Re-apply "[libcxx] implement <simd> ABI for Clang/GCC vector extension, constructors, copy_from and copy_to."

...with proper guarding #ifdefs for unsupported C++11.

llvm-svn: 338318
diff --git a/libcxx/test/std/experimental/simd/simd.mem/load.pass.cpp b/libcxx/test/std/experimental/simd/simd.mem/load.pass.cpp
new file mode 100644
index 0000000..b1a3a2b
--- /dev/null
+++ b/libcxx/test/std/experimental/simd/simd.mem/load.pass.cpp
@@ -0,0 +1,122 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+// <experimental/simd>
+//
+// loads [simd.load]
+// template <class U, class Flags> void copy_from(const U* mem, Flags f);
+
+#include <experimental/simd>
+#include <cstdint>
+
+#include "test_macros.h"
+
+namespace ex = std::experimental::parallelism_v2;
+
+template <class T, class... Args>
+auto not_supported_load(Args&&... args) -> decltype(
+    std::declval<ex::native_simd<T>>().copy_from(std::forward<Args>(args)...),
+    void()) = delete;
+
+template <class T>
+void not_supported_load(...) {}
+
+template <class T, class... Args>
+auto supported_load(Args&&... args) -> decltype(
+    std::declval<ex::native_simd<T>>().copy_from(std::forward<Args>(args)...),
+    void()) {}
+
+template <class T>
+void supported_load(...) = delete;
+
+void compile_load() {
+  supported_load<int>((int*)nullptr, ex::element_aligned_tag());
+  supported_load<uint32_t>((int*)nullptr, ex::element_aligned_tag());
+  supported_load<double>((float*)nullptr, ex::element_aligned_tag());
+  supported_load<uint16_t>((unsigned int*)nullptr, ex::element_aligned_tag());
+  supported_load<uint32_t>((float*)nullptr, ex::element_aligned_tag());
+
+  not_supported_load<int>((int*)nullptr, int());
+}
+
+template <typename SimdType>
+void test_load() {
+  alignas(32) int32_t buffer[] = {4, 3, 2, 1};
+  {
+    SimdType a;
+    a.copy_from(buffer, ex::element_aligned_tag());
+    assert(a[0] == 4);
+    assert(a[1] == 3);
+    assert(a[2] == 2);
+    assert(a[3] == 1);
+  }
+  {
+    SimdType a;
+    a.copy_from(buffer, ex::vector_aligned_tag());
+    assert(a[0] == 4);
+    assert(a[1] == 3);
+    assert(a[2] == 2);
+    assert(a[3] == 1);
+  }
+  {
+    SimdType a;
+    a.copy_from(buffer, ex::overaligned_tag<32>());
+    assert(a[0] == 4);
+    assert(a[1] == 3);
+    assert(a[2] == 2);
+    assert(a[3] == 1);
+  }
+
+  {
+    SimdType a;
+    a.copy_from(buffer, ex::element_aligned);
+    assert(a[0] == 4);
+    assert(a[1] == 3);
+    assert(a[2] == 2);
+    assert(a[3] == 1);
+  }
+  {
+    SimdType a;
+    a.copy_from(buffer, ex::vector_aligned);
+    assert(a[0] == 4);
+    assert(a[1] == 3);
+    assert(a[2] == 2);
+    assert(a[3] == 1);
+  }
+  {
+    SimdType a;
+    a.copy_from(buffer, ex::overaligned<32>);
+    assert(a[0] == 4);
+    assert(a[1] == 3);
+    assert(a[2] == 2);
+    assert(a[3] == 1);
+  }
+}
+
+template <typename SimdType>
+void test_converting_load() {
+  float buffer[] = {1., 2., 4., 8.};
+  SimdType a;
+  a.copy_from(buffer, ex::element_aligned_tag());
+  assert(a[0] == 1);
+  assert(a[1] == 2);
+  assert(a[2] == 4);
+  assert(a[3] == 8);
+}
+
+int main() {
+  // TODO: adjust the tests when this assertion fails.
+  assert(ex::native_simd<int32_t>::size() >= 4);
+  test_load<ex::native_simd<int32_t>>();
+  test_load<ex::fixed_size_simd<int32_t, 4>>();
+  test_converting_load<ex::native_simd<int32_t>>();
+  test_converting_load<ex::fixed_size_simd<int32_t, 4>>();
+}