[libcxx-commits] [libcxx] [libc++][SIMD] Add native SIMD width detection for HVX (PR #183432)

[via libcxx-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libcxx

Author: Brian Cain (androm3da)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/183432.diff


4 Files Affected:

- (modified) libcxx/include/__cxx03/experimental/__config (+6-1) 
- (modified) libcxx/include/experimental/__simd/declaration.h (+6-1) 
- (modified) libcxx/include/experimental/__simd/vec_ext.h (+2-1) 
- (added) libcxx/test/std/experimental/simd/simd.traits/simd_size_hvx.pass.cpp (+45) 


``````````diff
diff --git a/libcxx/include/__cxx03/experimental/__config b/libcxx/include/__cxx03/experimental/__config
index 027522ed35771..71ec7f5dd9503 100644
--- a/libcxx/include/__cxx03/experimental/__config
+++ b/libcxx/include/__cxx03/experimental/__config
@@ -36,7 +36,12 @@
   }
 
 // TODO: support more targets
-#if defined(__AVX__)
+#if defined(__HVX__)
+#  if __HVX_LENGTH__ != 128
+#    error "Only 128-byte HVX vectors are supported by <experimental/simd>"
+#  endif
+#  define _LIBCPP_NATIVE_SIMD_WIDTH_IN_BYTES 128
+#elif defined(__AVX__)
 #  define _LIBCPP_NATIVE_SIMD_WIDTH_IN_BYTES 32
 #else
 #  define _LIBCPP_NATIVE_SIMD_WIDTH_IN_BYTES 16
diff --git a/libcxx/include/experimental/__simd/declaration.h b/libcxx/include/experimental/__simd/declaration.h
index d9395baecfe0f..88751c5586cb2 100644
--- a/libcxx/include/experimental/__simd/declaration.h
+++ b/libcxx/include/experimental/__simd/declaration.h
@@ -16,7 +16,12 @@
 #if _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
 
 // TODO: support more targets
-#  if defined(__AVX__)
+#  if defined(__HVX__)
+#    if __HVX_LENGTH__ != 128
+#      error "Only 128-byte HVX vectors are supported by <experimental/simd>"
+#    endif
+#    define _LIBCPP_NATIVE_SIMD_WIDTH_IN_BYTES 128
+#  elif defined(__AVX__)
 #    define _LIBCPP_NATIVE_SIMD_WIDTH_IN_BYTES 32
 #  else
 #    define _LIBCPP_NATIVE_SIMD_WIDTH_IN_BYTES 16
diff --git a/libcxx/include/experimental/__simd/vec_ext.h b/libcxx/include/experimental/__simd/vec_ext.h
index 2a4b8c748f86d..9bd806f098b0c 100644
--- a/libcxx/include/experimental/__simd/vec_ext.h
+++ b/libcxx/include/experimental/__simd/vec_ext.h
@@ -33,7 +33,8 @@ struct __vec_ext {
 } // namespace simd_abi
 
 template <int _Np>
-inline constexpr bool is_abi_tag_v<simd_abi::__vec_ext<_Np>> = _Np > 0 && _Np <= 32;
+inline constexpr bool is_abi_tag_v<simd_abi::__vec_ext<_Np>> =
+    _Np > 0 && _Np <= (_LIBCPP_NATIVE_SIMD_WIDTH_IN_BYTES > 32 ? _LIBCPP_NATIVE_SIMD_WIDTH_IN_BYTES : 32);
 
 template <class _Tp, int _Np>
 struct __simd_storage<_Tp, simd_abi::__vec_ext<_Np>> {
diff --git a/libcxx/test/std/experimental/simd/simd.traits/simd_size_hvx.pass.cpp b/libcxx/test/std/experimental/simd/simd.traits/simd_size_hvx.pass.cpp
new file mode 100644
index 0000000000000..9887081e5da00
--- /dev/null
+++ b/libcxx/test/std/experimental/simd/simd.traits/simd_size_hvx.pass.cpp
@@ -0,0 +1,45 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14
+// REQUIRES: hexagon-registered-target
+// ADDITIONAL_COMPILE_FLAGS: -mhvx
+
+// <experimental/simd>
+//
+// [simd.traits]
+// Verify that native_simd sizes match the 128-byte HVX vector register
+// width.  This mirrors the checks in simd_size.pass.cpp for the native
+// ABI but with concrete HVX expectations.
+
+#include "../test_utils.h"
+
+namespace ex = std::experimental::parallelism_v2;
+
+static_assert(_LIBCPP_NATIVE_SIMD_WIDTH_IN_BYTES == 128, "HVX native SIMD width must be 128 bytes");
+
+struct CheckHvxNativeSimdSize {
+  template <class T>
+  void operator()() {
+    constexpr std::size_t expected = 128 / sizeof(T);
+
+    static_assert(ex::simd_size_v<T, ex::simd_abi::native<T>> == expected);
+    static_assert(ex::simd_size<T, ex::simd_abi::native<T>>::value == expected);
+    static_assert(ex::native_simd<T>::size() == expected);
+    static_assert(ex::is_abi_tag_v<ex::simd_abi::native<T>>);
+
+    // memory_alignment for native should be 128 bytes (one HVX register)
+    if constexpr (!std::is_same_v<T, long double>)
+      static_assert(ex::memory_alignment_v<ex::native_simd<T>> == 128);
+  }
+};
+
+int main(int, char**) {
+  types::for_each(arithmetic_no_bool_types(), CheckHvxNativeSimdSize());
+  return 0;
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/183432