-            value = _VSTD::forward<_Tp>(__t);
+            __value_ = _VSTD::forward<_Tp>(__t);
             return *this;
         }
 
@@ -267,8 +267,8 @@ public:
         return 0;
     }
 
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11       _Hp& get()       _NOEXCEPT {return value;}
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 const _Hp& get() const _NOEXCEPT {return value;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11       _Hp& get()       _NOEXCEPT {return __value_;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 const _Hp& get() const _NOEXCEPT {return __value_;}
 };
 
 template <size_t _Ip, class _Hp>
@@ -366,7 +366,7 @@ struct __all_default_constructible<__tuple_types<_Tp...>>
 template<class _Indx, class ..._Tp> struct __tuple_impl;
 
 template<size_t ..._Indx, class ..._Tp>
-struct __tuple_impl<__tuple_indices<_Indx...>, _Tp...>
+struct _LIBCPP_DECLSPEC_EMPTY_BASES __tuple_impl<__tuple_indices<_Indx...>, _Tp...>
     : public __tuple_leaf<_Indx, _Tp>...
 {
     _LIBCPP_INLINE_VISIBILITY
@@ -473,9 +473,9 @@ struct __tuple_impl<__tuple_indices<_Indx...>, _Tp...>
 template <class ..._Tp>
 class _LIBCPP_TEMPLATE_VIS tuple
 {
-    typedef __tuple_impl<typename __make_tuple_indices<sizeof...(_Tp)>::type, _Tp...> base;
+    typedef __tuple_impl<typename __make_tuple_indices<sizeof...(_Tp)>::type, _Tp...> _BaseT;
 
-    base base_;
+    _BaseT __base_;
 
 #if defined(_LIBCPP_ENABLE_TUPLE_IMPLICIT_REDUCED_ARITY_EXTENSION)
     static constexpr bool _EnableImplicitReducedArityExtension = true;
@@ -628,7 +628,7 @@ public:
     >::type>
     _LIBCPP_INLINE_VISIBILITY
     tuple(_AllocArgT, _Alloc const& __a)
-      : base_(allocator_arg_t(), __a,
+      : __base_(allocator_arg_t(), __a,
                     __tuple_indices<>(), __tuple_types<>(),
                     typename __make_tuple_indices<sizeof...(_Tp), 0>::type(),
                     __tuple_types<_Tp...>()) {}
@@ -644,7 +644,7 @@ public:
         >
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     tuple(const _Tp& ... __t) _NOEXCEPT_((__all<is_nothrow_copy_constructible<_Tp>::value...>::value))
-        : base_(typename __make_tuple_indices<sizeof...(_Tp)>::type(),
+        : __base_(typename __make_tuple_indices<sizeof...(_Tp)>::type(),
                 typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(),
                 typename __make_tuple_indices<0>::type(),
                 typename __make_tuple_types<tuple, 0>::type(),
@@ -662,7 +662,7 @@ public:
         >
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     explicit tuple(const _Tp& ... __t) _NOEXCEPT_((__all<is_nothrow_copy_constructible<_Tp>::value...>::value))
-        : base_(typename __make_tuple_indices<sizeof...(_Tp)>::type(),
+        : __base_(typename __make_tuple_indices<sizeof...(_Tp)>::type(),
                 typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(),
                 typename __make_tuple_indices<0>::type(),
                 typename __make_tuple_types<tuple, 0>::type(),
@@ -680,7 +680,7 @@ public:
         >
       _LIBCPP_INLINE_VISIBILITY
       tuple(allocator_arg_t, const _Alloc& __a, const _Tp& ... __t)
-        : base_(allocator_arg_t(), __a,
+        : __base_(allocator_arg_t(), __a,
                 typename __make_tuple_indices<sizeof...(_Tp)>::type(),
                 typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(),
                 typename __make_tuple_indices<0>::type(),
@@ -700,7 +700,7 @@ public:
       _LIBCPP_INLINE_VISIBILITY
       explicit
       tuple(allocator_arg_t, const _Alloc& __a, const _Tp& ... __t)
-        : base_(allocator_arg_t(), __a,
+        : __base_(allocator_arg_t(), __a,
                 typename __make_tuple_indices<sizeof...(_Tp)>::type(),
                 typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(),
                 typename __make_tuple_indices<0>::type(),
@@ -727,7 +727,7 @@ public:
         _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
         tuple(_Up&&... __u)
             _NOEXCEPT_((
-                is_nothrow_constructible<base,
+                is_nothrow_constructible<_BaseT,
                     typename __make_tuple_indices<sizeof...(_Up)>::type,
                     typename __make_tuple_types<tuple, sizeof...(_Up)>::type,
                     typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type,
@@ -735,7 +735,7 @@ public:
                     _Up...
                 >::value
             ))
-            : base_(typename __make_tuple_indices<sizeof...(_Up)>::type(),
+            : __base_(typename __make_tuple_indices<sizeof...(_Up)>::type(),
                     typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
                     typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
                     typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(),
@@ -751,7 +751,7 @@ public:
                          _CheckArgsConstructor<
                             !_EnableImplicitReducedArityExtension
                             && sizeof...(_Up) < sizeof...(_Tp)
-                            && !_PackExpandsToThisTuple<_Up...>()
+                            && !_PackExpandsToThisTuple<_Up...>::value
                          >::template __enable_implicit<_Up...>(),
                          bool
                       >::type = false
@@ -760,7 +760,7 @@ public:
         explicit
         tuple(_Up&&... __u)
             _NOEXCEPT_((
-                is_nothrow_constructible<base,
+                is_nothrow_constructible<_BaseT,
                     typename __make_tuple_indices<sizeof...(_Up)>::type,
                     typename __make_tuple_types<tuple, sizeof...(_Up)>::type,
                     typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type,
@@ -768,7 +768,7 @@ public:
                     _Up...
                 >::value
             ))
-            : base_(typename __make_tuple_indices<sizeof...(_Up)>::type(),
+            : __base_(typename __make_tuple_indices<sizeof...(_Up)>::type(),
                     typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
                     typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
                     typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(),
@@ -786,7 +786,7 @@ public:
              >
         _LIBCPP_INLINE_VISIBILITY
         tuple(allocator_arg_t, const _Alloc& __a, _Up&&... __u)
-            : base_(allocator_arg_t(), __a,
+            : __base_(allocator_arg_t(), __a,
                     typename __make_tuple_indices<sizeof...(_Up)>::type(),
                     typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
                     typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
@@ -806,7 +806,7 @@ public:
         _LIBCPP_INLINE_VISIBILITY
         explicit
         tuple(allocator_arg_t, const _Alloc& __a, _Up&&... __u)
-            : base_(allocator_arg_t(), __a,
+            : __base_(allocator_arg_t(), __a,
                     typename __make_tuple_indices<sizeof...(_Up)>::type(),
                     typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
                     typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
@@ -824,8 +824,8 @@ public:
                       >::type = false
              >
         _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        tuple(_Tuple&& __t) _NOEXCEPT_((is_nothrow_constructible<base, _Tuple>::value))
-            : base_(_VSTD::forward<_Tuple>(__t)) {}
+        tuple(_Tuple&& __t) _NOEXCEPT_((is_nothrow_constructible<_BaseT, _Tuple>::value))
+            : __base_(_VSTD::forward<_Tuple>(__t)) {}
 
