[gcc r12-1782] libstdc++: Improve simd fixed_size codegen

[Jonathan Wakely]

https://gcc.gnu.org/g:343f01f4cde17003b6721722361e190bd6cffd15

commit r12-1782-g343f01f4cde17003b6721722361e190bd6cffd15
Author: Matthias Kretz <m.kretz@gsi.de>
Date:   Thu Jun 24 14:20:14 2021 +0100

    libstdc++: Improve simd fixed_size codegen
    
    Sometimes fixed_size objects will get unnecessarily copied on the stack.
    The simd implementation should never pass _SimdTuple by value to avoid
    requiring the optimizer to see through these copies.
    
    Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
    
    libstdc++-v3/ChangeLog:
    
            * include/experimental/bits/simd_converter.h
            (_SimdConverter::operator()): Pass _SimdTuple by const-ref.
            * include/experimental/bits/simd_fixed_size.h
            (_GLIBCXX_SIMD_FIXED_OP): Pass binary operator _SimdTuple
            arguments by const-ref.
            (_S_masked_unary): Pass _SimdTuple by const-ref.

Diff:
---
 libstdc++-v3/include/experimental/bits/simd_converter.h  | 2 +-
 libstdc++-v3/include/experimental/bits/simd_fixed_size.h | 5 ++---
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/libstdc++-v3/include/experimental/bits/simd_converter.h b/libstdc++-v3/include/experimental/bits/simd_converter.h
index 9c8bf382df9..11999df25e4 100644
--- a/libstdc++-v3/include/experimental/bits/simd_converter.h
+++ b/libstdc++-v3/include/experimental/bits/simd_converter.h
@@ -316,7 +316,7 @@ template <typename _From, int _Np, typename _To, typename _Ap>
 
     _GLIBCXX_SIMD_INTRINSIC constexpr
       typename _SimdTraits<_To, _Ap>::_SimdMember
-      operator()(_Arg __x) const noexcept
+      operator()(const _Arg& __x) const noexcept
     {
       if constexpr (_Arg::_S_tuple_size == 1)
 	return __vector_convert<__vector_type_t<_To, _Np>>(__x.first);
diff --git a/libstdc++-v3/include/experimental/bits/simd_fixed_size.h b/libstdc++-v3/include/experimental/bits/simd_fixed_size.h
index b6fb47cdf39..dc2fb90b9b2 100644
--- a/libstdc++-v3/include/experimental/bits/simd_fixed_size.h
+++ b/libstdc++-v3/include/experimental/bits/simd_fixed_size.h
@@ -1480,7 +1480,7 @@ template <int _Np>
 #define _GLIBCXX_SIMD_FIXED_OP(name_, op_)                                     \
     template <typename _Tp, typename... _As>                                   \
       static inline constexpr _SimdTuple<_Tp, _As...> name_(                   \
-	const _SimdTuple<_Tp, _As...> __x, const _SimdTuple<_Tp, _As...> __y)  \
+	const _SimdTuple<_Tp, _As...>& __x, const _SimdTuple<_Tp, _As...>& __y)\
       {                                                                        \
 	return __x._M_apply_per_chunk(                                         \
 	  [](auto __impl, auto __xx, auto __yy) constexpr {                    \
@@ -1780,8 +1780,7 @@ template <int _Np>
     // _S_masked_unary {{{2
     template <template <typename> class _Op, typename _Tp, typename... _As>
       static inline _SimdTuple<_Tp, _As...>
-      _S_masked_unary(const _MaskMember __bits,
-		      const _SimdTuple<_Tp, _As...> __v) // TODO: const-ref __v?
+      _S_masked_unary(const _MaskMember __bits, const _SimdTuple<_Tp, _As...>& __v)
       {
 	return __v._M_apply_wrapped([&__bits](auto __meta,
 					      auto __native) constexpr {