Basic: support _aligned_malloc on Windows

Use `_aligned_malloc` and `_aligned_free` on Windows as it does not have the
POSIX interfaces `posix_memalign`.  `_aligned_malloc` has an associated
`_aligned_free` instead of the normal `free` call.

Author: compnerd

include/swift/Basic/Malloc.h

@@ -23,25 +23,33 @@
 
 namespace swift {
 
-// FIXME: Use C11 aligned_alloc or Windows _aligned_malloc if available.
+// FIXME: Use C11 aligned_alloc if available.
 inline void *AlignedAlloc(size_t size, size_t align) {
   // posix_memalign only accepts alignments greater than sizeof(void*).
   // 
   if (align < sizeof(void*))
     align = sizeof(void*);
 
   void *r;
+#if defined(_WIN32)
+  r = _aligned_malloc(size, align);
+  assert(r && "_aligned_malloc failed");
+#else
   int res = posix_memalign(&r, align, size);
   assert(res == 0 && "posix_memalign failed");
   (void)res; // Silence the unused variable warning.
+#endif
   return r;
 }
-  
-// FIXME: Use Windows _aligned_free if available.
+
 inline void AlignedFree(void *p) {
+#if defined(_WIN32)
+  _aligned_free(p);
+#else
   free(p);
+#endif
 }
-  
+
 } // end namespace swift
 
 #endif // SWIFT_BASIC_MALLOC_H