Fixed compilation on mingw.

include/private/SkTLogic.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  *
  *
  * This header provides some of the helpers (like std::enable_if_t) which will
  * become available with C++14 in the type_traits header (in the skstd
  * namespace). This header also provides several Skia specific additions such
@@ skipping 31 matching lines @@
 // On all platforms, variadic functions only exist in the c calling convention.
 // mcvc 2013 introduced __vectorcall, but it wan't until 2015 that it was added to is_function.
 template <typename> struct is_function : std::false_type {};
 #if !defined(SK_BUILD_FOR_WIN)
 template <typename R, typename... Args> struct is_function<R(Args...)> : std::true_type {};
 #else
 #if defined(_M_IX86)
 template <typename R, typename... Args> struct is_function<R __cdecl (Args...)> : std::true_type {};
 template <typename R, typename... Args> struct is_function<R __stdcall (Args...)> : std::true_type {};
 template <typename R, typename... Args> struct is_function<R __fastcall (Args...)> : std::true_type {};
-#if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
+#if defined(_MSC_VER) && SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
 template <typename R, typename... Args> struct is_function<R __vectorcall (Args...)> : std::true_type {};
 #endif
 #else
 template <typename R, typename... Args> struct is_function<R __cdecl (Args...)> : std::true_type {};
+#if defined(_MSC_VER)
 template <typename R, typename... Args> struct is_function<R __vectorcall (Args...)> : std::true_type {};
 #endif
 #endif
+#endif

[bungeman-skia, 2016/01/14 18:04:58]

I would really like to avoid another nesting ifdef here, it's getting hard to
read. This was originally structured on the idea that it would be clearer to
have each individual platform (or set of calling conventions) in one block. As
it turns out, this is a bit of a mess. I think it's clearer to restructure this,
replacing the above lines 48 to 60 with

template <typename R, typename... Args> struct is_function<R __cdecl (Args...)>
: std::true_type {};
#  if defined(_M_IX86)
template <typename R, typename... Args> struct is_function<R __stdcall
(Args...)> : std::true_type {};
template <typename R, typename... Args> struct is_function<R __fastcall
(Args...)> : std::true_type {};
#  endif
#  if defined(_MSC_VER) && (SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2)
template <typename R, typename... Args> struct is_function<R __vectorcall
(Args...)> : std::true_type {};
#  endif

 template <typename R, typename... Args> struct is_function<R(Args..., ...)> : std::true_type {};
 
 template <typename T> using add_const_t = typename std::add_const<T>::type;
 template <typename T> using add_volatile_t = typename std::add_volatile<T>::type;
 template <typename T> using add_cv_t = typename std::add_cv<T>::type;
 template <typename T> using add_pointer_t = typename std::add_pointer<T>::type;
 template <typename T> using add_lvalue_reference_t = typename std::add_lvalue_reference<T>::type;
 
 template <typename S, typename D,
           bool=std::is_void<S>::value || is_function<D>::value || std::is_array<D>::value>
@@ skipping 51 matching lines @@
 template <typename D, typename S> using same_volatile_t = typename same_volatile<D, S>::type;
 template <typename D, typename S> using same_cv = copy_cv<skstd::remove_cv_t<D>, S>;
 template <typename D, typename S> using same_cv_t = typename same_cv<D, S>::type;
 
 }  // namespace sknonstd
 
 // Just a pithier wrapper for enable_if_t.
 #define SK_WHEN(condition, T) skstd::enable_if_t<!!(condition), T>
 
 #endif