     template <class _Tuple,
               typename enable_if
@@ -839,8 +839,8 @@ public:
              >
         _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
         explicit
-        tuple(_Tuple&& __t) _NOEXCEPT_((is_nothrow_constructible<base, _Tuple>::value))
-            : base_(_VSTD::forward<_Tuple>(__t)) {}
+        tuple(_Tuple&& __t) _NOEXCEPT_((is_nothrow_constructible<_BaseT, _Tuple>::value))
+            : __base_(_VSTD::forward<_Tuple>(__t)) {}
 
     template <class _Alloc, class _Tuple,
               typename enable_if
@@ -853,7 +853,7 @@ public:
              >
         _LIBCPP_INLINE_VISIBILITY
         tuple(allocator_arg_t, const _Alloc& __a, _Tuple&& __t)
-            : base_(allocator_arg_t(), __a, _VSTD::forward<_Tuple>(__t)) {}
+            : __base_(allocator_arg_t(), __a, _VSTD::forward<_Tuple>(__t)) {}
 
     template <class _Alloc, class _Tuple,
               typename enable_if
@@ -867,7 +867,7 @@ public:
         _LIBCPP_INLINE_VISIBILITY
         explicit
         tuple(allocator_arg_t, const _Alloc& __a, _Tuple&& __t)
-            : base_(allocator_arg_t(), __a, _VSTD::forward<_Tuple>(__t)) {}
+            : __base_(allocator_arg_t(), __a, _VSTD::forward<_Tuple>(__t)) {}
 
     using _CanCopyAssign = __all<is_copy_assignable<_Tp>::value...>;
     using _CanMoveAssign = __all<is_move_assignable<_Tp>::value...>;
@@ -876,7 +876,7 @@ public:
     tuple& operator=(typename conditional<_CanCopyAssign::value, tuple, __nat>::type const& __t)
         _NOEXCEPT_((__all<is_nothrow_copy_assignable<_Tp>::value...>::value))
     {
-        base_.operator=(__t.base_);
+        __base_.operator=(__t.__base_);
         return *this;
     }
 
@@ -884,7 +884,7 @@ public:
     tuple& operator=(typename conditional<_CanMoveAssign::value, tuple, __nat>::type&& __t)
         _NOEXCEPT_((__all<is_nothrow_move_assignable<_Tp>::value...>::value))
     {
-        base_.operator=(static_cast<base&&>(__t.base_));
+        __base_.operator=(static_cast<_BaseT&&>(__t.__base_));
         return *this;
     }
 
@@ -896,15 +896,15 @@ public:
              >
         _LIBCPP_INLINE_VISIBILITY
         tuple&
-        operator=(_Tuple&& __t) _NOEXCEPT_((is_nothrow_assignable<base&, _Tuple>::value))
+        operator=(_Tuple&& __t) _NOEXCEPT_((is_nothrow_assignable<_BaseT&, _Tuple>::value))
         {
-            base_.operator=(_VSTD::forward<_Tuple>(__t));
+            __base_.operator=(_VSTD::forward<_Tuple>(__t));
             return *this;
         }
 
     _LIBCPP_INLINE_VISIBILITY
     void swap(tuple& __t) _NOEXCEPT_(__all<__is_nothrow_swappable<_Tp>::value...>::value)
-        {base_.swap(__t.base_);}
+        {__base_.swap(__t.__base_);}
 };
 
 template <>
@@ -929,6 +929,16 @@ public:
     void swap(tuple&) _NOEXCEPT {}
 };
 
+#ifdef __cpp_deduction_guides
+// NOTE: These are not yet standardized, but are required to simulate the
+// implicit deduction guide that should be generated had libc++ declared the
+// tuple-like constructors "correctly"
+template <class _Alloc, class ..._Args>
+tuple(allocator_arg_t, const _Alloc&, tuple<_Args...> const&) -> tuple<_Args...>;
+template <class _Alloc, class ..._Args>
+tuple(allocator_arg_t, const _Alloc&, tuple<_Args...>&&) -> tuple<_Args...>;
+#endif
+
 template <class ..._Tp>
 inline _LIBCPP_INLINE_VISIBILITY
 typename enable_if
@@ -948,7 +958,7 @@ typename tuple_element<_Ip, tuple<_Tp...> >::type&
 get(tuple<_Tp...>& __t) _NOEXCEPT
 {
     typedef typename tuple_element<_Ip, tuple<_Tp...> >::type type;
-    return static_cast<__tuple_leaf<_Ip, type>&>(__t.base_).get();
+    return static_cast<__tuple_leaf<_Ip, type>&>(__t.__base_).get();
 }
 
 template <size_t _Ip, class ..._Tp>
@@ -957,7 +967,7 @@ const typename tuple_element<_Ip, tuple<_Tp...> >::type&
 get(const tuple<_Tp...>& __t) _NOEXCEPT
 {
     typedef typename tuple_element<_Ip, tuple<_Tp...> >::type type;
-    return static_cast<const __tuple_leaf<_Ip, type>&>(__t.base_).get();
+    return static_cast<const __tuple_leaf<_Ip, type>&>(__t.__base_).get();
 }
 
 template <size_t _Ip, class ..._Tp>
@@ -967,7 +977,7 @@ get(tuple<_Tp...>&& __t) _NOEXCEPT
 {
     typedef typename tuple_element<_Ip, tuple<_Tp...> >::type type;
     return static_cast<type&&>(
-             static_cast<__tuple_leaf<_Ip, type>&&>(__t.base_).get());
+             static_cast<__tuple_leaf<_Ip, type>&&>(__t.__base_).get());
 }
 
 template <size_t _Ip, class ..._Tp>
@@ -977,7 +987,7 @@ get(const tuple<_Tp...>&& __t) _NOEXCEPT
 {
     typedef typename tuple_element<_Ip, tuple<_Tp...> >::type type;
     return static_cast<const type&&>(
-             static_cast<const __tuple_leaf<_Ip, type>&&>(__t.base_).get());
+             static_cast<const __tuple_leaf<_Ip, type>&&>(__t.__base_).get());
 }
 
 #if _LIBCPP_STD_VER > 11
@@ -1064,11 +1074,13 @@ template <class _Up>
 struct __ignore_t
 {
     template <class _Tp>
-        _LIBCPP_INLINE_VISIBILITY
-        const __ignore_t& operator=(_Tp&&) const {return *this;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    const __ignore_t& operator=(_Tp&&) const {return *this;}
 };
 
-namespace { const __ignore_t<unsigned char> ignore = __ignore_t<unsigned char>(); }
+namespace {
+  constexpr __ignore_t<unsigned char> ignore = __ignore_t<unsigned char>();
+}
 
 template <class _Tp>
 struct __make_tuple_return_impl
@@ -1343,9 +1355,6 @@ template <class ..._Tp, class _Alloc>
 struct _LIBCPP_TEMPLATE_VIS uses_allocator<tuple<_Tp...>, _Alloc>
     : true_type {};
 
-#endif // _LIBCPP_HAS_NO_VARIADICS
-
-#ifndef _LIBCPP_CXX03_LANG
 template <class _T1, class _T2>
 template <class... _Args1, class... _Args2, size_t ..._I1, size_t ..._I2>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -1356,7 +1365,6 @@ pair<_T1, _T2>::pair(piecewise_construct_t,
       second(_VSTD::forward<_Args2>(_VSTD::get<_I2>(__second_args))...)
 {
 }
-#endif // _LIBCPP_CXX03_LANG
 
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
@@ -1402,6 +1410,8 @@ _LIBCPP_NOEXCEPT_RETURN(
 
 #endif // _LIBCPP_STD_VER > 14
 
+#endif // !defined(_LIBCPP_CXX03_LANG)
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_TUPLE